crackling in stereo - electronics cleaner inside?

[JHZR2]

Hi,

My 91 BMW 318i has its original tape deck. Works fine more or less, except one thing.

When I turn the volume, I get crackling in the speakers at different volume levels. I think some may be one side or the other, but Im pretty sure that for the most part it occurs in both sides.

I assume the volume knob turns some kind of potentiostat that has some amount of corrosion on it.

If I use something like CRC electronics cleaner, spray it in/on there, any chance that Ill help get rid of it?

While the car is a great driver, and the drivetrain will probably be good indefinitely, with some rust, etc., Im not sure it is smart to make a big outlay to replace with another OE headunit (and aftermarket ones are really ugly so Ill never do that).

What's the best way to go about this?

Thanks!

 

[Kestas]

Over time, potentiostats develop a layer of smut that precludes good electrical contact. This intermittent contact results in the "crackling" sound.

In the old days, a freon spray was used - excellent solvent, washed away the smut and flashed off quickly. Unfortunately, the freon ban put a stop to it, though there are other environmentally friendly sprays.

One trick I used, taught to me by 30 years ago by a guy who serviced my electron microscopes and was also a collector of old radios, was to do the following:

- Fill a washtub with a solution of [censored]-n-Span with warm water. The trick is to use a non-abrasive, non-chlorinated detergent.
- Completely immerse the radio chassis into the solution.
- Operate all the knobs to clean off the smut.
- When finished, drain the detergent solution and immerse in clean warm water to rinse off the detergent.
- Dry the unit by shaking and blotting as much as you can, followed by drying in the oven at low heat (150°F max).

This process not only cleans the smut from the contacts, but also cleans the dust from the chassis board. Sometimes the dust can act as minishorts on the chassis.

I've successfully done two radio chassis this way - one with a tape deck in my 91 Tracer, the other on the AM/FM radio in my 71 Cutlass 25 years ago, which still works today, crackle-free.

Or a quick way is to squirt alcohol into the potentiostat and work the knob to clean it.

 

[Jimmy9190]

The volume knob may have worn-out internal contacts that are causing the noise. You are correct about the knob turning a potentiometer to control the volume but I believe it is a sealed unit. CRC may or may not help. Your best bet would be to find a good independent car audio shop that has a repair tech who can fix it for you. If you can not find one locally you could ask around at a few car dealerships to find out who they use, chances are they can refer you out to a good repair shop. If you have an anti-theft radio with the flashing red LED on the front, be sure you have your anti-theft code written down before they remove your radio.

 

[JHZR2]

wow, the washing method is scary, but worth a shot...

It has an LCD, should it make a difference?

 

[Kestas]

It may be somewhat risky, but I believe all electrical components today are waterproof. Nobody uses paper capacitors anymore. I'm not sure how the LCD plays into this.

I just put that method out there because sometimes it makes sense to do it that way. Honestly, you may be best off squirting alcohol in there.

 

[Errtt]

The volume pot may need cleaning - I use products called Deoxit.
The D-5 spray normally for getting the oxidized contacts. G-5 for gold contacts, and for sliders, D-5 and follow up with F-5 FaderLube.
I buy the 5oz cans (locally @ Fry's) because of all the audio gear I have - vintage-modern / receivers, amps, preamps, phono stages... you name it. At the moment, I'm listening to a turntable > tube RIAA stage > custom built tube amp >> Klipsch Forte's.
Yesterday I cleaned up a crunchy sounding Sansui Quad receivers (a few new caps, adjusted bias etc - and cleaned all the pots with Deoxit to include all connections on the back.
It's now made my Caigs - I think @ "Audio Karma" forum in the "DIY" section (maybe Vintage ssection), there is a how to cleaning audio gear pots. Although, it's mostly home audio, I believe there is a auto section to.
Anyway, it's a lasting product unlike some other contact cleaners, but there are also others that do probably just as good - just saying I use Deoxit.

 

[Errtt]

^^^^^ yes PCB / printed circuit boards can & have been washed - just need to know how to do it properly. Gets done more than most would think with some old vintage gear - I don't do it myself (have other ways) but I know a few who do.

 

[VK56VD]

Look into Blaupunkt head unit's. It will sound much cleaner than your current unit and may match your European dash a little better than other aftermarket brands.

 

[brianl703]

2nd the Deoxit, it works well. Another option is to look at heavy duty truck stereos, they are usually not flashy. Crutchfield carries a few made by Jensen. Review comments say that they like the non-flashy appearance.

 

[AdRock]

One thing you can do is turn the volume knob back and forth quickly a bunch of times with the unit off. Sometimes this will knock the junk off and keep it working for a while longer.

Working with PA equipment like I do I have to do this every once in a while to some pots that don't get moved very often. It usually works for long enough to get a new pot to put in.

Personally, it's just a tape deck, not a 1k amp. I'd just replace it.

 

[sleddriver]

+3 on Deoxit Red if it's a metal pot/slider. Use Cailube MCL if it's conductive plastic or carbon. If it's a sealed pot, you'll probably have to replace it.

 

[andyd]

A few of my 80s BMWs had a crackly on/off/ volume switch. I used old school tuner cleaner on it. The wiper on the pot gets dirty. On one of them, I spent a few hours taking the radio apart until I was able to undo the tabs on the pot case , and get to the wiper. IIRC , I was amazed it worked , but it did.

When I worked in the shipyard, one of the divers dropped a walky talky into salt water. It was immediately dunked into a bucket of fresh water. Then allowed to dry out. As I remember, it worked.