Chroma w/out luminance on CTC-11 roundie?
Phil Nelson
so I'll post here as Bill requested.
I picked up a second CTC-11 color roundie on craigslist for $1 (
http://antiqueradio.org/art/temp/FirstLook01.jpg ) and have just begun
working on it.
Lots of circuits are OK, but the picture is very dim. The first pic is the
dollar TV. The second is my restored CTC-11 showing the same thing.
http://antiqueradio.org/art/temp/BadPic.jpg
http://antiqueradio.org/art/temp/GoodPic.jpg
The color controls have an effect, but the contrast & brightness controls do
nothing. Bill suggested that I have chroma, but virtually no luminance, so I
am investigating the video amp/output board for starters. Here's that part
of the schematic, in two pieces.
http://antiqueradio.org/art/temp/VidBoardSchem1.jpg
http://antiqueradio.org/art/temp/VidBoardSchem2.jpg
The problem appears to be on this chassis, not the CRT. The CRT tests with
emission on all three guns, and I get the same bad picture when I plug this
chassis into the restored convergence assembly & CRT from my good TV.
Subbing known good tubes on the video board made no improvement. These are
video amp, 6AW8A, and video output, 12BY7A.
Voltage checks show excessive voltage on pin 8 of 6AW8A: 232 volts rather
than 120 as specified. The resistance on that pin is 49K rather than 150K as
specified. I replaced C5, the little electrolytic near the tube. Resistors
R48, R49, and R50 check out OK.
I'll continue checking resistors and the controls in these circuits unless
someone has a better idea. C2D is part of a four-section electrolytic can,
which I'll replace eventually. Two of the other sections are in the power
supply, and a third is in the AGC circuit. Three of the four sections seem
to be OK, so I don't know why this one in particular would be bad, but there
are lots of things I don't know.
All ideas are welcome, as usual!
Phil Nelson
vtc
If you have chroma without luminance you might want to check the video
delay line. Hard to tell from the jpg if you're missing video. Did you
check the HV on the CRT? A bad regulator or rectifier pulling that way
low could also cause a very dark picture.
jughead
Could you post the part of the schematic showing the
territory 'tween the 12BY7 and the CRT? I don't recomember if the
CTC-11 had a service switch or not.
oc
Bill Cohn
The brightness control is controlling the grid bias on the 12BY7A the
which is DC coupled to the CRT cathodes. The overall DC level on the
plate of the 12BY7A video output should change with the brightness
control. This would be best observed with a DC coupled oscilloscope but
can be monitored with a voltmeter though you are blind to the AC
component of the video signal. The Luminance signal is amplified by the
12BY7A and sent to the CRT cathodes and the chroma signal is mixed in at
the CRT grids. For everything to work properly the screen controls must
not be set to high or the CRT cutoff will be wrong.
Nice score for a buck though.
Regards,
Bill Cohn
Phil Nelson
I see the delay line -- cigar shaped tube behind the video board. I looked
it up in a solid-state TV book. They do describe the phenomenon of color
without b/w when the delay line is open.
I see three leads, two at one end and a single lead at the other. One of the
pair of leads goes to ground. I test 128 ohms between the non-ground lead on
that end and the single lead at the far end . . . .
Phil
Phil Nelson
> territory 'tween the 12BY7 and the CRT? I don't recomember if the
> CTC-11 had a service switch or not.
Here ya go.
http://antiqueradio.org/art/temp/VideoOutSchem.jpg
It does have a service switch. I used it on my restored set when adjusting
gray scale. Collapsed the display to a horizontal line.
Phil
jughead
>
> It does have a service switch. I used it on my restored set when adjusting
> gray scale. Collapsed the display to a horizontal line.
>
the 'service' position, check to be sure it's making proper contact
when in the 'normal' position.
oc
vtc
Best way to tell is to hang an oscilloscope on the input of the delay
line & look for video & then check the output of the delay line. That
will help to diagnose which direction to take.
