TECH GURU's out there, how to clean Circuit Board?

Looks like something has spilled onto the Circuit board. Older Rotel amp, there some greasy stuff and cat hair all over the internal board, very dirty and grimy.....

How do I clean this up, works perfectly but I believe its not a healthy thing, I am a tech oriented guy so I need instructions, like what can I use to clean, solution or anything? brush and what should I avoid doing.

Thanks for your help
well, 1st unplug from the wall. ensure that the power supply caps are discharged before you stick your hand inside the chassis.
best would be if you can disassemble the portion of the amp that needs cleaning. this way you can conveniently handle the PCB outside the chassis.
use alcohol - the 90% type you can get at a drug store - to clean the mess.
Chemtronix makes a can of a fluid called "Flux-Off" that is water soluble. You can spray this on the PCB & then remove the residue w/ alcohol.
Hooe that this helps.
Thank you very much, the Chemtronis and the Alcohol,they wont damaga the board correct? I am thinking I can remove any parts from the board so I might use a small brush and dip and clean kind a thing, would that work?

Thank you

If it aint broke ......

I would take the lid off, go outside and use a can of compressed air to blast off the excess dust and hair. The only reason I would do this is to ensure good air circulation inside the amp and prevent fires. IF you're very careful you could use a vacuum cleaner.

I would not clean the PCB, certainly not with 90% alcohol (the other 10% is water). If the PCB is working then it doesn't need cleaning.

perhaps you did not read Rapogee's original post correctly. I cut & pasted here: "Older Rotel amp, there some greasy stuff and cat hair all over the internal board, very dirty and grimy....."

greasy stuff will not be blasted off by compressed air. In fact, if the greasy stuff is at all mobile, compressed air will splatter it farther & wider creating an even bigger issue in other parts of the amp (that perhaps do not have issues so far)!

OTOH, Seandtaylor99, does bring up a good issue that the 90% alcohol does have 10% water in it. I can tell you that I have cleaned PCBs with this 90% alcohol before BUT..........I did use a hair-dryer to dry the PCB + I let the PCB air dry for atleast 24 hrs before I switched on the circuit.
Good catch Seandtaylor99! Otherwise, I would not have mentioned my hair-dryer routine! ;-)

Rapogee: the Chemtronix Flux-Off will not harm the PCB. I've used that chemical routinely to remove sticky/guey flux paste & fluid from PCBs. No harm has ever been done to the PCB.
Like I said above the alcohol will not harm the PCB either. However, make doubly sure that you dry the PCB (make that water evaporate) before you plug the PCB back into the Rotel amp.
Cleaning the pcb will be beneficial because there can be current leakage between parts, depending on the nature of the spilled matter (type and amount). Also, if you ever want to sell the unit, you would not want to sell someone a component in such condition. 99% pure alcohol can be easily obtained from most electronics stores, along with necessary brushes, swabs, etc.
A electrical parts cleaner CFC free will work wonders. It will be expensive but they have several types that leave no residue. Almost any hardware store like ACE will have this. If you cannot find any go online and search for electical cleaners. There are cleaners that will harm PCBs but most will not. Read the can before you use and most will require PLENTY of OPEN AIR so that you dont become sick from the fumes.
Concerning the use of Flux-Off: be very careful where you spray this as it will eat away plastic surfaces very quickly. Keep the spray focused to the PCB area needing cleaning only.
Be careful about alcohol, and any other cleaning agents.
In building inertial guidance systems for ballistic missiles we found that the best fluid for cleaning circuit parts is Freon. We used it for decades. Concern for the Ozone layer forced us to abandon Freon except for a few very critical processes.

After a research project lasting several years it was determined that a Citrus-based cleaner was next best. Since we discovered this many citrus-based cleaners for general home use have appeared on the market. I do not know if these are the same as what we now use for circuitry.

Your best bet is to find out what product is now sold specifically as a Freon substitute for electronic part cleaning.
Bombaywalla .. I think you did not read the original post correctly. The amp is stated to be in working condition.

When electronics is working I don't go pouring liquids onto the PCB. Not water. Not alcohol, not even electronics cleaner (as some PCB cleaners will damage some components).

Like I said, if it isn't broken do not "fix" it.
Eldartford ... are you still sticking with your defination of


as ... Pratical Range Against Target
my good man, I did read Rapogee's original post very well. Yes, I noted that it "works perfectly but I believe its not a healthy thing".
even if the gear is working perfectly, electronics & "some greasy stuff and cat hair all over the internal board" are 2 things that do not go together! a dirty PCB is a disaster waiting to happen especially in a power amp (a high gain & large signal piece of gear). it should/must be cleaned up otherwise failure over the longer term is almost certain.
It looks like we disagree. OK, so be it!
No need to resort to patronizing language. Non conductive gunk on a PCB is almost certainly NOT a failure waiting to happen. If the gunk were likely to cause a failure it would probably have done so already. Using any cleaning agent risks doing more damage than the "gunk" that you're trying to remove. If you are willing to risk damaging components on the PCB to make it clean go right ahead and clean it. I would leave it alone.

