Author Topic: Radio Shack Frequency counter model 22-306 gone deaf. (Read 8613 times)

Lightages · « **on:** January 12, 2015, 08:37:02 am »

I seem to remember somewhere on the internet a comment made by someone about the front end amplifier getting fried easily on the 22-306. Mine is basically deaf and I was looking around but found nothing.

There is this thread on the forums about another repair:
https://www.eevblog.com/forum/repair/radioshack-22-306-frequency-counter-teardown-and-repair/msg155276/#msg155276

But it does not relate to my problem. I remember the front end amp transistor being something like MFJ47 or something like that but I am sure I am wrong. Anybody have any schemattics, links, suggestions?

Alex Eisenhut · « **Reply #1 on:** January 12, 2015, 05:04:25 pm »

Hmm, I have the service manual somewhere.

Alex Eisenhut · « **Reply #2 on:** January 12, 2015, 06:02:40 pm »

Just some quick n dirty camera shots.

Alex Eisenhut · « **Reply #3 on:** January 12, 2015, 06:10:57 pm »

troubleshooting chart

I'd go through the basic power supply - reset ckt - oscillator checks first.

But the thing uses a center negative barrel connector for external DC and it's not smart enough to tell alkalines from nicads by itself, you have to set a switch.

If by "deaf" you mean "no display at all", yes, check the whole power supply section first. One hopes it's not the processor that's fried.

Lightages · « **Reply #4 on:** January 12, 2015, 06:11:23 pm »

That is very helpful Alex! Thank you.

Is there any chance of you scanning the whole document and making it available to me in some form? I am willing to pay a fee.

Lightages · « **Reply #5 on:** January 12, 2015, 06:13:36 pm »

It is functioning but not displaying stable values and it does not respond to sufficiently large amplitudes as it should.

Alex Eisenhut · « **Reply #6 on:** January 12, 2015, 06:58:59 pm »

Quote from: Lightages on January 12, 2015, 06:11:23 pm

That is very helpful Alex! Thank you.

Is there any chance of you scanning the whole document and making it available to me in some form? I am willing to pay a fee.

I'll think about it, the Canon scanning software is atrocious, I gotta see if I can use something else to stitch together 20 or so scans into a PDF.

When you scan a manual, alternate pages are flipped but there's no simple way to tell the stupid software about it.

Lightages · « **Reply #7 on:** January 12, 2015, 10:07:56 pm »

Don't worry about the order or orientation of anything. If you have the time, just scan to jpgs or whatever. I will sort it out on my end.

JoeO · « **Reply #8 on:** January 13, 2015, 03:50:44 am »

How about this?

http://www.radioscanner.ru/forum/topic45103.html

3rd post down from the top.

Lightages · « **Reply #9 on:** January 13, 2015, 04:16:37 am »

JoeO:

Thanks for the link. I am not sure it is useful though as all the jpg file names reference the 22-305

JoeO · « **Reply #10 on:** January 13, 2015, 12:14:24 pm »

Sorry: I put 22-306 into Google search and I never noticed that they listed 22-305 as a result.

Alex Eisenhut · « **Reply #11 on:** January 13, 2015, 04:12:25 pm »

alright alright, I'll try to use the scanner... It's only 24 pages.

Lightages · « **Reply #12 on:** January 13, 2015, 05:14:20 pm »

I appreciate the effort. Thank you

PA0PBZ · « **Reply #13 on:** January 13, 2015, 07:59:27 pm »

Quote from: Lightages on January 12, 2015, 06:13:36 pm

It is functioning but not displaying stable values and it does not respond to sufficiently large amplitudes as it should.

On what range is that?

Lightages · « **Reply #14 on:** January 14, 2015, 01:03:18 am »

I don't remember exactly the conditions of the failures. I am sure though that it does not work on the low range.

PA0PBZ · « **Reply #15 on:** January 14, 2015, 09:17:07 am »

Quote from: Lightages on January 14, 2015, 01:03:18 am

I don't remember exactly the conditions of the failures. I am sure though that it does not work on the low range.

I'm asking because each of the ranges follows a different path:

1Hz - 10Mhz: Directly to U3
1Mhz - 50Mhz: This uses the pre-amp on the top left, then the prescaler U4
50Mhz - 1.3Ghz: Goes directly to the prescaler U4.

So knowing where the problem is would be helpful in finding what's wrong.

Alex Eisenhut · « **Reply #16 on:** January 14, 2015, 08:13:42 pm »

My scanner finally connected again to my wi-fi router. Don't know why Canon makes such opaque, bloated, and bizarre software. "Please wait a while" indeed.

I miss my old cheap and cheerful flatbed USB scanner.

Lightages · « **Reply #17 on:** January 16, 2015, 09:18:55 pm »

Thank you very much to Alex for his help and time with the service manual. It will be very helpful.

PAOPBZ, yes I now have a path to follow, thank you.

Alex Eisenhut · « **Reply #18 on:** January 16, 2015, 10:58:37 pm »

Quote from: Lightages on January 16, 2015, 09:18:55 pm

Thank you very much to Alex for his help and time with the service manual. It will be very helpful.

PAOPBZ, yes I now have a path to follow, thank you.

It may eventually also show up at BAMA in the Radio Shack section. I am so annoyed at the Canon software that I skipped trying to stitch the schematic pages together.

Canon makes one of the worst software suites I've ever seen. Makes Sonic Stage look like iTunes.


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Author Topic: Radio Shack Frequency counter model 22-306 gone deaf. (Read 8613 times)

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