Phil Nelson
> switch kills luminance when in the 'service'
> position, check to be sure it's making proper
> contact when in the 'normal' position.
What can I say -- Bill rules.
http://antiqueradio.org/art/temp/Napoleon1.jpg
http://antiqueradio.org/art/temp/Napoleon2.jpg
Amazing what a little spritz of DeOxit can do. Next time I find a CTC-11 in
a garage, I will not leave out that switch when cleaning the usual suspects!
Thanks.
Phil Nelson
jughead
AudioKarma thread before AudioKarma went bellyup, the original symptom
looked *exactly* like a heater-cathode short in the CRT. I.e., loss of
the luminance (video) signal while chroma remains normal. H-K shorts
were/are very common in the old jugs. If it's suspected, tapping on
the neck will usually cause the video to flash in and out. Just
sumpin' to remember if you continue working on these old beasties..
it's not if but `when` you'll run into a jug with H-K short.
Bill(oc)
Brenda Ann
"Phil Nelson" <philn...@nospam.xyz> wrote in message
news:mfGdnRcOm7UhFjTX...@giganews.com...
Wow... looks almost as bright as new. Just a little convergence touch up and
you should have a nice set there.
I finally got my old Crosley roundie (12") B/W sets in. Now I have to finish
cleaning up my new shop (was forced to move out of my 3m x 6m connex) so I
can work on them. (well, that and find the schematics that I have around
here somewhere...)
Phil Nelson
> a little convergence touch up and you should have a nice set there.
Fortunately, convergence is something I *can* do now, after spending hours
fussing & cussing over the other set.
This picture looks even better when I'm not using the cheapo DVD player in
my shop, which spews out RFI and makes herringbone interference.
The CRT is so bright, I wonder if it is the one installed in February '67
according to the warranty card. Or I suppose they could have replaced that
one at some point. The card has a CRT serial number, but I don't see
anything obvious on the tube. Maybe the serial number is scribed in the
glass somewhere obscure, or there was a sticker that fell off. If it's the
one from '67, they must not have played the TV very much.
Phil
jughead
>
> The CRT is so bright, I wonder if it is the one installed in February '67
> according to the warranty card. Or I suppose they could have replaced that
> one at some point.
>
'67 or so, roundies were well into obsolescence as rectangulars took
over the market.
>
> If it's the
> one from '67, they must not have played the TV very much.
>
oc
Brenda Ann
"jughead" <oldco...@gmail.com> wrote in message
news:20557ca2-a9f2-4c9a...@e4g2000prn.googlegroups.com...
On Sep 10, 8:59 pm, "Phil Nelson" <philnel...@nospam.xyz> wrote:
>
> The CRT is so bright, I wonder if it is the one installed in February '67
> according to the warranty card. Or I suppose they could have replaced that
> one at some point.
>
I seriously doubt if the set ever saw a second CRT replacement. Past
'67 or so, roundies were well into obsolescence as rectangulars took
over the market.
>
I replaced roundies up to at least 1974. Some customers just didn't want to
get rid of their "old reliable".
One thing that DID tend to irk me, though, was when a customer swore up and
down that they never had ghosting before I changed out their CRT... they
did, of course, but the picture was so dim that they couldn't see them if
they had to..
John Stone
TIydnfgNbZPQ1zfX...@giganews.com, "Brenda Ann"
<newsg...@fullspectrumradio.org> wrote:
>
> "jughead" <oldco...@gmail.com> wrote in message
> news:20557ca2-a9f2-4c9a...@e4g2000prn.googlegroups.com...
> On Sep 10, 8:59 pm, "Phil Nelson" <philnel...@nospam.xyz> wrote:
>>
>> The CRT is so bright, I wonder if it is the one installed in February '67
>> according to the warranty card. Or I suppose they could have replaced that
>> one at some point.
>>
> I seriously doubt if the set ever saw a second CRT replacement. Past
> '67 or so, roundies were well into obsolescence as rectangulars took
> over the market.
