After half an hour of use a loud consistent pitch , low frequency buzz
Proper solder, from what I've tested .
Mark Bass/ UK have "repaired" this before, changing the tweeter. Even the
owner knows this is ******** as he has a recording of the buzz from the main
speaker, before and after that "repair" .
I've heard it and if it was a conventional power supply I would have said it
was a loose main rail electrolytic or bridge rect and consequental 150 Hz
buzz (uk mains of 50 Hz).
I've heard this recording but have not been able to measure the frequency ,
so may not be 150 Hz.
Of course now its out of the cab and opened out on the bench, no problem
with it, with dummy load, directed hot air over PS/PA and PREA and
"twizzling"/ targetted wrenching. Not brought out the big-gun yet, engraving
tool with nylon active end , and headphones (because of horrendous noise)
monitoring of output.
But as a thought experiment. What sort of fault in a SMPS amp could produce
such a 150 Hz buzz? Anyone ever known a problem with the HV DC to the SMPS
producing interference on the PA rails?
When its occured with the owner , no amount of kicking the cab would make it
stop or even change character. I will have to check with him if the buzz is
total or buzz over the guitar output as recording by owner was obviously not
playing at the time. And try and get a sound file / copy of his recording to
measure the f
ps
the ident of the SMPS driver is ground off , as per usual , it would seem