Philco model 60

[John-Del]

After owning this about 40 years, I decided to restore it. Doing some Googling it seems there are several model 60 variants with later versions having factory changes done during the run. According to the website http://www.tuberadioland.com/philco60_lineage.html , there are five versions of the model 60 and three sub-versions of the third version which I believe I'm in possession of.

Mine looks like this: http://www.tuberadioland.com/myphotos/philco60_x1.gif

It has the same cabinet/speaker grille shape and the same escutcheon. The website identifies this as a "style three- early version ". This "early version" has a unique escutcheon (like mine), but my knobs look like the later versions. The knobs on mine are exactly like this one: http://www.tuberadioland.com/images/philco60_late_4.jpg . So mine has the escutcheon of a third version -early and has the knobs of one of the two later versions of version three. Whew.

I suppose it's possible this radio had the knobs changed over the years but they are at least Philco knobs from another 60 if they have been replaced.

The label inside the cabinet identifies it as a "Philco Chassis Type 60 Code 121" and the tube layout chart has "Philco Models 60 & 505" on it.

The radio is in very good cosmetic shape and in beautiful shape below the chassis. Other than a tacked in electro done probably 50 years ago judging by the capacitor used, it *might* be all original and unmolested. The only thing I've done thus far is to take apart the dial drive. I removed the three bearings and cleaned the caked on muck, cleaned the bore and bearing races, repacked it with grease and it works smooth as glass.

My main question though is what to do with the bakelite capacitor blocks. Are these generally left alone unless they need attention or must they be replaced/rebuilt as part of a prudent restoration?

John
Wolcott, CT

[Foxs Mercantile]

On 6/26/2017 2:02 PM, John-Del wrote:
> My main question though is what to do with the bakelite capacitor
> blocks.

They need to have the guts removed an new caps installed.

Typically, I remove the mounting screws, cut the capacitor leads,
Heat them up with a hot air gun, then use a drift punch to knock
the tarred caps out. Then put the new caps inside.

Pretty easy once you've done one.



--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

---
This email has been checked for viruses by AVG.
http://www.avg.com

[Peter Wieck]

A few things:

a) Ron Ramirez has a list of the capacitor blocks by part number, and all the bits in them, somewhere. There is also a book out there by another author that goes into restoration techniques as well.

b)Yes, rebuild them. I have done a couple by freezing the beasts, then popping out the guts. There are other means as well. Figure the first one will take you 20 minutes, the last one about 5.

c) Use an electrical grade (non-acetic acid) black RTV silicon to 'refill' them if you wish. DO NOT use standard RTV silicon as it will attack the contacts. Acetic acid is a holy terror on copper, tin or any other active metal.

d) And, yes, they need attention!

After all that, it is fine radio and well worth the attention. Made less than 2 miles from where I live.

Peter Wieck
Melrose Park, PA

[John-Del]

Thanks Jeff and Peter. Wow, you weren't kidding. Those caps just fell apart when they were melted out of the bakelite. This was the AC filter cap - thought I'd start there.

So far I found an open AC switch which is strange as I seem to recall that radio working the last time I played it some 30 or more years ago.

I separated the switch from the volume control and drilled out the rivets holding the switch to the volume control can. The swing arm was *really* sluggish moving against the spring (like a full second after the shaft was rotated), and I think that caused the contacts to arc. I used solvent to free up the swing arm and put contact cleaner between the two contacts and manipulated the switch a couple of dozen times and it's now pivoting immediately when the shaft is turned and reading zero ohms when closed. Time will tell if it can pass current reliably.

The volume control had a paper thin piece of phenolic material pushed under the wiper arm in order to put more pressure on the carbon track. It's jumpy on the meter when rotated but always settles down to the correct value that it should have for the rotation of the control. I've never seen this before, but this volume control doesn't have the carbon paint applied to a hard phenolic plate that is typical of later volume controls, but it appears that the carbon is painted on paper which rests between the wiper and the hard base. I suspect I'll need to replace the volume control/switch before all is said and done.

I pulled the tone switch out and replaced the two potted capacitors. I left the fixed 0.01 at that value but decided to downsize the switched 0.015 to a 0.01 because it always seems that the tone switch goes overboard making the sound muffled when engaged. I haven't potted this tone control yet so if anyone has suggestions for values I'm interested in hearing them.

I've got to put this aside for a week or so and make some money. These old radios are addictive.

Thanks for the advice.

John
Wolcott, CT

[C.Copperpot]

On Tue, 27 Jun 2017 09:49:51 -0700 (PDT), John-Del <ohg...@gmail.com>
wrote:

There's also the sheet metal encased mystery box in there. I can't
remember how many caps are in there (3 to 6) ?

[John-Del]

Yep, this has the mystery box. According to the schematic I have (which so far, matches my radio perfectly), the mystery box contains 4 capacitors that share a common ground.

I said I was going to put this aside to get to other things I needed to attend to, but I couldn't help myself and pulled apart the wet electrolytics. One was completely dry and inert and the other still had half it's liquid (which was under pressure).

I used a Dremel and cut the base of the caps off about a quarter inch up and removed the innards. With the bases free of the innards, I tested them for leakage and one of them showed significant leakage despite the fact that they had no innards. The rubber stopper at the bottom had a nice coating of slime on it that was causing the problem. I scrapped and dunked the base in solvent and dried it, and the leakage current went to zero. So if anyone is going to restuff these, they should watch out for this.

I loaded them with current production 450V caps but unfortunately, the rectifier produces 480 volts in about 3 seconds after plug in, so the caps are over-volted until the other tubes start drawing. I'm going to have to order 500V caps.

The good news is that the radio pulls in the local station with just a clip lead on the Fahnestock antenna clip.


John
Wolcott, CT

[Terry S]

You'll be fine John, the voltage ratings are conservative on 'lytics by at least 20%. I wouldn't worry.

