Tube Amps / Music Electronics
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|8/21/2000 8:46 PM|
Who knows about the conductive properties of mouse piss? Got in a Crate BX100 - pretty simple MOSFET output circuit - had a mouse nest in it (still don't know how the mouse got in) and the ouputs had shorted and blown the fuse. Removed the mickey motel, replaced the outputs, drivers, bias tranny, protection diodes and checked the resistors - fired it up - worked with my test speaker and them promply fried the IRFP140 when hooked to the cabinet speaker. OK, so maybe I got a bad device in the replaecments - rebuilt the section again (again checking resistors, etc) - burned it in w/o load for 5 hours, reset the bias - hooked up to my test speaker and ZAP goes the same MOSFET!!! (dang, darn, drat and damn!).
I dunno, have spent much time on the amp and much time on the horn with SLM tech support - so, without replacing the entire amp (one board with a "breakaway" output section) can anyone recommend some way to get rid of the rodent "golden shower?" Have flushed with water and methanol so far.
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|8/21/2000 10:19 PM|
well, the mouse pee is probably moslty water, salt and urea. All of which are pretty soluble in water.
salt= really soluble,
urea= soluble to about 8Molar.
Are you sure that mouse pee caused this? Are there any crystals dried between the tracks or something? It sounds like you are shorting the mosfet out, (you probably knew this)
maybe try some elbow grease if you rinse again. If water won't work, you could try a light solution of tide or something.
just a thought, is there some hair or something that is left under the board or anything?
|8/22/2000 2:08 AM|
Not sure of much actually except I've rebuilt the output section twice and it's died the same death three times. Yeah, there was some whitish residue on the board but I wiped it off before firing it up this time. Hell, I don't know, I do 5-10 SS output rebuilds/year and this is the first time this has happened in 20 years or so (and I know why it screwed up in the 1970s) and the unlikely seems to be what's left - want to speculate on conductive copper/lead/tin salts that uric acid could create and their actual conductivity?
|8/22/2000 3:13 AM|
usually, unless the crystals were perfectly grown over the traces, I wouldn't expect them to conduct much at all unless they were in solution of some kind.
I would start checking the stages before the power amp. Maybe the blowing MOSFET turned around and put some high voltage on the emitter of a transistor blowing it up. (or about 1*10^417 other possibilities, of which I have no idea)
|8/22/2000 12:45 PM|
Rebuilt everything up to and including the MOSFETs - anything that's DC coupled.
|8/22/2000 12:22 PM|
was it a grey mouse or a brown mouse
grey mouse pee sounds better IMHO
unique problem hope you get it fixed man!
|8/22/2000 1:06 PM|
Mouse was gone but our common rodents are either deer mice or white-footed voles - probably the latter which tend more toward the gray
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