Cleaning a dirty stereo PC board

[gary7]

Picked up a distressed Pioneer A-717 integrated amp. Was very dirty. Had broken pot shafts on bass & treble. Dirty, dusty inside. Vacuumed inside best I could & deoxed controls. Fired it up and plays fine. But the main PC broad is still covered with a layer of crap. Should I leave it or is there a safe way to flush it out? I have a can of contact cleaner, would it cause more harm than good? It is actually where it would drain out of the unit if I stand it on it's side.

 

[Blue Shadow]

Flood it with contact cleaner while on edge and use a paint brush to loosen the crap and rinse a couple times. Good way to use up some contact cleaner as in a spray can you are gonna need a good bit. I use LPS Electro Clean 140°, a liquid and a paintbrush. Stuff comes clean. I rinse with a spray of isopropyl alcohol which dries fast. Then wait a day or two and see what is up.

 

[Watthour]

Or you could disassemble the unit and wash it. Hot water and soap, and a stiff brush.

 

[SoCal Sam]

Compressed air and brush to get rid of caked on dirt. Then residue free contact cleaner will be fine. Spray in the shade or when it is cool, if the cleaner evaporates too fast, it will freeze and form frost which is not good.

 

[willyrover]

Set the board or the whole unit vertical over a pan with some warm water and some dish detergent. Use some paintbrushes to lift the grime and let it run off into the tray. I use a syringe to rinse - the kind you get with inkjet refill kits. First distilled water, then alcohol. Dry with a hairdryer or heatgun.

 

[Blue Shadow]

Set the board or the whole unit vertical over a pan with some warm water and some dish detergent. Use some paintbrushes to lift the grime and let it run off into the tray. I use a syringe to rinse - the kind you get with inkjet refill kits. First distilled water, then alcohol. Dry with a hairdryer or heatgun.

Oh here we go...put em in the dishwasher?!!! No really some people do?!!!

Actually nothing wrong with what you did as that is what Tektronix did to stuff coming in for work back in the day. Wash it in a lab setting and put it in a very low oven overnight.

 

[richs8778]

View attachment 1249715 View attachment 1249716 View attachment 1249717

Set the board or the whole unit vertical over a pan with some warm water and some dish detergent. Use some paintbrushes to lift the grime and let it run off into the tray. I use a syringe to rinse - the kind you get with inkjet refill kits. First distilled water, then alcohol. Dry with a hairdryer or heatgun.

hot soapy water & brush, rinse & set out in the sun to dry for 2-3 hours, works great

 

[ryuuoh]

Hot soapy water, in the first degree:

sorry, I couldn't resist

 

[Mayank]

I have always relied on a gentle bath in diluted Simple Green - it isn't as harsh as commercial dish detergents from the kitchen. Works really well on removing the corrosive electrolyte from aged leaky capacitors and older solder flux. For more stubborn PCBs, I have also used ultrasonic cleaners.

Here is how one dirty PCB looks which was cleaned recently.



IMPORTANT: remember to remove/desolder potentiometers, relays and switches before washing the PCB!

Good luck
Mayank

 

[bryans12v]

I would start with the vacuum and long bristled paint brush to loosen the caked on stuff. using compressed air right off the bat will blow dust to other areas where you don't want it.

 

[merlynski]

My SX-780 was just about as dirty. I removed the covers, set it on end on a stand outside, blew it out with compressed air, then sprayed/soaked it with straight Simple Green. Lots of crud came off that way. Then I rinsed it with low pressure tap water, being careful to NOT spray against the backs of the meters. Another treatments of Simple Green and gentle application of a nylon paint brush to loosen and brush away what was left. Another gentle rinse with water, then blow it out with compressed air. Followed that with a rinse of denatured alcohol (cheaper than isopropol), then more compressed air. I was careful not to get too close with the air nozzle so I did not blast any parts off the board or chassis. There was a white residue left on the bottom of the PCB, so a light scrubbing of dilute simple green on the paint brush,, water rinse, then alcohol rinse again removed it. I did use a non-residue contact cleaner on the tuner's variable cap for the last cleaning step. Set it near a 60 watt light bulb for a couple of days to dry. Was much easier than I expected.
Before cleaning photos:


After cleaning photos:


Next step is De-Oxit controls and replace main power supply caps.

 

[ryuuoh]

The vari-cap might start making noise after the cleaning. Deoxit on a cotton swab applied to the contact leaf springs is a good idea. Fixed a noisy TU-717 that way.

 

[merlynski]

The vari-cap might start making noise after the cleaning. Deoxit on a cotton swab applied to the contact leaf springs is a good idea. Fixed a noisy TU-717 that way.

Yup, that's the plan .