Terry

[John-Del]

On Wednesday, June 28, 2017 at 6:01:21 PM UTC-4, Terry S wrote:

> >
> > I said I was going to put this aside to get to other things I needed to attend to, but I couldn't help myself and pulled apart the wet electrolytics. One was completely dry and inert and the other still had half it's liquid (which was under pressure).
> >
> > I used a Dremel and cut the base of the caps off about a quarter inch up and removed the innards. With the bases free of the innards, I tested them for leakage and one of them showed significant leakage despite the fact that they had no innards. The rubber stopper at the bottom had a nice coating of slime on it that was causing the problem. I scrapped and dunked the base in solvent and dried it, and the leakage current went to zero. So if anyone is going to restuff these, they should watch out for this.
> >
> > I loaded them with current production 450V caps but unfortunately, the rectifier produces 480 volts in about 3 seconds after plug in, so the caps are over-volted until the other tubes start drawing. I'm going to have to order 500V caps.
> >
> > The good news is that the radio pulls in the local station with just a clip lead on the Fahnestock antenna clip.
> >
> >
> > John
> > Wolcott, CT


>
> You'll be fine John, the voltage ratings are conservative on 'lytics by at least 20%. I wouldn't worry.
>
> Terry

Thanks Terry. I guess I'll leave those 450s in there.

The radio was playing great picking up the distant stations I use for reference with just a 6' wire for an antenna, but then it lost is distance capability and just the locals came in. It had done this a couple of times and seemed a bit shock sensitive, but I thought it might be an intermittent tube or tube socket contact issue, but it stopped becoming shocks sensitive and lost is sensitivity.

Putting my finger on the tuner input doubled the volume, so I checked the antenna coil, and the lower ground section of the input winding was open. I pulled the coil and the open section fortunately was wound on the outside of the secondary and easy to get to. Unwinding the coil revealed the wire just falling apart in several places. I replaced the winding and it now reads correctly, at least continuity-wise.

What are the prospects of the rest of the coil crapping at some point? I'm concerned because this radio is clean as a whistle with no indication of rust or corrosion anywhere, yet that winding was corroded. If it's likely to give more trouble I'd be more inclined to sub the entire coil for something else.

Also, there is a plastic barrier/guide glued over the bottom of the secondary where the primary coil (the section that opened) is wound. Is it better to remove this guide and clean underneath and re-lacquer it to forestall the secondary from failing or is rewinding the secondary usually the end of trouble?

Thanks again for the advice guys. I really do have to get this off my bench to save for another day but I can't tear myself away from it!

John
Wolcott, CT

[cl...@snyder.on.ca]

On Thu, 29 Jun 2017 12:21:08 -0700 (PDT), John-Del <ohg...@gmail.com>
wrote:

>On Wednesday, June 28, 2017 at 6:01:21 PM UTC-4, Terry S wrote:
>
>> >
>> > I said I was going to put this aside to get to other things I needed to attend to, but I couldn't help myself and pulled apart the wet electrolytics. One was completely dry and inert and the other still had half it's liquid (which was under pressure).
>> >
>> > I used a Dremel and cut the base of the caps off about a quarter inch up and removed the innards. With the bases free of the innards, I tested them for leakage and one of them showed significant leakage despite the fact that they had no innards. The rubber stopper at the bottom had a nice coating of slime on it that was causing the problem. I scrapped and dunked the base in solvent and dried it, and the leakage current went to zero. So if anyone is going to restuff these, they should watch out for this.
>> >
>> > I loaded them with current production 450V caps but unfortunately, the rectifier produces 480 volts in about 3 seconds after plug in, so the caps are over-volted until the other tubes start drawing. I'm going to have to order 500V caps.
>> >
>> > The good news is that the radio pulls in the local station with just a clip lead on the Fahnestock antenna clip.
>> >
>> >
>> > John
>> > Wolcott, CT
>
>
>>
>> You'll be fine John, the voltage ratings are conservative on 'lytics by at least 20%. I wouldn't worry.
>>
>> Terry
>
>
>
>Thanks Terry. I guess I'll leave those 450s in there.

They WILL take the voltage for a while, but they will NOT last nearly
as lonmg as the right caps. A 600 volt cap will likely last 2-4 times
as long as the 450.

[Terry S]

What does the voltage drop to and settle in at? That's the real question.

I agree running 'lytics at or near their ratings for anything other than brief periods is unwise, but they will not fail from that, generally. And the radio is likely to see only limited usage once finished, my guess.

Terry

[John-Del]

On Thursday, June 29, 2017 at 4:27:12 PM UTC-4, Terry S wrote:
> What does the voltage drop to and settle in at? That's the real question.

It hits 470v about 3 seconds after turn on and about 5 seconds after that it settles down to 350v. Probably 5 seconds of being 20v above rated working voltage. If they are indeed under rated by 20%, it's running below that value at all times.

>And the radio is likely to see only limited usage once finished, my guess.
>
> Terry

It's not the hours Terry, it's the cold starts! :)

I thought I was finished with this but I totally forgot about the Mystery Box 'O Caps under the chassis. My first inclination was to leave them in there, but three of the sections have considerable voltage across them, so that's next.

If I have to order any caps for the MB'OC, I'll order some 500V electros for the hell of it. If not, I'll leave the 450v caps as is.

John
Wolcott, CT

[Peter Wieck]

On Friday, June 30, 2017 at 11:36:10 AM UTC-4, John-Del wrote:

> It hits 470v about 3 seconds after turn on and about 5 seconds after that it settles down to 350v.

OK.... I GOTTA ASK!!

Schematic here:

https://www.tubesandmore.com/sites/default/files/schematics/philco_radio_television_corp_60_pg4-3.png

Where are you measuring 470V? AC or DC?

Here is why:
a) The rectifier will not pass DC instantly. So, in theory, there should be 0 voltage on the filter caps until the rectifier starts to pass - and any that is on it will be AC.
b) If you are measuring at the transformer, the voltage will be high as the transformer is unloaded. As the transformer loads, voltage will drop. But the schematic calls for dramatically more voltage - see below.

Note that per the schematic, there is 680 ACV on the plate of the rectifier.
350 V on the output side, so you are dead-on. But I do not see a source for the 470 V

So, I am curious.

One more question: What was the OEM voltage on the 8 uF filter caps?

The cap values inside the 'black box' are:

A 0.09 uF
B 0.09 uF
C 0.05 uF
D 0.50 uF

Respectively.

The connections are so-labeled on the schematic.

