Radio repair advice, please

[Ivan Vegvary]

Just picked up a Zenith Royal 2000 (1961) for free at a garage sale. Downloaded Photofact from web site.
I'm sort of a newbie at this.
Will probably need to replace electrolytics. Have working Heathkit (1Mz) oscilloscope and DMM's.
What is the least expensive way (equipment) to inject a signal (Rf, If, etc.) into this unit in case cap replacement is not enough.
Don't mind spending a few bucks.
Also, is an SER meter worth getting, or, simply replace all caps?

Thank you, Ivan Vegvary

[Ralph Mowery]

"Ivan Vegvary" <ivanv...@gmail.com> wrote in message
news:2ff4b805-88ef-4146...@googlegroups.com...

You might look on ebay for some of the old signal generators. There are
also some signal generators and some are in kit form from China called DDS.

The simpliest way I know of is something I used a long time ago. It was
something I built out of parts I had from a magazine. It was just a
multivibrator operating at some audio frequency ,but it had harmonics way up
into the RF range. There was also some comercial versions of it. I think
it only used 2 transistors a few resistors and capacitors. Like this ebay
number. You start at the audio stage and work to the rf area. I usually
put it on the volume control pot first. That seperated most of the audio
stages from the RF section.
One of the beter ways to trouble shoot equipment is to do the half way
method. Start about half way through the circuit and when you loose or
gain the signal, go half way to the last or next section.



251121615025

[Cursitor Doom]

You'd have to be nuts to buy an ESR meter just for one radio. Save the
money and just replace all the electrolytics.
For a signal to inject a single stage oscillator for the required
frequency would be the cheapest solution; loads of schematics on the web
and it doesn't need to be a crystal controlled job.

[John-Del]

ESR meters are cheap and reliable. Back when I bought my first one in 1985, they were $1200. I still have it.

For what they cost these days, there's no reason a hobbyist shouldn't own one.

[John Robertson]

Plus, for ones like the Bob Parker design, you get some soldering
practice as well!

John :-#)#

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[Cursitor Doom]

They're not *that* cheap (I bought one a few weeks ago and it cost me 90
quid ($135) and if the OP is only going to be doing the one radio, which
he got for free, he'd have to be nuts buy a meter!

[Ralph Mowery]

"Cursitor Doom" <cu...@notformail.com> wrote in message
news:mgem5b$b71$2...@dont-email.me...

>>> ESR meters are cheap and reliable. Back when I bought my first one in
>> 1985, they were $1200. I still have it.
>>
>> For what they cost these days, there's no reason a hobbyist shouldn't
>> own one.
>
> They're not *that* cheap (I bought one a few weeks ago and it cost me 90
> quid ($135) and if the OP is only going to be doing the one radio, which
> he got for free, he'd have to be nuts buy a meter!

If you have to pay around $ 100 that is too much for just a couple of
repairs. For less than $ 20 including shipping, anyone that wants something
inexpensive to check components should check this or one like it out on
ebay. Peak makes about the same thing in a case for around $ 100 but they
make one for transistors and another for the capacitors and resistors. They
charge you twice for the same thing.

[Cursitor Doom]

On Sun, 12 Apr 2015 17:09:31 -0400, Ralph Mowery wrote:

> If you have to pay around $ 100 that is too much for just a couple of
> repairs. For less than $ 20 including shipping, anyone that wants
> something inexpensive to check components should check this or one like
> it out on ebay. Peak makes about the same thing in a case for around $
> 100 but they make one for transistors and another for the capacitors and
> resistors. They charge you twice for the same thing.

The one I bought is a Peak. Good quality item, but all it measures is ESR.

[Michael Black]

Except, these electrolytics are just handling AC line or audio
frequencies. They may have expired, but not from strain of 100KHz or
whatever.

