radio repair for dummies?? - Chevelle Tech
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post #1 of 21 (permalink) Old Jan 15th, 05, 1:06 PM Thread Starter
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My '67 AM radio doesn't work. The light comes on and the dial and buttons work. But there is no sound. I've tried several different speakers.

I'm told the problem often is a blown transistor. Is elementary radio diagnosis and repair - finding the problem and replacing a transistor or something like that - something that a novice at radio repair can do?

Where would I find simple instructions on how to diagnose and fix the problem??
Thanks.
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post #2 of 21 (permalink) Old Jan 15th, 05, 1:30 PM
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northern,

I've a rudimentary knowledge of transistorized and solid state circuits (my degree is in electrical engineering) and based on my experience, I'd say "no." I'd look for a local radio repair shop with a "good old boy" who used to work on these radios (that's what I did with my '68 AM/FM) or a national shop that does this kind of work. Good luck with this.

Greg

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post #3 of 21 (permalink) Old Jan 15th, 05, 10:14 PM Thread Starter
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Yes, it would be nice to find someone who would not charge more than the radio is worth for looking at it.
One person suggested tapping the power transistor that they say sits on a heat sink on the outside of the radio case. Apparently that sometimes results in a temporary fix??
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post #4 of 21 (permalink) Old Jan 17th, 05, 12:50 PM
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Northern396,

If you can get a schematic for it, anyone good in electronics could most likely fix it. The key would be getting a set of schematics for it. Maybe someone can tell us how we could get a schematic, as I need one also for my 69.

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post #5 of 21 (permalink) Old Jan 17th, 05, 1:26 PM
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I did a Google search and found this place and many others.
http://techpreservation.dyndns.org/schematics/Delco.htm
This is their section for Delco schematics and you use the menu to select the model. Not too sure if that model number is easy to find or not. Good luck.
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post #6 of 21 (permalink) Old Jan 17th, 05, 2:09 PM Thread Starter
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That is a good idea. But I checked their site and they do not list model 986853, the model of the '67 Chevelle AM radio. Does anyone have details on this model?
Thanks
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post #7 of 21 (permalink) Old Jan 17th, 05, 7:40 PM
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Hey Northern,

My dad works on all kinds of radios, including old car radios. Drop me an email at [email protected]

MrSS396
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post #8 of 21 (permalink) Old Jan 17th, 05, 8:01 PM
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You don't need a schematic if you are experienced in electronics. The bottom line is, if you are not familiar, or have experience, you should NOT be attempting to repair your radio.

An open audio output transistor is quite likely, but this is just the tip of the iceberg. When it goes it can/will take the fusible emitter resistor with it as an example. You may also have bias problems in relationship to bad electrolytic capacitors which have gotten to an age where there life span has come to a useful end.

There are some preventative things that would be "caught" by a pro that would prevent future failures, so I'm sorry to say there is no "radio repair for dummies".

Not trying to be negative, just truthful.

This is coming from someone who has repaired everything from a 1948 Ford Adjust-O-Matic radio, to a 1998 Pontiac Grand Prix ETR radio receiver.
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post #9 of 21 (permalink) Old Jul 12th, 19, 1:38 PM
 
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Hey my grandpa has a 67 Chevelle am radio too. And his is doing the same thing. He told me that those radio we’re transistors which went bad after a long period of time. He said his quit working in the 80s, and said that GM said it couldn’t be fixed.
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post #10 of 21 (permalink) Old Jul 12th, 19, 1:58 PM
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Re: radio repair for dummies??

14 1/2 year old thread ...

When I worked in a Chevrolet parts department in 1956, one of my jobs was to take a load of non working radios to a radio shop and bring back a load of working radios.

The techs just switched them when they came into the shop.
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post #11 of 21 (permalink) Old Jul 12th, 19, 8:07 PM
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Re: radio repair for dummies??

The electrolytic capacitors usually have dried out and lose their capacitance. If its just a single cap on the board, replacing these is usually easy if you can still read the required capacitance and voltage on the part. Mouser Electronics and Digi-Key will have these piece parts for cheap - shipping will be much more than the value of the parts.

Finding the defective cap on the board is usually easy. As long as we are discussing radios WITHOUT vacuum tubes, these are all low voltage radios with little chance of electrical shock. For the radios without vacuum tubes, it is often possible to detect the bad capacitor simply by placing your finger on the leads of each capacitor on the printed side of the board - the flesh of your finger supplies a little capacitance. The sound out of the speaker will sometimes return temporarily under these conditions while your finger is in place. Note the values on the capacitor, procure it and then carefully remove the old one. Install the new one CAREFULLY noting the polarity on the side of the capacitor. Get this wrong and your new cap will get hot, bulge out and explode like a small firecracker.

The problem is the multi-value capacitors in a metal can within the radio. Those parts are tough to find that still work and have also not already dried out. These radios are scrap value to most of us at that point unless you want to send it to a true professional radio restorer. They might have the parts or are willing to do the more tedious re-design work to find modern alternative parts.

All bets are off for vacuum tube radios. Their voltages can be deadly unless you are skilled at bleeding off stored power in the capacitors that still store energy.

Rick
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post #12 of 21 (permalink) Old Jul 13th, 19, 12:22 AM
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Re: radio repair for dummies??

Funny, Dean's response conveyed no info. Why bother?
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post #13 of 21 (permalink) Old Jul 13th, 19, 7:44 AM
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Re: radio repair for dummies??

I have the AM radio in my 69 working nicely. I just cleaned it with good quality spray and then lubed it with good quality lube. I clipped the wire that feeds the amp with the AM radio signal and put a switch on it with a mini jack cord. I also used two 1K resisters one for each channel, on the mini jack. The switch goes from radio to input. I have a I-Pod connected to it. The sound is amazing! That old radio sounds great for what it is. I'm sure getting a strong clear signal from the I-Pod helps.
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post #14 of 21 (permalink) Old Jul 13th, 19, 8:09 AM
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Re: radio repair for dummies??

Normally when the big capacitor goes out all you get is a buzzing noise and you can replace it with any capacitor that has an equal or higher microfarad rating. The transistors are the big metal pieces attached to the chassis and the pn is written on the case.

In order to test these radios you need a power, a solid chassis ground, a known good 8-10 ohm speaker, and antenna hook up. Note that the old radios only had a positive speaker output from the radio and chassis ground served as the negative side.

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post #15 of 21 (permalink) Old Jul 13th, 19, 10:32 AM
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Re: radio repair for dummies??

Quote:
Originally Posted by 66sc View Post
Funny, Dean's response conveyed no info. Why bother?
To let people know that northern 396's radio problem was 14 1/2 years ago

So what info is in your post Kev?
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