[John-Del]

On Friday, June 30, 2017 at 12:58:24 PM UTC-4, Peter Wieck wrote:
> On Friday, June 30, 2017 at 11:36:10 AM UTC-4, John-Del wrote:
>
> > It hits 470v about 3 seconds after turn on and about 5 seconds after that it settles down to 350v.
>
> OK.... I GOTTA ASK!!
>

AND I'M COMPELLED TO ANSWER!!!

>
> Where are you measuring 470V? AC or DC?

DC, and right *across* the two 8uf caps. It probably would be higher with respect to chassis ground (tapped resistor on low side of caps to ground) but that wouldn't matter as far as the caps are concerned.

> a) The rectifier will not pass DC instantly. So, in theory, there should be 0 voltage on the filter caps until the rectifier starts to pass - and any that is on it will be AC.

This is the fastest tube rectifier I've ever seen. I'm not exaggerating when I say that it starts putting out considerable voltage three seconds after AC is applied. It reaches 470 within a couple of seconds of conduction and sits there for about 5 seconds until the rest of the tubes start conducting. I have normal sound in 15 seconds after turn on.

>
> Note that per the schematic, there is 680 ACV on the plate of the rectifier.
> 350 V on the output side, so you are dead-on. But I do not see a source for the 470 V

The 470 is the B+ voltage with no load.

>
> One more question: What was the OEM voltage on the 8 uF filter caps?

Fortunately, both wet electros are the originals and are marked 8uf 475 volts. Strangely (and unrelated to the subject), both are marked Philco but have two different part numbers on them despite having the same exact value, voltage rating, physical size and terminal arrangements.

The way the wet electros were built, I can see them taking considerable overvoltage without damage. The original capacitor contained a loosely wound well spaced rolled up coil of metal sitting in a borax bath. The spiral was attached to the positive lead and the and the can attached to the negative. Even if it did arc over, it seems that it would be very difficult for it to sustain any permanent harm, unless the electrolyte bath changes chemically during an arc overs.

> The cap values inside the 'black box' are:
>
> A 0.09 uF
> B 0.09 uF
> C 0.05 uF
> D 0.50 uF
>

Yep, that's what my schematic calls them out as. I know there are many iterations of this radio but so far, everything I've seen in my radio is exact to the schematic I have. Once I do that MB'OC, I'll call it done.

One more interesting item (again, unrelated to the subject). The original volume control was beyond salvage - it's carbon track abraded mostly away - and I had a donor fortunately. I took the donor apart to gently clean it and was surprised to see it didn't have the typical wiper rubbing along a carbon track, but a carbon track with a thin spring steel strip running it's entire length. The wiper rode on the spring steel pushing the spring steel strip *against* the carbon track along it's length as needed, but not actually wiping it. Brilliant. This control will surely last many times longer than a direct wiper/carbon track control.

Thanks for the help and advice guys.

John
Wolcott, CT

[John-Del]

The 60 ran fine for several days, then quit. Voltages around the 6A7 osc are way off. The oscillator coil checks fine resistance-wise and I swapped in another osc tube and still have the same issue.

Before I got into it further, I decided to finish the one item I hadn't taken care of; the large capacitor block. The schematic I have been using has been exact until I reached this one item. My schematic shows 4 cap sections (.05 .09 .09 .5 ), but my radio has five wires coming out of the block. The label on the block shows 30-4063.

I checked all sections and the four sections I know about read normal capacitance and some slight leakage. The fifth unidentified lead reads 100pf and no leakage. I was going to add the 100pf as my fifth capacitor and stuff it back together but I noticed in the revision notes of my schematic that the 30-4063 has a fifth section that wasn't used, and replaced by the four section block.

There are two things that don't add up. My radio uses the fifth section and it's wired directly across capacitor item 8. The other is that the revision notes say that the "unused" section is 0.2uf, quite a bit higher in value than the 100pf I'm reading. That section could be bad, but it's not shown even being used on the schematic anyway. Odd.

Internet links that supposedly have information on these blocks turn up a 404 dead end. Any insight appreciated.

John
Wolcott, CT

[Peter Wieck]

On Wednesday, July 5, 2017 at 2:06:25 PM UTC-4, John-Del wrote:

Please note the interpolations:

> The 60 ran fine for several days, then quit. Voltages around the 6A7 osc are way off. The oscillator coil checks fine resistance-wise and I swapped in another osc tube and still have the same issue.

"Quit": Stone-silent? Hiss? Mild hum? Something else?

> Before I got into it further, I decided to finish the one item I hadn't taken care of; the large capacitor block. The schematic I have been using has been exact until I reached this one item. My schematic shows 4 cap sections (.05 .09 .09 .5 ), but my radio has five wires coming out of the block. The label on the block shows 30-4063.
>
> I checked all sections and the four sections I know about read normal capacitance and some slight leakage. The fifth unidentified lead reads 100pf and no leakage. I was going to add the 100pf as my fifth capacitor and stuff it back together but I noticed in the revision notes of my schematic that the 30-4063 has a fifth section that wasn't used, and
replaced by the four section block.

100 pF.... that could be done with a couple of bits of foil - I expect that the 0.2 cap has crapped out and all you have left is the end-bits giving you the 100 pF. In this case, *DO* replace it with an 0.2 value cap. But? "Across cap #8? Radio side or ground side? See below.

Silly question: Is the cap box grounded via the case, or does it have a separate ground wire? If not, could the mysterious wire be the common ground? Which is now pretty obviously open?

> > There are two things that don't add up. My radio uses the fifth section and it's wired directly across capacitor item 8. The other is that the revision notes say that the "unused" section is 0.2uf, quite a bit higher in value than the 100pf I'm reading. That section could be bad, but it's not shown even being used on the schematic anyway. Odd.

Again, if the the fifth wire is the ground - that would explain all, as there is no specified connection point on the schematic. Just "ground".

And, do you have a tube tester such that you can verify that all the tubes are good otherwise? You might be surprised at how often these tube might fail after many years of not doing anything, adding to which we generally run at higher voltages today than once upon a time. Just some random thoughts.

You have done all the other caps?

