stillplaying1965

OK, thanks, Agedhorse

i'll take it up from here

most likely it will be the "mothballs-solution" at first

maybe later I might try to salvage the power-amp and couple it to some power-supply,possibly in another housing

or, if I get really into electronics (or find someone around who is), try to fix the power-supply

for now I will get my Eden E300T out

chiropractor, here I come 😉

kind regards

Peter

Belgium

agedhorse

in your professional opinion, does the squealing tell you anything

and that it has occured in al least two cases

it seems to emerge from the power supply, not the power amp, as if cooling-fin is pushed into resonace

maybe some insight here might be usefull if I choose to contact my local guitar/amp tech

he is kind of an electronics wizzard, not sure if he is up-to-date with SMPS'

thanks, agedhorse

I did not yet try, as the squealing is rather scary, to test if pre-amp out delivers signal or if power amp can be run from an external signal

FWIW, my observations:

"protect" led is lit

"signal" led flashes when plucking (hard) a plugge-in bass

all other leds are lit (or can be when pad is pushed in)

cooling fan is running

so I guess power supply is supplying some of its voltages

so I guess the problem lies with the main voltage rail

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

dear Alex

did ever you find a solution to the squealing problem on your GenzBenz NeoPak 3.5?

mine has the same problem, also after a long (Covid)standstill

it also goes into the Protect-mode

squeals seem to emerge from the power supply module, as if the switching transistors and/or the power diodes make the cooling fin resonate

tried cleaning and bridging the send/return and replacing the pre-amp tube, to no avail

I kind of worry, as GenzBenz used to look upon the power supply as non-reparable

and also GenzBenz went out of business

this also makes me worry about all modern amps with a switching power supply (especially the resonant types) and about the most recent "full-digital" types

what would force me to go back to the weighty classic amps

kind regards

Peter

Belgium