>>
>
> I replaced roundies up to at least 1974. Some customers just didn't want to
> get rid of their "old reliable".
>
"Old reliable" ?? Using the term "reliable" when discussing vacuum tube
based color tv's is a contradiction in terms.
jughead
>
> "Old reliable" ?? Using the term "reliable" when discussing vacuum tube
> based color tv's is a contradiction in terms.
>
considered a goodly lifespan for a set in daily use.
oc
Phil Nelson
> based color tv's is a contradiction in terms.
They have an awful lot of parts and pieces. It's kind of a miracle that a
60-year old color TV can be made to play at all.
Still, I was a bit surprised at how little it took to make this one go.
After replacing the burned thermistor, the most urgent chores were cleaning
controls and fixing the broken horizontal hold control.
All of the pots were DIRTY. Some barely moved at all, but they cleared up
and now move smoothly. If I had cleaned the service switch at that time, I
wouldn't have gone on a wild goose chase trying to solve the brightness
issue.
Replacing two weak tubes probably made it play better, but it might have
worked after a fashion with them in place.
It wouldn't have displayed a picture at all with a broken horizontal
control. It was bashed during a move, snapping the plastic shaft, pushing
the coil back off the subchassis, and bending the brass stem that holds the
moving core. I was able to straighten the threaded stem enough to get it
back into the coil form and lock the horizontal, but this won't be a
permanent solution until I can straighten it completely. Not sure whether
that can be done without breaking the core off the stem. Oh, for the old
days when you could just pull a new control from a bin and bill the customer
$1.25 for the part!
So, if you discount the horizontal control that broke in an accident, the
"make it go" work was replacing one burned part, shooting some cleaner
inside things, and replacing a couple of weak tubes. I suppose that might
have been a quick service call back in the day.
I hope something can be done with this awful tuner. I carefully put some
DeOxit on the wafer contacts, but it still barely tunes in anything unless
you stick it between two channels. Maybe I can reach in with a little piece
of pencil eraser held in long tweezers and polish away. But there are places
you just can't reach.
I got an "RCA Color TV Service Manual" from the library, and it briefly
mentions tuner cleaning. The factory recommended Clorathene NU (?) as a
cleaner, with a little bristle brush. Other cleaners may damage plastic
parts, it warns. I gather this kind of cleaning would have been done with
the tuner completely disassembled on the bench. Do not move the shaft while
cleaning, it warns, as dry contacts may be permanently scored and damaged.
I probably did everything wrong by shooting DeOxit and twirling the tuner
for 60 seconds. Oh well, I keep telling myself -- the TV only cost a dollar!
If all else fails, I can just duct-tape the channel selector to permanently
receive Channel 4 and pretend that the rest works :-)
Phil
Michael A. Terrell
Phil Nelson wrote:
>
> I hope something can be done with this awful tuner. I carefully put some
> DeOxit on the wafer contacts, but it still barely tunes in anything unless
> you stick it between two channels. Maybe I can reach in with a little piece
> of pencil eraser held in long tweezers and polish away. But there are places
> you just can't reach.
You might as well use a Dremmel tool with a grindstone. Both will
strip any remaining precious metal plating from the contacts.
--
You can't have a sense of humor, if you have no sense!
Richard Knoppow
Congratulations on getting this thing going:-)
The cleaner was probably some form of
trichloroethylene. This was widely available for cleaning
all sorts of stuff but is an environmental polutant so its
impossible to buy it now. I doubt if the De-Oxit damaged
anything. Tuner Lube, which is still available, was meant
for this job. It sounds more like the turret in the tuner is
not ligning up right than being dirty. If its off there is
likely an adjustment for it. I am assuming this set has the
very common Sarkes-Tarzian turret tuner but, if its old
enough, it may have something else.
--
Richard Knoppow
Los Angeles
WB6KBL
dick...@ix.netcom.com
Phil Nelson
Wafer tuners were also used in my cheapest b/w sets from the 1940s.
http://antiqueradio.org/art/temp/DirtyTuner.jpg
Someone thoughtfully discarded the shields, so it got plenty dirty.
