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birdyman 4th June 2010 11:10 PM

Rotel RB 1080 Glue Problem
I have been working on Rotel RB 1080 with bad right channel and white noise.
I found bad rust parts ( resistors and diodes next to electrolytic caps). I was wondering what caused rusting of parts and eventual opening of leads. All of rusted parts are covered by contact cement( glue??) to stick the big caps to board. Contact cements are discolored to black(normally yellow) on my Rotel rb 1080 amp boards(1000uf x4, Black Gate x2) and balanced input board (Black Gate 470uf x 2). Discolored glue tasted acidic in my tongue. I originally thought leaky caps. But there are nothing wrong with caps associated with contact cements. I removed all caps and cleaned all contact cements and washed with Simple Green and water. I also replaced rusted zener and resistors. My amp is working again.

I am not sure of chemical reaction of or cause of contact cement discoloration. May be some one can chime in for this.

bob91343 5th June 2010 12:07 AM

Probably a poor choice of glue at the factory, combined with a humid, polluted environment. I wouldn't glue the parts back unless they seem shaky. And I won't comment on Simple Green; maybe it's just soap so at least rinse afterward.

homemodder 5th June 2010 12:07 AM

Ive worked on many Rotels, never seen this before, but if the caps arent leaky then the only thing I can think of is factory fault, maybe they dropped some solvent or something in there during manufacturing.

birdyman 5th June 2010 07:16 PM

If you see black glue around big caps on the amp or balanced input boards, you have same problem like mine. I think they used either wrong kind of glue or bad batch of glues that corrode metals.

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