very much thanks, Agedhorse
I had seen your name around on talkbass fora on GenzBenz products but I had assumed - judging on your pseudoname and on the long-ago dating - that you had retired
nice to see that you are the factory service guy and that there is still support, althought probably not do-able from/in Belgium
bought my NeoPak3.5 some 6 years ago from a Brussels shop going out of business (at very discount price), where it had been lingering on the shelf for some 10 years
chose it over a SWR350X (also at discount) for being much more rock-sounding
used it some 3 years, then came Covid19 and it stayed dormant for 2 years
and now it has this squealing thing
I had hoped stillplayin1975 had come up with a simple solution then
I just finished repairing a GallienKrueger MB150E power supply
had dropped it and one of the legs of a power diode had sheared off
easy to repare - but hard to find the culpritt
although this experience learned me most of my power supply "understanding"
I had hoped on a comparable simple fix for the NeoPak
I am a brewing, not an electronics engineer, so I wont venture into dangerous and complex electronics
seeing that the power amp is classical transistorized I am thinking first at replacing the SMPS by some other PS
unless I could fix the power supply (say soldering some new TO220 transistors or diodes, not fixing the steering circuits)
or putting the thing into the mothballs and replacing by some other lightweight bass amp
although this experience has left me doubtfully about anything switching power (supplies and digital amps)
kind regards
Peter
Belgium