RD50 crossover distortion

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Author Message   Kent Fossgreen Posted on Tuesday, June 08, 2004 - 01:27 pm:    Just replaced the SJE1692 transistors with TIP31 in an RD50 running Boogie relabeled Sovtek 5881WXT, which now exhibits obnoxious crossover notch distortion. I've seen references in other threads to this circuit as self biasing, but it certainly isn't acting that way with the replacement transistors. Any suggestions for adding a trimpot to this circuit or potential culprits that could lead to lack of self adjustment? I've checked all the associated components and they're all well within tolerance. Thanks for any info!   Terry Posted on Friday, June 11, 2004 - 08:47 am:    Hi Use 2N6488 transistors. The tip31 may be the problem.   Kenneth L Fox Posted on Wednesday, June 16, 2004 - 10:45 pm:    I am fixing a second one for a friend tonight. His other one did the same a year or so ago. The 30 volt zener went out, bias went from 30volts to 4 volts! That is Diode D9, 1N4751A or NTE5084A (1 watt at 30volts). It is located near the top left corner of the board (front being towards the front of the amp). If original, is is a glass diode (amber colored)