Excessive dust and hair impedes airflow and is best removed to prevent any chance of overheating (though even this, I feel, is very unlikely).


* I know your coordinates!
Thank you very much guys, very helpful.
Just to clarify, I tried the micro vacum and compressed air and that did not work. There is hair and dirt still sticking, I bought this used, amp is around 6 years old so not ancient but used by some dirty bunch I believe.

I can get the grime off with slight damp cloth, and cleaned out what I could and let it there overnight and turned it on and used, perfect but I was trying to get the rest of the dirt off, I believe a small brush with the Chemtronis might work if done with care.

Well I rather leave it the way it is and use but its eating me, I am anal about my gear and I rather clean it up to make sure its well, thanks again guys

Last question,

I believe I can spray this carefuly over the board where the grime is and clean gently? It wont harm the parts that are presently on correct?

This might be better maybe? Anyone? See link below


Maybe better to use q-tips with cleaner, so that you don't have to spray directly onto the board, and risk stuff disolving and being carried to even less accessible areas. I have done this to clean excessive flux off parts I was repairing in the past.

This stuff would probably do it if not used too liberally.
There are several products made to clean circuits. If it weren't pouring down raining outside I'd go out to my car and get one so I could read the label to you. Find a product made for contact cleaning, get a small stiff brush, and go at it gently. I like to use acid brushes (that's what I call them). They are about six inches long with fairly soft bristles. I cut the bristles to about half their length for firmer brush.
I do this all the time. If the board is removable, take it out and saturate the offensive area and brush if needed.
This is not a problem if the proper product is used. Be careful because as one of the previous posters pointed out, some can harm plastics. Good luck and let us know the results.
Timrhu...Contact cleaner is for contacts! Some electronic parts will not take kindly to such treatment. (Don't ask how I know). I know Freon is safe, but you can't get it. I know that a safe Freon replacement cleaning fluid exists, and I wish I could give you the name of the stuff. Do some research.
>> 03-09-06: Rapogee
>> Thank you very much guys, very helpful.
>> Just to clarify, I tried the micro vacum and compressed
>> air and that did not work. There is hair and dirt still
>> sticking,

Rapogee, thanks for the feedback! I didn't think that compressed air would work on the greasy grime.

The MG Chemicals Flux Remover looks very much like the Chemtronix stuff that I recommended. FYI: the Chemtronix stuff is an industrial product that is used in my engineering lab here where we populate PCBs to test out some of our ICs that go into cellphones. My recommendation was *not* a butt-pull - we use this stuff nearly daily to get guey stuff off our PCBs esp things like flux paste/fluid. Like the pix on MG Chemicals webpage, the Chemtronix can comes w/ that red colour straw nozzle that allows us to point the fluid more-or-less exactly where the guey stuff is. We have *not* ruined any PCBs so far & we have been in operation for over 10 years!

I was thinking of this last eveing & here is another idea: how about using "Goo-Gone"? I have used it to remove several sticky things (like stickers on CD jewel cases, airport security stickers on suitcases) but never on a PCB so far. This Goo-Gone is citrus-based (atleast the one that I have) & it does a great job of removing guey stuff. I've used some alcohol post Goo-Gone to get do the final clean-up. In your case, use a hair-dryer to dry the PCB thoroughly + let it air dry for 24 hrs before turning on the amp.
IMHO, this should really do the job for you. FWIW.
Eldartford, I used the name contact cleaner as a generic name, my mistake. I brought the can in and here is the info. The brand is Chemsearch, the can says Lexite PS, Electrical Cleaner Dergreaser, the label states "safe on plastic, rubber and plastic - no residue - no disassembly required." I have used this on circuit boards repeatedly to remove residue from spills, leaky caps and rodent urine and fecal matter (disgusting). This stuff works pretty well without harming boards. Given time it may cause some deterioration but I haven't noticed it. The residue is probably more harmful than the chemical.
Now I recommend first cleaning the affected area with denatured alcohol and a brush and then spraying the cleaner. That's how I do it. Good luck.
Thank you everyone, Bombaywalla and all of you out there!
Very knowledgeble people and this is why I like forums such as these, very educational and helpful.

I used all your advise, paid $10 for the unlta wash from Radio Shack, $4 for brushes from the dollar store, cut the brshes up to enhance the stiffness and control .5 inch sprayed over the brush and cleaned process, never sprayed directly to the board only on some empty areas than needed.
Used a little alcohol or some areas with cotton swab and too my time and cleaned it up good. WORKED!
Images enclosed:

Believe me the board was originally brown in colour with dirt all over.... like the lable shown with the serial board #####, NOW ITS GREEN as original... Thank you very much. First 2 images shows cleaned board, last shows the cleaner I used, I also used rubbing alcohol or certain stuborn areas very little and with caution.
Looks good as new in pics. Kudos on a job well done!
thanks again on the feedback, Rapogee. looks like a job well done by yourself!