Here's the tuner in my TV field strength meter. It makes the RCA tuner look
like a cheap toy. I gather this is a turret type.
http://antiqueradio.org/art/temp/FieldStrengthMeterTuner.jpg
I'm taking that as a No from Michael on polishing with a pencil eraser :-)
Among other warnings, the service book says that spray can change the value
of the neutralizing capacitor associated with the Nuvistor in the RF
section. Based on the symptom they describe, I seriously doubt this has
happened. But they go on to say that spray is NOT recommended for these
tuners, period.
In the factory, I suppose they would have torn apart the tuner for a full
rebuild followed by a realignment, or just thrown it in the garbage and
installed a new one. Neither one of those things is gonna happen here.
Not sure where to go with this. The tuner's pretty hopeless in this
condition, and the one in my other CTC-11 is almost as bad.
Phil Nelson
jughead
for a rebuild. A bit of Googling around finds this resource under 'TV
tuner rebuilders'-
http://www.superpages.com/yellowpages/C-Television+Tuner+Repair+&+Rebuilding/
Dunno what their rates would be in this day and age, though.
oc
Jeffrey D Angus
> http://antiqueradio.org/art/temp/DirtyTuner.jpg
Ewwwww, i always wondered how accurately they aligned those
with marginal test equipment at the time.
> I gather this is a turret type.
>
> http://antiqueradio.org/art/temp/FieldStrengthMeterTuner.jpg
Yes a truly inspired design.
Jeff
--
�Egotism is the anesthetic that dulls the pain of stupidity.�
Frank Leahy, Head coach, Notre Dame 1941-1954
Richard Knoppow
The field strength tuner is a Sarkes Tarzian. These were
used in nearly all TV sets for years. The RCA tuner looks
like it predates the ST, maybe not. Erasers are pretty good
for polishing contacts but do take some metal off. Actually,
I don't know of anything that will fix oxidized contract
without removing some metal because the oxidation itself is
removed metal. If the thing is greasy try lighter fluid
(naphtha). This is a pretty commonly used solvent for camera
shutters, etc. Rinse it off with dry isopropyl alcohol,
which is sold in computer stores.
--
jughead
>
> ...back in the day, when we got a real ratty tuner, we'd send it in
> for a rebuild.
>
Hell, come to think of it, now that analog has gone byebye, all you
need is to get ch.4 (or ch.3) working solid, right? oc
John Stone
On 9/11/09 5:06 PM, in article
ba9123cb-3511-4b59...@u36g2000prn.googlegroups.com, "jughead"
<oldco...@gmail.com> wrote:
How hard would it be to rig up a video input?
Brenda Ann
>
> In the factory, I suppose they would have torn apart the tuner for a full
> rebuild followed by a realignment, or just thrown it in the garbage and
> installed a new one. Neither one of those things is gonna happen here.
>
> Not sure where to go with this. The tuner's pretty hopeless in this
> condition, and the one in my other CTC-11 is almost as bad.
>
Try some Tarn-X maybe? You could always solder the switches in place on Ch.
3 or 4? :)
CSquared
Hi Phil,
I doubt you are going to be able to get even a small eraser where it will do
much good in one of those tuners. (I've used a reasonably non-abrasive "Pink
Pearl" eraser on gold plated PCB contacts with good results though, since
access is not an issue.) I would definitely recommend against using any
"gritty" eraser on any sort of switch contacts. I always used the contact
cleaner spray on tuners like the one in your picture with no apparent bad
effects that I know of. I did hear at one time (I think around 1960) that
the spray would dissolve or soften some part/s of certain tuners, but I
don't remember the brand. Back then I was personally dealing only with BW
sets though.
I finally gave my color RCA roundie away several years ago because I got
tired of replacing the nuvistor and fighting to keep the horizontal sweep
and high voltage section going. As a "poor tech" it was our only TV for a
few years. The guy I gave it to said the flyback died shortly after he got
it. Oh well...