Also, they aren't used in some highly-feedbacked circuit, as is the case
with switching supplies. Transistor radios use more electrolytics than
tube radios (which could be often diagnosed by listening to the radio, hum
meant a new filter capacitor, low audio gain meant a new cathode bypass
capacitor in the audio stages), but they are straightforward. They are
either bypassing the emitter resistor in the audio stages, coupling audio
between stages, or to provide a low impedance on the "B+" line. It's
daunting to look at, all those electrolytics in a transistor radio, but
you don't need anything fancy to replace them with, and if you aren't
going to troubleshoot (low audio, bad bypass or electrolytic coupling
capacitor, motorboating, bad electrolytic on the "B+" line), then just
replacing them all is relatively cheap (compared to buying an ESR meter)
and fairly fast.

Michael

[gregz]

I'll see how my $15 component tester works when I get it.

Greg

[Ivan Vegvary]

Thanks everyone for your thoughtful answers.
Reason for ESR meter is I do have 2 additional radios (not a priority) and 3 old guitar amps that I might get to in my old age.

A previous poster (above) referred to an inexpensive ESR (possibly a kit) but did not leave a link. Any suggestions?

Ivan Vegvary

[Sofa Slug]

First of all, there are really only a handful of electrolytics in the
2000, many of the caps are ceramic (you don't need an ESR meter). The
most likely problem you will run into is intermittents in transistor
sockets, switches, etc. - easily fixed with re-seating &/or some
contact cleaner. The dial strings on these also have a habit of
slipping/breaking and are kind of tricky to get to.

I think you are putting the cart before the horse, here. Unless you have
some heavy corrosion or other damage, you have a good chance of coaxing
some audio from the set. If you have a scope, you can generally use an
over-the-air signal to check out the rest of it. Unless the front end is
totally dead (unlikely scenario), I wouldn't worry about getting a
generator right away.

[Sofa Slug]

The "Blue" ESR meter is regarded as one of the best. You can get the kit
directly from here:
<http://shop.anatekcorp.com/products/component-analyzers/blue-esr-kit/?query=category.eq.Component%20Analyzers&back=products>

[Ralph Mowery]

"Sofa Slug" <sofa...@invalid.invalid> wrote in message
news:mggpt0$9et$1...@dont-email.me...

It would be interisting to compair that with one of the $ 20 component
testers from China.

One thing that I think might be wrong with the testers is they use almost no
voltage (less than 1/4 of a volt). I just wonder if the usually higher
voltages the cpacitors operate under would make any differance, especially
the power supplies that have over 100 volts on them.

[jurb...@gmail.com]

The lower the better when it comes to voltage.

I don't use an ESR meter anymore, I use a 1 kHz 400 mV square wave with a source impedance of about 360 ohms. I apply it to the scope probe and the DUT and observe the rising and falling sides of the resultant waveform.

The Creative Electronics Wonderbox used less. One elcheapo meter I ran across used less.

Less than a half volt is good because then semiconductor junctions do not interfere with the readings.

I am not that crazy fond of digital meters when it comes to this. The Dick Smith is good and everything and there was another one I used for a while. The one I used went through a rigamaroll every time you put the probes on "discharging". Fuck discharging, you have a coupling cap internal - use it and measure the ESR NOW. I have 50 to test in this unit and I got about 10 minutes to do it.

I just want the needle to move or a bar graph of LEDs to light up or something. I do not need to know the ESR to the fifth decimal place. Nor do I need it to beep. Actually if someone came up witt an audio indication of a useful type I would be interested.

Now the problem with that is if it say, emits a sound when the cap is good, fine. But it is hard to hear different levels of sound. More accurate would be if the DUT shorted out the audio, but that would mean the audio going on all the time until a good capacitor is connected to the test leads. When completely silent the cap is good, but htis method would be quite annoying.

I do not need a digital readout. The Dick Smith is a fine and accurate instrument, but when my boots are on the ground I just need something quick. This is not formulating some delicacy with saffron and truffles, this is making chili. Is it an ohm or less or not ? And then in some instances, how much less ? If the leads are farther apart in solid state equipment you usually want it under an ohm. The smaller ones are not as critical, that's why they used smaller ones.

[Chuck]

Another fairly common problem is one or more of the germanium
transistors becoming leaky.

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