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Posted on Monday, August 22, 2005 - 05:08 pm:   

I have a hd130reverb head...chassis 2275-130...with pi tube........I just retubed the amp and deox'd it....i get a signal noise when the reveb is turned on....checked the tank and everything is mint.....Im thinking it maybe in one of the ic's.......they are nte 937's...i think there are 7 of them on the preamp board...looking at the schematic it would appear only two actually are tied in to the reverb....my question is which two?.Im thinking of replacing them to help with the noise problem?
mike kaus
Posted on Sunday, January 22, 2006 - 03:27 pm:   

I don't see nte937's anywhere on the schem that I have of PI type amps. I have to assume that they have been replaced. I only show LM307 op amps in the chain. One of them could be noisy I suppose. IC#5 and 6 are in the reverb stream and they pick up their signal from the wiper of the channel two treble control. Clean your treble pot and then check 5 and 6.