Mid year radio -volume knob static

[Gary N.]

If I move the volume knob on my 66' original radio I get a lot of static interference, Is there any possible fix for this short of pulling out the radio and sending ot off for a repair. It works fine except for the raspy static when turning up/down the volume.

[Alan D.]

Re: Mid year radio -volume knob static

Spray some light oil into control pot. (or Electrical cleaner)

[Duke W.]

Re: Mid year radio -volume knob static

Oil will make it worse by attracting dust. Use an electrical cleaner, sometimes known as "tv tuner cleaner". You should be able to find something suitable at any electrical supply store like Radio Shack or Fry's.

Those old mechanical tuners are basically variable capacitors, and dirt eventually contaminates them, which is what causes the static, especially when you move the plates by tuning the radio to a different station.

Duke

[Gary N.]

Re: Mid year radio -volume knob static

Spray some light oil into control pot. (or Electrical cleaner)

What is the control "pot"?

[Duke W.]

Re: Mid year radio -volume knob static

What is the control "pot"?

A "pot" is a potentiometer. (If you don't know what that is Google is your friend), but the radio tuning knob is not a pot. As I said previously, it's a variable capacitor.

If you don't know how a basic radio tuning circuit works, Google is...

Duke

[Stuart F.]

Re: Mid year radio -volume knob static

I keep a can of tuner bath in every room of my house, including the garage. I'm old fashion and still have some of the best Stereo components going with those I ordered from the PACEX catalog while in Viet Nam. I'm even going to try it on a SONY reel to reel tape deck that I brought back that has all solenoid controls, but the solenoids are hung up after all these years. I have some great 7" reels of Oriental music.

Stu Fox

[Stephen L.]

Re: Mid year radio -volume knob static

I had a similiar problem with my radio; Static when turning the volume control. I could get rid of it temporarily by turning the volume up/down many times until the static was gone. This would last for a few days.

I finally decided to fix the problem so I visited Jerry Rubeck and we removed the volume control pot and placed it in an ultrasonic bath with rubbing alcohol for about 15 minutes. This has fixed the static about a year now.....

After writing this I'll probably find that the static has returned... murphy's law.

[Jack H.]

Re: Mid year radio -volume knob static

Apples and oranges here, Duke...

The volume/tone/power controls are potentiometers. The reason for 'static' is EXACTLY what you described...'crude' built up on the windings of the variable resistor & its wiper contact arm in the pot assy.

These radios were built rather cheaply and the pot used were NOT sealed against the atmosphere. More expensive home entertainment systems spend a few pennies more on their components and generally incorporate sealed pots...

Cleaning IS a simple matter of squirting some electrical cleaner into the pot and turning it while the degreaser agent is still liquid turning to gas and evaporating. And, YES, places like Radio Shack sell TV Tuner cleaner in spray can form for exactly this application. In fact, some are doped with silicone (electrically inactive) to provide a lubricating effect.

But, on the issue of the radio's tuner, most of the el cheapo radios did use a variable capacitor as the heart of the tuning mechanism. However, Delco radios from this era did not. They bite the bullet and based their tuner on a multi-ganged variable inductor.

When you twist the station tuning knob, you're actually moving cylindrical ferrite core columns in/out of a series of inductor windings and thus altering the overall inductance of the tuner's 'heart'.

Since the cores slide inside air-gaps in each of the inductor windings, there's no physical contact. Hence, you don't get 'raspy' response from contact contamination...

Back to cleaning the tone/volume pots. To get physical access to spray the cleaner, the radio chassis needs to be removed from the car. Then, the chassis top cover comes off (a series of 1/4" hex head screws) to get inside.

The housing section of both pot assys will be readily evident...just follow the knob shafts back inside the chassis case. But, before you spray the pots with TV tuner, you're probably going to see dust/dirt EVERYWHERE inside the radio chassis!

I'd start by FIRST shooting the entire inside of the radio with printed circuit board cleaner to eliminate the surround dirt/dust. Hold the radio over a container like a waste can/trash barrel and LIBERALLY hose down the entire inside of the chassis letting the stray liquid cleaner run off carrying the dirt/dust with it into the waste receptical.

