Topic: AM Radio Restoration

[Angela]

I'm wondering if anyone would be willing to give me some tips and/or recommendations concerning my AM radio (picture below). IMHO, it's a REALLY nice survior, the white and chrome stripes on the face are in superb condition and the zinc plating on the case, inside and out, remains in pretty nice condition. I don't see any rust. All the preset buttons work smoothly. I don't see any physical signs that the capacitors have gotten hot or exploded, which I've seen on several radios I've taken apart.
I'm debating the next step.... do I send it out for a full resto and have all the caps replaced? Do I just spend some time cleaning and put it in the car? Something in between those extremes?

If I were to remove the preset buttons for better cleaning and polishing, what's the best way to remove them? Or is it best not to remove them?

I think the only thing that makes me want to discuss sending it out for a full restoration is that I've read the old caps can explode and I'd prefer not to start a fire in a car I've been restpring for over a decade. :-)

Are there any radio restoration shops you guys would recommend? 

[rharlan]

I took mine to Fred's Classic Auto Radios & Clocks in Lenexa, KS (Kansas City area). He did a nice job and reasonable.
http://www.fredsclassicradios.com/index.html

[Angela]

Well, had thought my radio was in perfect working condition, but I was wrong. Turns out that even with the volume turned to maximum, the output is very quite. I don't think I could hear it with the engine running. It otherwise tunes into stations just fine. I plugged in a spare radio with the same part number, into the same car with the same speaker and antenna and that radio was perhaps 100 times louder.

I chatted with Fred from Fred's classics, as well as one other company and both seem to think the radio is repairable and suggested the problem may be with the capacitors having dried up over the decades.

I have somewhat changed my mind, in that I'm not sure I want to pay for a full restoration when it's already in superb original condition (cosmetically). The cost for repair is the same, however, whether I just have the caps replaced or if they "restore" it and replace the caps.

Has anyone repaired or replaced parts in these 7TPZ radios? I just ordered the Photofacts AR-41 but don't have it in my hands yet. I'm wondering if it's always the same specific caps that need to be replaced and whether or not anyone can offer some guidance. I think I am now considering repairing it myself, or at least trying to figure out if I can, before I spend a couple hundred bucks to have it restored/repaired professionally.

[Bob Gaines]

Maybe buy a working one off of ebay for 30-75 .00 and replace the faceplate or other cosmetics from your under performing one.

[e093116]

I repaired a 70 AM/FM last year with the same problem you describe.  By replacing a cap in each speaker output ckt I was able to get appropriate volume out of the radio.

Since I believe your AM radio has only one output channel, you should only have to replace one cap.

Use your Sam's book to identify the electrolytic capacitor closest to the speaker and replace that cap.

Caps do have a polarity, so it is possible to install backwards.  Read up on the internet to convince yourself you know how to identify which lead is which so you get the polarity right when you install it.

The Sam's book will probably tell you something like a 0.02 uF cap is needed with a voltage rating of 30V.  You might have a hard time finding this exact same spec cap, but as long as you get a cap with a higher voltage rating you'll be ok.  Think of the voltage rating like a pressure rating for pipe...so the voltage listed is really the minimum spec and it is ok to use something with a higher voltage rating.   I think 50V is a common rating you'll probably find.  Don't worry if the size/shape of the new part is not exactly the same as the old part, the physical size/shape will most likely be different between the two parts...just match the microfarad rating as close as possible.

You should be able to get the cap(s) you need at your local Radio Shack for $2-$3 each.  They should be a stock item so you won't even have to wait for an order to come in.

You may want to consider replacing all of the electrolytic caps while you have the radio open.  A "real" restoration will do this.  Replacing the one in the tone control ckt will help the sound quality.  I'd at least consider replacing this one while you're there if you don't want to do all of them.

You should be able to repair this radio yourself for under $10 in parts.  The sense of satisfaction at the end of the day will be priceless.  Good luck.

[jstefanick]

I have done this with my 66 Philco radio. Even though you have something more recent than that, this site should help with some knowledge of how to solder and remove old capacitors:

http://hurtle.com/cars/mustang/fixes/radio/

I also bought my capacitors at this company, digikey.com. I found my local Radio Shak woefully equipped for something like this.

The capacitors are definitely your issue-

I also bought the Sams Photofacts for my 6TPZ Philco radio. It tells exactly what capacitors to buy. The info posted by e093166 is also very informative. The size of the new capacitors will be very different than what is in there, it is the ratings that matter.

If you are handy with a solder gun, it can be done, if not, farm the job out.

[Angela]

Thanks for the info guys! I'll wait for the photofacts book to arrive and then I'll see if I can figure out which caps to replace.

Question: did you have to remove the circuit board to replace the caps? If yes, is that difficult?

[jstefanick]

You can do the job with the board still in the radio shell, your just melting solder and re-soldering them in, I didn't have to take it totally out like that.