[John-Del]

On Wednesday, July 5, 2017 at 4:32:21 PM UTC-4, Peter Wieck wrote:
> On Wednesday, July 5, 2017 at 2:06:25 PM UTC-4, John-Del wrote:
>
> Please note the interpolations:
>
> > The 60 ran fine for several days, then quit. Voltages around the 6A7 osc are way off. The oscillator coil checks fine resistance-wise and I swapped in another osc tube and still have the same issue.
>
> "Quit": Stone-silent? Hiss? Mild hum? Something else?
>

*Very* quiet. If you put your ear to the speaker you can hear just the bit of hiss from the audio section. If I put my finger on the grip cap of the AF tube, the hum is loud and clean. Any voltage checks from the volume control on out shows the AF section is fine.

> > Before I got into it further, I decided to finish the one item I hadn't taken care of; the large capacitor block. The schematic I have been using has been exact until I reached this one item. My schematic shows 4 cap sections (.05 .09 .09 .5 ), but my radio has five wires coming out of the block. The label on the block shows 30-4063.
> >
> > I checked all sections and the four sections I know about read normal capacitance and some slight leakage. The fifth unidentified lead reads 100pf and no leakage. I was going to add the 100pf as my fifth capacitor and stuff it back together but I noticed in the revision notes of my schematic that the 30-4063 has a fifth section that wasn't used, and
> replaced by the four section block.
>
> 100 pF.... that could be done with a couple of bits of foil - I expect that the 0.2 cap has crapped out and all you have left is the end-bits giving you the 100 pF. In this case, *DO* replace it with an 0.2 value cap. But? "Across cap #8? Radio side or ground side? See below.

Yes, connected to the high side of capacitor #8. #8 is the cathode bypass capacitor shared by the 6A7 and the 78 IF tubes in my version. Later versions split the cathodes up so they each have their own resistor and bypass cap. In my version, the fifth wire out of the filter box goes to the common cathode of the 6A7 and 78.

>
> Silly question: Is the cap box grounded via the case, or does it have a separate ground wire? If not, could the mysterious wire be the common ground? Which is now pretty obviously open?

When I removed the stuffin' out of the box, it had a single uninsulated wire coming out of the tar blob and soldered directly to the box. When checking the individual sections for value and leakage (post-mortem curiosity really), all the caps in the box read properly (other than some leakage) using the metal box as common ground for all, so they are clearly all tied together with a common ground which is the box itself. In any case, if the mystery wire was meant to be a common ground, then it was wired on the wrong side of capacitor #8.

Also, the revision notes at the bottom of my schematic describes the box as being a five section deal to be superseded by the later 4 cap version. I ended up rebuilding the box using the four known caps and simply added the 0.2 in parallel with #8 capacitor, and the radio remains silent (other than the aforementioned audio section which has plenty of zing).

> And, do you have a tube tester such that you can verify that all the tubes are good otherwise?

I have more testers than anyone should own. I will test the 6A7 when I get a chance to revisit Mister Sixty in the next couple of days, although I did try my back up 6A7 which I thought was good..

> You have done all the other caps?

Now that the mystery box is done, yes.

John
Wolcott, CT

[John-Del]

On Wednesday, July 5, 2017 at 2:06:25 PM UTC-4, John-Del wrote:

>

> The 60 ran fine for several days, then quit. Voltages around the 6A7 osc are way off. The oscillator coil checks fine resistance-wise and I swapped in another osc tube and still have the same issue.
>

I'm 100% sure the oscillator is not running and 98% sure the oscillator coil is causing it. The primary and secondary coils read OK with a resistance check, but I pulled the coil anyway and will rewind the top coil. I counted 18 turns when I unwound the primary, is this what most folks get? It also fell apart in several places during the unwind procedure. Right now the coil has been cleaned and dipped and when it dries, I'll add the outside winding and try again.

John
Wolcott, CT

[joybird]

If the Osc Coil checked good, why rewind it????

What are the B+ voltages ?

[joybird]

Why did you put a .02 across the 8 MFD Filter Cap ???? Does not belong there.
The Block you rebuilt had four caps and one common ground wire. NOT a .02 cap ??

[joybird]

On Thursday, July 6, 2017 at 4:35:42 PM UTC-4, joybird wrote:

OH I see you put it across #8 Cap. Remove it, not cap used with #8
THe change states the .02 cap not used only the 4 original values
Suggest you read schematic and make sure the 4 caps are going to the correct places. CAPS A B C D All shown as #20 on the schematic. NO other cap is required in that Block or the Replacement Block suggested.

[John-Del]

On Thursday, July 6, 2017 at 4:35:42 PM UTC-4, joybird wrote:

The oscillator isn't running with two different 6A7s which both previously worked in the radio. When I first got it up and running, it ran a few days and the antenna coil's primary side became intermittent and then finally died causing very poor sensitivity where before it was pulling in distant stations with a short wire. I rewound the antenna coil and it performed again like new - until this latest problem after another few days of burn in.

Research shows that these Philco 60s are notorious for issues on both the antenna and osc coils, so even if the osc coil was OK, at least I will have eliminated it as the problem now and as a problem in the future.

> What are the B+ voltages ?

Plate voltage of the 6A7 was high IIRC, but the screens were way down causing the resistors to run hot. Removing the 6A7 restored the voltages. The second 6A7 acted the same. All resistors are new and they remain on value.

>
>....

> OH I see you put it across #8 Cap. Remove it, not cap used with #8
> THe change states the .02 cap not used only the 4 original values
> Suggest you read schematic and make sure the 4 caps are going to the correct places. CAPS A B C D All shown as #20 on the schematic. NO other cap is required in that Block or the Replacement Block suggested.

This radio never had any work done with the filter block, so I'm confident that the wiring was original. My block has the five wires coming out of it with the part number 30-4063 printed on it's label, and which the notes describe as a five section block with the fifth section not used in *later* versions.

The first four sections of the filter block match the schematic I'm using exactly, except the fifth wire going to the high side of capacitor item #8.

In any case, adding or removing any capacitance to the 6A7 plate bypass did not have any affect on the oscillator, and it ran for several days with the original fifth wire installed.