Let the chassis air dry. Now, you're ready to clean the pot assy's with TV Tuner cleaner. SOAK each pot housing with cleaner and turn its pot shaft fully (back and forth) while it's still wet. Let the residual cleaner evaporate and re-seal the chassis case & re-install in the vehicle.

If doing this on an earlier vacuum tube based radio, the tubes need to be FULLY off and cooled down before cleaning...

[Dan D.]

Re: Mid year radio -volume knob static

Volume and tone controls (known as 'Pots' - potentiometers) consist of a very thin film of deposited carbon. The carbon has high electrical resistance and when the control is rotated a wiper contact moves across the carbon film and the resistance at the point of the wiper adjusts the volume or tone level.

Static is caused when dirt gets onto the carbon and interfers with the electrical contact. These pots are not sealed and foreign airbound contaminents get in after time.

Spraying with just a cleaner will usually remove the contaiments, but will leave the carbon dry and the wiper will then eat through the thin carbon film, usually in a relatively short period of time. When this happens the pot is done. There are electronic products, designed for this application, that are both a cleaner and a lubricant. This is what you want to use.

If the problem is not corrected soon after it occurs, the abrasive dirt is dragged by the wiper and will eat through the carbon film. Again, when this happens the pot is all done.

There is also a third thing that can go wrong. Sometimes the carbon substrate will crack. This very small fisure will make and break contract and static occurs with any mechanical movement or vibration. Needless to say the pot is all done when this happens.

So first of all get a cleaner/lubricant that is designed for this. That will usually fix it. I don't know if Radio Shack or Digikey carry this stuff any more. They all used to. But don't wait too long. -Dan-

[Wayne M.]

Re: Mid year radio -volume knob static

The ultimate solution; NOS -- none for sale (just like Joe L.) at least until I've solved my own vol/static problems (like maybe in another 10 years ).

[Duke W.]

Re: Mid year radio -volume knob static

Apples and oranges here, Duke...

Yup! I was talking about the tuning knob... never mind...

Duke

[Gerard F.]

Re: Mid year radio -volume knob static

Gary,

Here's mine for a 67:



Over the years, I think I hit it one too many times with tuner cleaner to remove the static. Finally, about five years ago, I replaced it with an NOS Delco switch (the box). Has worked fine since.

Also replaced the main transistor at the time, cleaned the innards, and touched up all the solder connections. Sounds brand new with a replacement speaker with the little transformer.

I think 65-67 are the same radio. If you need the radio schematic, parts list and manual, email me.

[Jerry R.]

Re: Mid year radio -volume knob static

Dan, just a tip. If you ever face the crack in the carbon track problem, try this before throwing the control out.

Disassemble the control and locate the break (usually caused when the shaft is driven inwards by dropping or poor packing during shipping).

Reinforce/re-build the surface supporting the track (if its also broken).

Rejoin/re-align the track at the break and anchor it by use of small adhesive tacks at the non conductive edges of the track.

Rejoin the tracks electrically at the very edge of the carbon, where the wiper does not touch when moving, with a conductive bonding material. Make it tiny so as not to exaggerate the change in resistance during the wipers passing at the physical gap.

That method has successfully saved many controls.

For what it's worth...

[Carnell M.]

Re: Mid year radio -volume knob static

I used the contact spray method and it worked. But... now the volume switch doen't have a definite "stop" for off/on. It felt a little sticky at first and then finally there wasn't a stop. If you turn it all the way left the volume goes down normally but there's no "off" If I continue to the left it just continues until it's in the loud position. Any suggestions anyone??

[Jack H.]

Re: Mid year radio -volume knob static

Refer to the posted pictures. Observe the assy is a 3-stage unit ganged onto a common shaft.

One stage is the pot for the volume control. A second stage pot is the tone control. The third stage is a switch controlling power ON/OFF.

That third stage should LIMIT the shaft's rotation and stop you from being able to twist the knob past 360 degrees...