1967 Radio Volume Has Diminished

[Ian H.]

The sound coming from my speaker is very faint. Same on AM and FM. It is as if there is no amplification. The volume control does NOT have and has never had any scratching noise and turning the volume knob varies it from nothing to faint.

One day it was fine, the next day it was like this.

Before sending it away, is there anything I can try? I don't want to spray any cleaners as some old posts have warned against it.

[Stephen L.]

Re: 1967 Radio Volume Has Diminished

Sounds like your power output transistor has gone south.... or try another antenna plugged directly into the radio as a test of that device.

[Larry M.]

Re: 1967 Radio Volume Has Diminished

The volume control rheostat gets oxidized from age and moisture and can cause this. My 1967 car is the same way. Some folks have had success using a electronic contact cleaner and spraying it into the rheostat. The archives have information.

Since my car also has side pipes, I don't use the radio. One day I may send it out for a good cleaning and refurbishment.

Larry

[Carnell M.]

Re: 1967 Radio Volume Has Diminished

The guy that rebuilt my radio advised AGAINST spraying the contact cleaner because it messes up something in the radio. ( I had already done it)

[Wayne M.]

Re: 1967 Radio Volume Has Diminished

The sound coming from my speaker is very faint. Same on AM and FM. It is as if there is no amplification. .....

'65 Delco radio service manual says that if it's the big DS-501 output transistor (on the back heat sink), then there will be no "THUMP" when you turn on the radio.

[Jack H.]

Re: 1967 Radio Volume Has Diminished

Yeah, that is talking to a basket case DS-501...one that's totally failed. It's possible (but not all that common) for transistors to be 'wounded' but not dead. They can suffer from junction punch-through where a lot of 'funnies' result including diminished output and/or Jeckyl/Hyde operation. The later is particularly annoying for a tech to trouble shoot. It results from the junction puncture 'repairing' itself by oxide forming to cover/plug the puncture when bias voltage is removed. But, the puncture re-opening when the part is exercised electrically. This is NOT a common situation and can be diagnosed on a transistor curve trace fixture

[Gerard F.]

Re: 1967 Radio Volume Has Diminished

Ian,

From your post, it sounds like the main transistor is out (DS501). They go out if the speaker has been changed to one with the wrong ohms rating.
Also it could be the volume/tone switch.

Had a problem with my 67 radio a few years ago after I put in a generic speaker. Blew the transistor, and I had tried to clean the volume/tone switch too many times with that electronics spray.

Had to change the transistor and the volume/tone switch. Did it myself and touched up the soldering on a lot of wiring connections.
A replacement DS-501 is available from Radio Shack online, I forget where I got the new tone/volume switch but it is also available somewhere online, but expensive.

If you need a manual, wiring diagram and parts list of the 67 radio, send me an email with your email address. I have it pdf 'd somewhere on my computer.
But it is probably best to send it out to someone who knows what he is doing, and also restore/replace the visible parts on the dash.

But if you are electronically inclined and good with a soldering gun, you can do it yourself

[Timothy B.]

Re: 1967 Radio Volume Has Diminished

My 67 radio acts bad also, it's got faint volume on a strong FM station but nothing on AM or the other FM stations. This is after I sent it out for repair. I don't use it, (I take my wife with me) so I never think about trying to troubleshoot.

[Chuck M.]

Re: 1967 Radio Volume Has Diminished

Ian,
If you want to talk to someone before you send it out or try a DIY job give Jerry Rudbeck a call. He is an NCRS member and did a great job repairing our 67 radio. He will be more than willing to talk with you about the issues you are having.
http://www.electrodesign.us/index.htm
Jerry@ElectroDesign.US

Good Luck!
Chuck

[Ken A.]

Re: 1967 Radio Volume Has Diminished

I know where you can get a DS501 for a reasonable cost-but limit 1 per customer.

[Peter L.]

Re: 1967 Radio Volume Has Diminished

Tim - It sounds like another option is to add side pipes. Pete

[James W.]

Re: 1967 Radio Volume Has Diminished

I second the advice of giving Jerry Rudbeck a call. You won't find a better resource or someone will to discuss the problem and won't charge you clock time for the diagnosis. Contact him, you won't be sorry.

Regards,

James West

Ian,
If you want to talk to someone before you send it out or try a DIY job give Jerry Rudbeck a call. He is an NCRS member and did a great job repairing our 67 radio. He will be more than willing to talk with you about the issues you are having.
http://www.electrodesign.us/index.htm
Jerry@ElectroDesign.US

Good Luck!
Chuck

[Michael J.]

Re: 1967 Radio Volume Has Diminished

tim - it sounds like another option is to add side pipes. Pete

lol!