[John-Del]

On Thursday, July 6, 2017 at 5:55:29 PM UTC-4, John-Del wrote:

>
> Research shows that these Philco 60s are notorious for issues on both the antenna and osc coils, so even if the osc coil was OK, at least I will have eliminated it as the problem now and as a problem in the future.
>

Oy.. forgot to add that before I started unwinding the primary side of the osc coil, I read leakage between the two windings. Unfortunately, I forgot to measure the inductance and rings of the coil before unwinding it.

[John-Del]

Question about the 100pf cap: is this "Micamold" capacitor stuffed in the coil (#13) a real mica? Some reading suggests that despite the name, some Micamolds are paper. I have a ceramic disc capacitor of 110pf I can install, but if this is a true mica and known to be reliable, I'm inclined to leave it in. If the consensus is replace it, that's what I'll do.

John
Wolcott, CT

[Peter Wieck]

John:

Micamold caps have an excellent reputation for reliability. But, as you suggest, they came in two flavors - mica and 'hermetically sealed' paper. In my history, I have found more than a few bad ones, but 100% of those had physical signs of damage. Cracks and such.

That being written, there is no reason *not* to replace it if it gives you additional peace-of-mind.

[John-Del]

Thanks again Peter. If you said they *never* go, I'd reinstall it. But I'll replace the cap for that old piece of mind. Perhaps tomorrow I'll get the chance to wind the outer coil and try it.

John
Wolcott, CT

[Foxs Mercantile]

On 7/7/2017 5:22 PM, John-Del wrote:
> Thanks again Peter. If you said they*never* go, I'd reinstall

> it. But I'll replace the cap for that old piece of mind.

Micamold was a brand name. They made two types of capacitors.
The familiar postage stamp types that were indeed mica dielectric,
and the larger ones, there were paper dielectric.

Round about 1000 pF was the demarcation point. 1000 pF and less
were mica, Values over 1000 pF (0.001 uF) were paper and should
always be replaced.

[John-Del]

On Thursday, July 6, 2017 at 4:46:39 PM UTC-4, joybird wrote:

> The Block you rebuilt had four caps and one common ground wire. NOT a .02 cap ??

I finally found a schematic for my version and it confirms what I found. This schematic shows a five way filter block with the 0.2 *and* it it's wired across capacitor #8 in the 6A7 plate circuit, exactly how mine is wired. It also has no actual ground wire, just uses the case as the common ground. I believe the five way block started with run number 3. I can't believe how many revisions Philco made without differentiating the model code inside.

Here's the schematic: http://imgur.com/a/vwW9b


John
Wolcott, CT

[John-Del]

Okay, this thing kicked my ass, ate my lunch and I'm pretty sure it grabbed some beer while I was still on the floor.

I can't get the 6A7 to oscillate. All caps are new, most resistors are new and those that aren't are very close in value. The radio worked almost a week perfectly after the work was done, then failed to start one morning. It was not intermittent or quirky, it ran perfectly with surprising sensitivity on a short wire.

Plate voltage is fine. G2 dropped from 270 to 98 and the feed resistors are hot. G3/5 dropped from 75 to 58. G1 went from -20 to +2.5. Cathode at 3V. Voltages return to normal/high with the tube out except of course for G1.

Because my antenna coil failed after the first 15 hours and had to be rewound, I pulled the osc coil and found a lot of green under the exterior winding, so I removed it, cleaned it up, and rewound the outer winding figuring that even if it wasn't the problem, it would be in the future. Same problem. I found a donor coil in excellent shape (looks like it was replaced at one point), and still nothing. Both my rewound coil and the replacement check fine resistance wise, and both read the same inductance on each winding. The replacement coil rings a bit better.

The tuner gangs are not touching, and the padding capacitors are not shorted or leaking. I moved them through their range but nothing. I disconnected the band switch from the osc coil and tried two different 110pf caps (reinstalled the original mica that reads 120pf with zero leakage).

I have an extra 6A7 and I'm *pretty* sure the extra 6A7 from the donor carcass worked while I was rotating tubes, but I can't be 100% sure. What I do know is that both tubes act exactly the same way in the circuit. I've also read internet mumbling about this tube being problematic at this age (dying without warning).

I'm missing something here but I can't put my finger on it. My wife insists it's haunted but I can't see it being anything at this point other than both 6A7 converters being flaky.

This is a closer schematic to what I posted above, and it might be exact:

http://imgur.com/a/fDtx2

John
Wolcott, CT

[Peter Wieck]

Various blind shots-in-the-dark:

Is the tuning cap isolated from the chassis? Sometimes the rubber grommets fail. This can be a *REAL* issue.

Along these lines, are the brass-wipers clean and connecting.

Are there any pin shorts? Look under the chassis for wires shorting or insulation missing at critical points. One of my 'shots' is that something is draining B+ and acting as a resistor when it should not - or a short. That could also be any of several tubes.

Just for giggles - with the tubes *OUT*, test for extraneous shorts at the tube pins.

As I remember, the 6A7 is a 7-pin pre-octal. I have a couple that I can run past the big Hickok and verify 'goodness'. I would be glad to send one along gratis, if needed. Or, if you give me a list, I will gather what I have along those lines.

[John-Del]

On Thursday, July 13, 2017 at 12:51:58 PM UTC-4, Peter Wieck wrote:
> Various blind shots-in-the-dark:
>
> Is the tuning cap isolated from the chassis? Sometimes the rubber grommets fail. This can be a *REAL* issue.
>

The grommets are in good shape, and the tuner is actually electrically grounded with a hard wire anyway.

> Are there any pin shorts? Look under the chassis for wires shorting or insulation missing at critical points. One of my 'shots' is that something is draining B+ and acting as a resistor when it should not - or a short. That could also be any of several tubes.

No shorts, no bare wires. A lot of guys bitch about the bakelite caps, but these free up a TON of room underneath.

The rest of the tubes show normal voltage, and indeed, I can pass an IF signal through it. Audio section is loud and clear. When the 6A7 is removed, all the voltages rise to normal or above except for the G1 which would ordinarily be negative with the osc running properly.

> As I remember, the 6A7 is a 7-pin pre-octal. I have a couple that I can run past the big Hickok and verify 'goodness'. I would be glad to send one along gratis, if needed. Or, if you give me a list, I will gather what I have along those lines.