One thing you might want to check in the tuner is to look very carefully for
a burned resistor under/behind some of the other stuff. In a very few cases
I was lucky enough to find this in some of these tuners and effect a fairly
easy repair. Sometimes the resistor is really burned in half and the pieces
make contact or not depending on slight pressure from turning the channel
selector. This can sometimes produce the symptom you describe.
Luck,
Charlie Carothers
--
My email address is csquared3 at tx dot rr dot com
Phil Nelson
> byebye, all you need is to get ch.4 (or ch.3) working
> solid, right? oc
Kinda, but I have different devices for output. A video player may use
channel 3 or 4. My pattern generator uses 5 or 6. Some of my restored TVs
are better on one channel than another.
I just got a Blonder-Tongue AM60-550A agile modulator to use as a home
transmitter (a $26 bargain on eBay). Works great and I can select any VHF
channel 2-13 or UHF up to 99. If I set it to broadcast thru the house on,
say, channel 7, then it's nice if my TVs receive 7. Or whatever.
One of these days, I'm going to set up a "TV party" for fun. A pile of
restored TVs, including things like a Sony Watchman or Sharp 3LS36 mini
color set, all receiving the same program over ANTENNAS the way Nature
intended. I may even include my decrepit Philco Safari if I can find its
oddball power cord. It may take a while to find out what is the best
compromise channel for all of them to receive.
Phil Nelson
Phil Nelson
> is to look very carefully for a burned resistor
Thanks for the tip. It can't hurt to take a look!
Phil
Bill M
>
> I just got a Blonder-Tongue AM60-550A agile modulator to use as a home
> transmitter (a $26 bargain on eBay). Works great and I can select any
> VHF channel 2-13 or UHF up to 99.
Just to pick nits...
I don't think this modulator will do UHF channels. (not sure of the A
suffix) It will, however, do the cable channels that fall in the
spectrum up to 550 MHz up to ch. 78. That's roughly up to UHF channel
26 although the frequencies are different.
Those 90s channels are in the FM and Aircraft band spectrum.
I only point that out because if a guy was attempting to evaluate or
align a UHF tuner using one of these it could be confusing.
-Bill
Bob
>
> How hard would it be to rig up a video input?
It can be quite a challenge if the TV takes the sync signal off ahead of
the video detector.
Michael A. Terrell
Phil Nelson wrote:
>
> Here's the RCA TV tuner in all its wafer-y glory. The set dates from 1961.
> Wafer tuners were also used in my cheapest b/w sets from the 1940s.
>
> http://antiqueradio.org/art/temp/DirtyTuner.jpg
>
> Someone thoughtfully discarded the shields, so it got plenty dirty.
>
> Here's the tuner in my TV field strength meter. It makes the RCA tuner look
> like a cheap toy. I gather this is a turret type.
>
> http://antiqueradio.org/art/temp/FieldStrengthMeterTuner.jpg
>
> I'm taking that as a No from Michael on polishing with a pencil eraser :-)
Phil, if you can get to the contacts try a thin strip of business
card dipped in contact cleaner to clean the contacts on the switch
wafers. It will slip between the pairs of leaf contacts and the
slightly coarse paper will polish the remaining metal.
I think I still have a few RCA tuners, but they were for the CTC-38
family. If the core is the same, the shafts can be exchanged on a lot of
versions. If I run into them, I'll try to remember to let yo know. I
also had some CTC-38 convergence panels somewhere that had good pots and
some good coils left.
Phil Nelson
> a UHF tuner using one of these it could be confusing.
No problem. I think I get it. All of my old TVs are VHF only, so I didn't
investigate what those other funny numbers meant :-)
My younger son is home from college for the weekend, so I subjected the kids
to a demo of my new TV station. I hooked up TVs around the house until I ran
out of rabbit ears. "Look," I would say, dragging them into another room,
"here is still another vintage TV playing the movie coming out of our
satellite dish, yet notice there is no pesky cable connecting the TV to a
satellite box. Nothing but an A-N-T-E-N-N-A! The signal is coming straight
out of the air. Look at this Sony Watchman in my hand. It keeps playing the
same movie no matter where we go. This is how tele-vision worked in Ye Olden
Dayes!"
