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
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