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looking for help with a second hand amp i bought which seemed to be o.k. until i gigged with it. the fault is exhibited as this :- volume starts to fade out after about 20 mins of playing. have used a pre amp plugged into the effect return to discount possible preamp problem. Ran amp out of its case with no input but all controls on full (speaker connected)to check for over heating, mosfet heat sinks stayed cold,all high wattage resistors apart from 2 became quite hot (other 2 were cold?) any assistance or ideas would be greatly appreciated.
re the above: i have just spoken to the nice marshall people and they have sent me the curcuit diagrams to help. any other help would still be appreciated - i have no problem working thru the preamp but not so hot with power amp.
Hi I have this problem with Marshall amps in general.If the sound is just dropping in volume and not distorting it is the return socket on the loop.Just change both send and return sockets and it should do the trick.