Thanks for the offer Peter. I went through my thousands of tubes last night squirreled away in my basement and couldn't find one. I may still have one somewhere. The dig though did turn up some radios I didn't even know I had, a Precision E-400 generator I didn't know I owned and lots of NOS tubes. I have at least two dozen brand new Raytheon 42s. I really need to catalogue what I have.

If I run into a dead end any decide to try another converter, perhaps we can work out a swap.


John
Wolcott, CT

[John-Del]

I found an unidentified (and very compact) 30's AM/SW chassis in my boneyard, and it has a 6A7. I tried that in the Philco and it still doesn't work. The unidentified radio is complete but has one broken tube, a 43. I'm going to see if I have one of those and then power it up to check the 6A7s in a working radio. BTW, this compact unidentified radio has a factory installed three wire AC cord. I've never seen this before. There's no plug on the end so I don't know how it was terminated. Since there were no three pronged outlets back then I'd guess two of the wires for AC and the third a ground wire. This little radio also has a bottom belly pan with a stamped out area about 2" by 2" that has an asbestos sheet riveted over the hole. Interesting little guy and seems well made.

John
Wolcott, CT

[C.Copperpot]

On Thu, 6 Jul 2017 15:16:57 -0700 (PDT), John-Del <ohg...@gmail.com>
wrote:

>On Thursday, July 6, 2017 at 5:55:29 PM UTC-4, John-Del wrote:
>
>>
>> Research shows that these Philco 60s are notorious for issues on both the antenna and osc coils, so even if the osc coil was OK, at least I will have eliminated it as the problem now and as a problem in the future.
>>
>
>Oy.. forgot to add that before I started unwinding the primary side of the osc coil, I read leakage between the two windings. Unfortunately, I forgot to measure the inductance and rings of the coil before unwinding it.

My Philco 60 does about the same thing. Played great for a few hours,
then I heard a pop sound in the speaker - then no reception. I can get
it to come back if I set my signal generator to the i.f. and touch it
a few times on the 6A7 grid cap. Looking at the coils, I remember one
had a winding inside the tube that was hard to see. The wiring was all
dark and green. I figured that was the problem and shelved the unit
(about 10 years ago). I'll get back to it someday - maybe.

[John-Del]

On Thursday, July 13, 2017 at 6:50:01 PM UTC-4, John-Del wrote:
>>BTW, this compact unidentified radio has a factory installed three wire AC cord. I've never seen this before. There's no plug on the end so I don't know how it was terminated. <<

OK, I feel like a total jackass.

In all my years, I've never once ran across a resistance AC cord.

Ever.

Yes, I've heard about them and just assumed they were two wires with the resistance wire used for both conductors. Color me ignorant. So, a little web searching later and I've replaced the resistance wire section with 8uf worth of mylar capacitors and I'm running just under each tube's filament (I may tweak it up later if I restore it - it's sans cabinet).

Anyway, the little unidentified AC/DC AM/SW radio works albeit weakly on AM, but more importantly the 6A7 oscillator stays running through the whole range on both AM and SW bands, and does so on all three of my 6A7 tubes, so I'm back to square one with the Philco 60.

John
Wolcott, CT

[Peter Wieck]

There are two schools on the RLC - I choose installing MOAR aluminum-finned power resistors to caps - 28 flavors of ice-cream and all that.

So - what can drain B+ off when the 6A7 is in place:

antenna coil?
First IF can?
Bad resistor?
Cap pretending to be a resistor under load?
Short between sections in tuning cap?

It will be something that is operational *ONLY* when the 6A7 is conducting...

[John-Del]

On Friday, July 14, 2017 at 2:51:02 PM UTC-4, Peter Wieck wrote:
> There are two schools on the RLC - I choose installing MOAR aluminum-finned power resistors to caps - 28 flavors of ice-cream and all that.
>

There's no room. This is a very tight layout. The footprint is 4" X 10" by eyeball. I'll post a picture of the chassis when I can. I can't see it dissipating that much heat without destroying the cabinet. OTOH, since it has no cabinet...

> So - what can drain B+ off when the 6A7 is in place:
>
> antenna coil?
> First IF can?
> Bad resistor?
> Cap pretending to be a resistor under load?
> Short between sections in tuning cap?
>
> It will be something that is operational *ONLY* when the 6A7 is conducting...
>
> Peter Wieck
> Melrose Park, PA

I've checked all of those things. All caps are new and have been rechecked for value and leakage. Most resistors were out of tolerance and replaced, and those have been rechecked for value. My best guess right now is that the original osc did fail and I somehow miswired it when I reinstalled both the rewound coil and subsequently it's replacement. I did a quick review by schematic and I was pretty sure right now, but since none of this makes sense, I can't think of anything else unless my donor coil, despite reading proper resistance, is also bad! I'm going to redraw the osc coil terminal out and check my wiring one more time.

Last plan is to disconnect the antenna input side from the tube to see if it will oscillate.

John
Wolcott, CT

[John-Del]

Okay, I'm at a dead end here. I've redrawn the oscillator coil diagram and confirmed that I wired the coil in correctly. I've reconfirmed that both my rewound osc coil and my donor coil are reading normal continuity on both windings and have no leakage between them. Every resistor, capacitor, and padder are right where they need to be in the oscillator circuit. The 6A7 socket is clean, tight, and I read no leakage between the pins. Counting the tube socket and tuner, there are 11 parts in the local oscillator, and it's defying all my attempt to make it run. Amazing.

I removed the gang tuner and checked the padder caps/micas on both sections, and they're fine. The tuner swings 25 to 500 pf on both the osc and rf sections opened to closed (sections look physically identical and read the same). I ran 600 volts across it looking for any leakage or arcing, and there's none. I cleaned it up a bit for aesthetic reasons, readjusted the back screw to better center the vanes, tested it once more for value and leakage, and will reinstall it next week. Even the gum rubber washers are perfect.

I've now tried 4 6A7s and none work. Coming full circle, I'm back at the oscillator coil. These coils are some 80 years old - any chance they've trapped some moisture? Anyone baked the crap out of these to solve a stubborn oscillator issue? The top lead of the coil is running between the coil form and the can. Is this right or should the top coil lead run down *through* the coil form, or does it not matter. Any chance playing with the cathode resistor value can help?