They were rolling their eyes after about the fourth room, but grudgingly
agreed that it was cool. It was either that, or Dad cashes in their college
money to buy a red Porsche.
Phil
jughead
>
> How hard would it be to rig up a video input?
>
hard. But you'd need audio too. Audio could go in at the top of the
volume control. Video could go in right after the video detector diode
and just before the 3.58 chroma takeoff (since composite video
contains luma, blanking and sync, plus the 3.58 color carrier). Since
it's coming in at line level, it'd need some attenuation. Maybe Phil
could post the parts of the schematic showing the vid.detector, chroma
and sync takeoffs, and the volume control areas. :)
oc
Phil Nelson
> showing the vid.detector, chroma and sync takeoffs,
> and the volume control areas.
How's this?
http://antiqueradio.org/art/temp/RCACTC-11SoundTakeoffSchem.jpg
Phil
Bill Cohn
one volt of video from a DVD player. Also this TV has a high level audio
detector so it does not have a first audio stage only an audio output.
It would need more drive than the level from a DVD player for correct audio.
Bill - N9MHT
jughead
>
> The level of the video out of the detector is actually higher than the
> one volt of video from a DVD player.
>
>
> Also this TV has a high level audio
> detector so it does not have a first audio stage only an audio output.
> It would need more drive than the level from a DVD player for correct audio.
>
oc
John Stone
On 9/12/09 1:30 PM, in article
1c301e8a-d968-4a64...@l35g2000pra.googlegroups.com, "jughead"
<oldco...@gmail.com> wrote:
I'd assume audio would be easy. Just a switch at the top of the volume
control. My thinking is that you could potentially get a much better picture
from one of these sets used in this way, since all modern source components
have composite video out. You would eliminate the tuner which we know is
problematic, and the IF's which probably aren't in perfect alignment after
all this time.
jughead
advantage of A-V inputs would be circumventing the flaky tuners. oc
jughead
This is a reply to a poster over in the VideoKarma forum
regarding the tuner-
"By golly it's a shot in the dark, but I have seen a few cases where a
wafer was loose on the shaft, that is, the rotary part of the switch
was "un-keyed" from the shaft. You have to get in there with good
light and see if each rotor is turning in solidarity with the shaft.
If one is loose, you have to get it into proper position on the shaft
and epoxy it." oc
Bill Cohn
the video stages and do the impedance match for the video or if you want
a tube could be put into service. The same would be true for a furst
audio stage,
I would just fix the crappy RCA switch tuner. RCA seemed to like switch
tuners rather than the turret style, it must have been a cost issue at
the time.
Bill Cohn - N9MHT
Scott W. Harvey
>> Um.. since one section (or pole) of the
>> switch kills luminance when in the 'service'
>> position, check to be sure it's making proper
>> contact when in the 'normal' position.
>
> What can I say -- Bill rules.
>
> http://antiqueradio.org/art/temp/Napoleon1.jpg
>
> http://antiqueradio.org/art/temp/Napoleon2.jpg
>
> Amazing what a little spritz of DeOxit can do. Next time I find a CTC-11
> in a garage, I will not leave out that switch when cleaning the usual
> suspects!
>
What amazing luck, Phil.... the switch probably got all crusty before
the original owner could use the set until the CRT breathed its
last....nice bright picture you got there.
For a dollar (and an initial attempt at repair) that picture looks awesome.
-Scott
Scott W. Harvey
>
> I hope something can be done with this awful tuner. I carefully put some
> DeOxit on the wafer contacts, but it still barely tunes in anything
> unless you stick it between two channels. Maybe I can reach in with a
> little piece of pencil eraser held in long tweezers and polish away. But
> there are places you just can't reach.
