I have a crusty MoPar Chrysler Model 393 AM Radio 8 track player that does not work. When I apply power, the tape drive works perfectly. I get a good hiss from both speakers with the tape playing, and with the AM radio on (when I pull the tape out). Whenever the deck is on, I get that hiss, and both of what I believe are the output transistors (on the outside of the front of the unit) are both warm, but not hot. Where should I proceed to fix this problem? I have experience with AA5 tube radios, but have not really done that much work on transistorised equipment. Here is the schematic.

http://antiqueradios.com/gallery/v/temp ... ewsIndex=1

There could be several reasons as to why you are experiencing the hiss, but have you tried just cleaning the tape/radio slide switch and the volume controls with a can of Radio Shack (Cat. No. 64-4315) Cleaner and Lubricant? Make sure that you get ample cleaner into that slide switch, and the volume on/off switch also. Sometimes a simple fix is all that it is required to bring these radios back to life.

If the cleaning doesn't help, then check out the volume on/off switch and the volume rheostat with a good digital ohmmeter. A busted volume control could be a good candidate for the problem that you are experiencing.

Inject a signal from your signal injector starting from the output bases and work forward looking for the fault.

Lots of tuner cleaner, and generally messing with it worked. The loudness of the audio slowly came back over a peroid of a half an hour. The AM radio works great now as well. Cleaned the head, and the 8 track sounds as good as new. The only problem to tackle is the little slip wheel in the tuning knob. The knob turns fine, and the tuning sugs seem to move fine, if a bit sluggish. There seems to be more resistance than I would like in the slugs and the worm gear that drive them. It seems like there was some sort of rubber washer between the tuning knob thumbwheel and the rest of the tuner, that rubber washer thingey seems to have crumbled away. It was a limited slip design that would prevent people from damaging the radio by tuning beyond the ends of the band.

I'm very glad that you got the radio working. Nice job!!!

Nicely done.

Tuner cleaner is great, but its expensive.
Good old 90% isopropanol works wonders, even for cleaning belts and pickup heads.

Glad you're almost there !

~ Mitch ~

PBPP wrote: "Tuner cleaner is great, but its expensive.
Good old 90% isopropanol works wonders, even for cleaning belts and pickup heads."


Rubbing alcohol would be excellent for cleaning belts and pickup heads, but you would never ever trust it for cleaning switches.

Works great for cleaning switches and dirty pots. - No complaints.
So why would you not trust it for cleaning switches?

~ Mitch ~

Trial & error.