I'm going to try giving the coil a couple of days in a hot box and see what happens, but my next plan is to either replace the oscillator coil with a universal or change the converter tube to a later type. For the former, does someone make a universal coil that will fit the 60 directly without changing other parts?

Thanks for reading through all of this!

John
Wolcott, CT

[Jim Mueller]

On Fri, 07 Jul 2017 17:54:26 -0500, Foxs Mercantile wrote:

> On 7/7/2017 5:22 PM, John-Del wrote:
>> Thanks again Peter. If you said they*never* go, I'd reinstall it.
>> But I'll replace the cap for that old piece of mind.
>
> Micamold was a brand name. They made two types of capacitors.
> The familiar postage stamp types that were indeed mica dielectric,
> and the larger ones, there were paper dielectric.
>
> Round about 1000 pF was the demarcation point. 1000 pF and less were
> mica, Values over 1000 pF (0.001 uF) were paper and should always be
> replaced.

Micamold also made resistors; they look like molded mica capacitors
except that they are about twice as long as they are wide and are marked
with three color dots.

--
Jim Mueller wron...@nospam.com

To get my real email address, replace wrongname with eggmen.
Then replace nospam with expressmail. Lastly, replace com with dk.

[Jim Mueller]

On Fri, 30 Jun 2017 11:00:48 -0700, John-Del wrote:

> On Friday, June 30, 2017 at 12:58:24 PM UTC-4, Peter Wieck wrote:
>> On Friday, June 30, 2017 at 11:36:10 AM UTC-4, John-Del wrote:
>>
>> > It hits 470v about 3 seconds after turn on and about 5 seconds after
>> > that it settles down to 350v.
>>

>> snip

> John Wolcott, CT

Check the manufacturer's data sheet for the capacitors you used. Many,
but not all, modern capacitors have a surge voltage rating with a time
limit, usually 30 seconds. You will have to go the the manufacturer's
web site and look up the part number of your capacitors to get this
information; it won't be in distributor (Digi-Key, Mouser, etc.) catalogs.

You might be fine with what you have.

[Jim Mueller]

Just for giggles and since you have a quick heating rectifier, how about
measuring the voltages on the 6A7 after the rectifier heats but before
the other tubes do? This would tell us if the problem is something to do
with the tube being physically in place (like a short that only happens
when the tube in) or if it requires the tube to be operating.

When you wired the oscillator coils, did you get the polarity correct?
The coils have to be phased correctly or the oscillator won't work. This
won't explain the initial failure but could be an issue with later work.

[Jim Mueller]

On Thu, 06 Jul 2017 14:06:21 -0700, joybird wrote:

> On Thursday, July 6, 2017 at 4:35:42 PM UTC-4, joybird wrote:
>>

snip

>
> OH I see you put it across #8 Cap. Remove it, not cap used with #8 THe
> change states the .02 cap not used only the 4 original values Suggest
> you read schematic and make sure the 4 caps are going to the correct
> places. CAPS A B C D All shown as #20 on the schematic. NO other cap is
> required in that Block or the Replacement Block suggested.

The second schematic he posted shows a 5 section capacitor connected as
he described.

[John-Del]

Oooooh, interesting thought. I have had my clipped in circuit as I've powered up the radio several times, and the grid voltages start high and drop as the 6A7 tube warms. I can try interrupting the filament to the tube and see if the voltages rise as the tube cools, which I'd bet almost anything will be the case. I can also try delaying the B+ until the tubes are warm.

> When you wired the oscillator coils, did you get the polarity correct?
> The coils have to be phased correctly or the oscillator won't work. This
> won't explain the initial failure but could be an issue with later work.
>
> --
> Jim Mueller wron...@nospam.com

If you mean wired as in the sense of installing the coil in the chassis, I'm pretty sure I did. I retraced the schematic several times. I also tried reversing the outer coil's polarity and nothing changed. I have not tried reversing the polarity on the G1 side.

If you mean when I rewound the feedback side, I do believe it's wound in the correct direction (CCW looking at it from the connection end). My donor coil is wound in the same direction and from all tests, seems like it's in good shape.

Giving this some thought last night, my next plan is to simply reinstall the tuner and, while the radio is running, run a heat gun into the osc coil and watch the G1 on the scope to see if it starts oscillating.

Thanks for the time to read all of this and the advice everyone.

John
Wolcott, CT

[Jim Mueller]

On Sun, 16 Jul 2017 05:09:22 -0700, John-Del wrote:

> On Sunday, July 16, 2017 at 2:36:17 AM UTC-4, Jim Mueller wrote:

snip

>>
>> Just for giggles and since you have a quick heating rectifier, how
>> about measuring the voltages on the 6A7 after the rectifier heats but
>> before the other tubes do? This would tell us if the problem is
>> something to do with the tube being physically in place (like a short
>> that only happens when the tube in) or if it requires the tube to be
>> operating.
>>
>>
> Oooooh, interesting thought. I have had my clipped in circuit as I've
> powered up the radio several times, and the grid voltages start high and
> drop as the 6A7 tube warms. I can try interrupting the filament to the
> tube and see if the voltages rise as the tube cools, which I'd bet
> almost anything will be the case. I can also try delaying the B+ until
> the tubes are warm.

Since the 6A7 isn't oscillating, it draws more current. This could be
the cause of the reduced voltages. Or maybe not.

>
>
>> When you wired the oscillator coils, did you get the polarity correct?
>> The coils have to be phased correctly or the oscillator won't work.
>> This won't explain the initial failure but could be an issue with later
>> work.
>>
>> --
>> Jim Mueller wron...@nospam.com
>
> If you mean wired as in the sense of installing the coil in the chassis,
> I'm pretty sure I did. I retraced the schematic several times. I also
> tried reversing the outer coil's polarity and nothing changed. I have
> not tried reversing the polarity on the G1 side.

Reversing one coil is enough.

>
> If you mean when I rewound the feedback side, I do believe it's wound in
> the correct direction (CCW looking at it from the connection end). My
> donor coil is wound in the same direction and from all tests, seems like
> it's in good shape.