>
> I got an "RCA Color TV Service Manual" from the library, and it briefly
> mentions tuner cleaning. The factory recommended Clorathene NU (?) as a
> cleaner, with a little bristle brush. Other cleaners may damage plastic
> parts, it warns. I gather this kind of cleaning would have been done
> with the tuner completely disassembled on the bench. Do not move the
> shaft while cleaning, it warns, as dry contacts may be permanently
> scored and damaged.
Nobody in the mom-and-pop service business did that back in the day. The
service shop would instead send the tuner to a company that specialized
in rebuilding TV tuners-it was all they did. A quick look in the back of
an old Photofact Index will show ads for several of these companies, who
provided a hell of a service for 10 or 15 bucks. They would clean the
tuner and confirm that it was aligned to factory specs and touch things
up if it wasn't. This was hours of work for a TV tech who had to set up
his test bench every time to do it, minutes of work for a specialized
outfit that had test jigs for every popular tuner already set up and the
expertise to know how to disassemble the tuner promptly.
-Scott
jughead
the switch rotors are keyed solidly to the shaft, with no backlash or
play? I have seen this problem a few times before (though not in
RCAs), even with one rotor completely 'stripped' and not turning at
all with the shaft. oc
Phil Nelson
> original owner could use the set until the CRT breathed its last....nice
> bright picture you got there.
>
> For a dollar (and an initial attempt at repair) that picture looks
> awesome.
Yeah, I'm guessing the set was retired when the thermistor off the power
switch fell apart and the set went completely dead. Then it just sat for a
long time.
There's an opening in the back for the service switch, so that could also
have been left a little out of position if the owner was poking around in a
vain attempt to make it come back to life.
Nice to have one wake up and play with minimal work, in any case. My
projects don't always work out this way!
Phil Nelson
Scott W. Harvey
I'm with you.....unless the tuner has been flipped through the channels
to the point of contact wear-out (and Phil already has/had a JVC
Videotron that suffers from this issue), then cleaning up the tuner is
the likely fix, especially considering that he has now discovered that
the cover has been removed for god-knows-how-long.
I used to have a tool-i don't know who makes it- that would have been
perfect for this. It looks like a blue mechanical pencil, except that it
has incredibly stiff, coarse bristles on the end of it. The intent of
the tool was to remove corrosion and oxidation much like a pencil eraser
can do, but with much less effort and pressure needed.
If those wafer contacts are worn to the point of permanent fatigue, then
I am at a loss.
Which brings up a related point.....
I used to know a couple of old-timers-long dead now-who could fabricate
replacement wafers for almost anything by parting out existing NOS wafer
switches and modifying them through a combination of dremeling,
riveting, and magic, so I know that is at least theoretically possible.
Perhaps that is a small business that can be grown organically by
someone, perhaps Mark Oppat. Almost everyone who has been at this awhile
has seen at least one case of otherwise viable equipment relegated to
the shelf because of a hopelessly damaged switch wafer (and I have two
items in the shop right now so affected). It would be good to have a
resource that could fabricate new ones like Mark does with volume controls.
-Scott
-Scott
Phil Nelson
How do you remember these things? Yes, the guy who fixed my VideoSphere had
been a JVC factory tech and described how they repaired those tuners. Fling
the old one in the garbage and pop in a new one.
> It looks like a blue mechanical pencil, except that it has incredibly
> stiff, coarse bristles on the end of it.
I have seen mention of fiberglas brushes like this:
http://www.micromark.com/ULTRA-MICRO-FIBERGLASS-BRUSH,7850.html
http://www.exceltahobby.com/shop.php/brushes/267a-fiberglass-brush-refills/p_92.html
If you search on Google, you'll find more. Unless this tuner were
disassembled, something in a pencil body couldn't reach the contacts (wrong
angle). But, aha -- I could order some brush refills and hold a piece of one
sideways in a long tweezers. Or drill a little hole in the end of a
chopstick and superglue in a refill end to make an angled brush. Looks like
something that could be used very gently.
Phil Nelson