Fungus in Guitar Amp?

[DerEber]

Hello friends,

I got an Engl R. Blackmore Amp for repair. It had some HF-Pickup or random oscilation problems and when I opened it up
I discovered some white dirt layering on the board.

What is it? Is it fungus or something else leaking from bad glue?
I had a hard time to rub it away with Isopropanol. Didn´t manage to clean it fully. But the amp works fine now.
Well I suppose to get problems again.

best greetings,
Stephan

 

[pucho812]

not sure what it is but I would take chances and breath any of it in. I have seem similar before but that was with gear that was left outside being exposed to the elements.

 

[okgb]

Curious the sort of arching pattern that it makes

 

[tommypiper]

Could it be crystals from an incomplete or botched acid bath or cleaning product used during the PCB fabrication?  It might not have appeared right away, but as the solvent aged or was exposed to oxygen and humidity, or whatever, it developed the crystals…  There may be some electrical sensitivity which explains the arching character which appears to link the solder joints, which would be possible if it were some kind of crystal formation… it would form crystals aligned with polarity, just as man-made crystals do during production of synthetic gemstone materials…   

But it does not appear to be fungus.  Fungus would clean easily, me thinks. 

It looks like solvent residue and/or crystallization to me.

 

[Kingston]

On the bright side you got a magnetic field tomography of the circuit implementation, which would be incredibly expensive with current technology or would would take a significant chunk of processing power to simulate with this precision.

 

[zebra50]

Smoke machine gunk? I had a very sticky PA amp in for service that had been next to a smoke machine for too long.

 

[Andy Peters]

Hello friends,

I got an Engl R. Blackmore Amp for repair. It had some HF-Pickup or random oscilation problems and when I opened it up
I discovered some white dirt layering on the board.
What is it? Is it fungus or something else leaking from bad glue?
I had a hard time to rub it away with Isopropanol. Didn´t manage to clean it fully. But the amp works fine now.
Well I suppose to get problems again.

The manufacturer did a poor job of cleaning the boards after stuffing. Use a toothbrush and scrub with some proper cleaning agent (not alcohol), then rinse with distilled/de-ionized water and dry.

-a

 

[DerEber]

Well no smok machine over here.
But I now belive that it could be indeed some kind of acid residue. Reminds me of my times in the photo-lab.
Anyway maybe I try to make some fungus test just for fun. Also I will try to call the manufacturer.
So now I´m open to any simple idea what to use as an cleaning agent.
Alcohol will for sure feed any fungus, but if it is acid residue? I´d better use soap like stuff?

best greetings,
Stephan

 

[pucho812]

come to think of it I saw a similar thing in a unit that had an electrolytic which was disintegrated. That stuff looks like some of the material used inside the cap.

 

[L´Andratté]

http://ekadek.com/wp-content/uploads/2012/08/jansen2.jpg

 

[bruce0]

Very cool.

I love a puzzle, here is  a theory.

I can't really go for the acid bath theory because the coating on the board seems intact and undisturbed by the arc's of material.  But the arc's are cool. 

Do they all go in the same direction in the case when the PCB's are mounted? (if so, environmental cause would make sense).
They do seem to originate from the solder joints, and corners.

I think they cleaned the flux off in a bath and used air jets to spray off the residue.  incompletely.  The flux somehow crystalized, changed or attracted some dust or other environmental foreign matter, the result of which was conductive enough to cause a problem. 

The arc shapes are then the residual effect of incomplete cleaning and the arcs are a flow pattern of the flux remover.

 

[CJ]

when they wave solder a board, it goes by a "fluxer" first, then it goes by the molten solder, then it gets air blown over it to cool it off,

a fluxer is a tank with flux in it and at the bottom of the tank is a bubble maker like you have in your fish tank, the bubbles create a layer of flux foam at the top of the tank so that as the board passes thru the foam, it gets a light coat of flux, this helps the molten solder to stick to the leads and traces,

if the ir pressure to this bubble maker is a bit high, you get excess foaming of the flux, this means the board gets coated with flux a bit too much, which means that all the flux does not get vaporized by the molten solder,

so the white stuff you see is just unburned flux, very common in the circuit board industry and nothing to worry about as most types of flux have a high dialectic constant which means that there is no paths of conduction created,

it can also be cause by not having enough solder in the tank which means that there is a bigger gap between the board and the hot solder, or a partially clogged solder pump, or solder that is too cool, setting up those machines to run perfectly is an art, and the molten solder fumes and flux fumes are not good to breathe all day,

HP might clean off this residue, but Samsung might leave it on to save labor,

i would tell Engle to Flux Off!  i bet Ritchie has already,

you can see a board getting fluxxed right here>

the white smoke is the flux vapor, which is what is stuck to your board,

http://www.youtube.com/watch?v=inHzaJIE7-4

 

[bruce0]

cool CJ... Never saw that in operation before.

So are the arcs remnants of bubbles?
Or remnants of ripples in the surface of the wave soldering machine that didn't properly vaporize the solder?
Or something else?

 

[DerEber]

I talked to the manufacture and got in contact to a realy helpfull guy and he stated that it was indeed a problem caused by the flux machine. He sad that this is causing only optical problems....In fact cleaning did not solve the problem. I will get the amp back next week..... propably its as so often simply a worn out tube.

best greetings Stephan