Carlsbro PM15 amp, 2001, intermittant loud bangs
 

Dual purpose 200W PA head or as used by some pub rockers,
a foldback monitor for 1000W system.
Reported occasional loud bangs and pops without any signal
input, otherwise no distortion. Of course I powered
up and with any amount of banging of cabinet no induced problem.
Took apart and powered up with twizzle stick biro barrel and serious
bangs and whistles can be induced by tapping in area
of electrolytics C1 (4.7uF,63V )and C3 (47uF,63V) and
2 small signal MPSA92 all at input
from pre-amp. C1 probably AC coupling from pre-amp and
C3 local DC rail decoupler. Is this a stock fault with one of these
components ? Otherwise no dodgy looking fuses, spade terminals
hotspots or suspected dry joints anywhere.

Diverse Devices, Southampton, England
electronic hints and repair briefs
http://home.graffiti.net/diverse

I cannot believe that since this jackass cannot set his internal date, that
Im stuck with this stupid posting for another 3 months at the top of my
newsgroups
"N Cook" wrote in message
...
Dual purpose 200W PA head or as used by some pub rockers,
a foldback monitor for 1000W system.
Reported occasional loud bangs and pops without any signal
input, otherwise no distortion. Of course I powered
up and with any amount of banging of cabinet no induced problem.
Took apart and powered up with twizzle stick biro barrel and serious
bangs and whistles can be induced by tapping in area
of electrolytics C1 (4.7uF,63V )and C3 (47uF,63V) and
2 small signal MPSA92 all at input
from pre-amp. C1 probably AC coupling from pre-amp and
C3 local DC rail decoupler. Is this a stock fault with one of these
components ? Otherwise no dodgy looking fuses, spade terminals
hotspots or suspected dry joints anywhere.

Diverse Devices, Southampton, England
electronic hints and repair briefs
http://home.graffiti.net/diverse