Reversing the connections takes care of the possibility of it being wound
in the wrong direction

>
> Giving this some thought last night, my next plan is to simply reinstall
> the tuner and, while the radio is running, run a heat gun into the osc
> coil and watch the G1 on the scope to see if it starts oscillating.

Is the scope connected through a X10 or X100 probe? A direct connection
(X1) is likely to load the oscillator so much that it won't oscillate.
You could also try putting the scope probe near some of the oscillator
wiring without actually physically connecting it. You might be able to
pick up enough signal that way while minimizing loading.

>
> Thanks for the time to read all of this and the advice everyone.
>
> John Wolcott, CT

You're welcome.

[John-Del]

On Sunday, July 16, 2017 at 11:22:31 PM UTC-4, Jim Mueller wrote:

>
> Is the scope connected through a X10 or X100 probe? A direct connection
> (X1) is likely to load the oscillator so much that it won't oscillate.
> You could also try putting the scope probe near some of the oscillator
> wiring without actually physically connecting it. You might be able to
> pick up enough signal that way while minimizing loading.

10X probe. FWIW, when I was experimenting with another working radio that uses the same 6A7, I was able to see the osc on the G1 at 10X and even direct. Admittedly, the circuit topography is different between the two radios but I was able to see the osc signal at the 6A7 grid cap (antenna side) at a reduced amplitude, and if I grounded the G4 grid cap, the G1 waveform was still rock solid, so I don't think scope loading at the G4 grid cap at least will stop the oscillator.


Today when I get to work I'll reinstall the tuner and try heating the coil. Details later...

John
Wolcott, CT

[John-Del]

Fixed. Where do I pick up the idiot of the month award?

Figuring it was either some sort of wonky oscillator coil or something I did wrong, I re-re-re-rechecked my work. I did indeed put the oscillator coil in properly, so I turned to the only other work done after the oscillator quit which was rebuilding the metal can filter box, so I checked that again.

It turns out that I put the A section of filter box to the G2 of the 6A7 oscillator where it didn't belong, effectively putting a big virtual thumb on the oscillator. I removed it and put it on the G3/5 grid where it belongs, and the oscillator is back, and so is the radio.

So - the original problem with the oscillator quitting was the oscillator coil, despite the fact that it read proper resistance. Both my rewound coil and the donor coil work properly.

So the summery is:

1) radio worked well at least 5 days after an *almost* complete recap and resistor check/replace and alignment.

2) radio lost sensitivity, just the locals came in. Found the outer winding of the antenna coil open. Rewound outer coil and radio returned to good distance operation.

3)radio ran well another week and went silent except for some small hum and hiss at speaker. Found oscillator not running and suspected osc coil outer winding after trying a working 6A7 osc tube. Before pulling coil, rebuilt the filter box as they were the last caps not replaced. No change, osc not running.

4) rewound outer winding of oscillator coil, still no change - osc still not running. Installed donor coil, osc still not running.

5) found miswired section A of restuffed filter box inadvertently put on G1 of oscillator tube (pin 4). Replaced wire to G3 (pin 3), operation returned. Installed original but now rewound osc coil.


Info that might help someone in the future: The oscillator coil reads 19uh on the feedback winding and 191uh on the G1-Plate side. If you use a ringer, the feedback coil rings 10 and the G1-Plate side rings 55.

The oscillator will run even with the 110 pf mica removed between the osc coil windings.

The oscillator will run even with the scope directly on the G1 with a 10X probe and show a nice clean sine wave of just under 100Vp-p. The oscillator signal can also be seen on the grid cap of the 6A7 as a quick test if you're checking from the top of the chassis, although the wave shape is distorted and changes *shape* with tuner position.

Thanks for all the time and advice.

John
Wolcott, CT

[Michael A. Terrell]

Peter Wieck wrote:
>
> Note that per the schematic, there is 680 ACV on the plate of the rectifier.
> 350 V on the output side, so you are dead-on. But I do not see a source for the 470 V


340VAC*1.414 (Peak voltage)=480.76 VDC, with no load. Subtract the
forward drop for the tube rectifier, and you'll see the 470VDC


--
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

[Peter Wieck]

Nothing "idiotic" here. Just pretty normal hobby behavior. We get short bursts at our hobby, which involves pretty complex and detailed operations. That a connection gets missed or mis-made is no cause for shame, especially as you caught it before any damage was done *AND* rewound a coil in the process!

I could tell you about staring at a silent Zenith 600-series T/O for some hours - before realizing that the headphone jack needed to be connected before the speaker would work. Or the time that I pinched a wire on a chassis - fine with the top off... not so much with the top on. Off/On... repeat.

Enjoy the positive results!

[Terry S]

And I could relate a story about a small Panasonic table top transistor radio that worked fine as long as the volume knob was installed.

Dead silent with the knob removed.

Terry

[John-Del]

On Tuesday, July 18, 2017 at 10:53:01 AM UTC-4, Peter Wieck wrote:
> Nothing "idiotic" here. Just pretty normal hobby behavior.

You're being generous, but I thank you just the same.

When you think about it, there wasn't much I could have done to intentionally bug the radio that would duplicate exactly the exact symptoms I had! The osc wasn't running with the bad coil, but inadvertently adding some capacitance to the grid duplicated the symptom exactly , right down to duplicating the same incorrect voltage readings!

Props for a particularly effective self-sabotage, no?

What I should have done was repair the osc first, then rebuilt the filter block which I knew was OK and not causing the oscillator problem. If the osc quit right after I reinstalled the filter block, that's the first place I would have checked.


>
> Enjoy the positive results!
>


Thanks. It's a strong player. Locals crisp and clear, and the distant stations (sport radio, NY) and oldies (MA) come in strong and clear with about 6' of wire here in central CT, as good as any modern radio I have. I also discovered there's some benefit to the "police" band. The low side of the police band starts at the high end of the AM band, and since there's a 24 hour computer generated traffic report that broadcasts on 1670, well beyond the radio's normal AM range, I can listen to that as well.

Thanks again for the offer of the 6A7 to try. I now have four that all work, so I should be good for a while anyway. Thanks to everyone else who helped.

John
Wolcott, CT