zephead Posted July 21, 2018 Share Posted July 21, 2018 Hi guys, I have a vintage 80s Trace AH250 GP11 head which keeps cutting out under load. The signal starts disappearing and the green power indicator in the front panel starts to flicker before cutting out completely. However the green power on switch at the rear of the amp stays illuminated throughout. Frustratingly if I give the top of the amp a good thump it starts working again for a short time before breaking down again. I'm guessing it's bad earth somewhere - anyone got any ideas? Quote Link to comment Share on other sites More sharing options...
King Tut Posted July 21, 2018 Share Posted July 21, 2018 Try putting a jack lead between the fx send and return sockets. Sometimes these need replacing. Quote Link to comment Share on other sites More sharing options...
zephead Posted July 21, 2018 Author Share Posted July 21, 2018 39 minutes ago, King Tut said: Try putting a jack lead between the fx send and return sockets. Sometimes these need replacing. Will give it a go - thanks! 1 Quote Link to comment Share on other sites More sharing options...
DrDrill Posted July 22, 2018 Share Posted July 22, 2018 Also with the power off. Take your lead and push the jack plug in and out of ALL the sockets on the amp a few times to clean them. Years ago I had an intermittent fault on mine for months that no one could fix and i discovered this snippet on t’interweb somewhere and i’ve had no problems since. Quote Link to comment Share on other sites More sharing options...
MoonBassAlpha Posted July 26, 2018 Share Posted July 26, 2018 Good suggestions above, could also be a dry joint somewhere internally which banging it restores temporarily. May need a good going over with the soldering iron (or get someone to do it for you, preferably with experience with this kind of thing). First suspects would be larger components that are more likely to vibrate (resonate) at the lower (bass) frequencies, like psu caps, and large resistors which have been stood off the pcb etc. Quote Link to comment Share on other sites More sharing options...
zephead Posted July 28, 2018 Author Share Posted July 28, 2018 Thanks for the suggestions! The cutting out seems to have cured itself for the moment but now there is an annoying crackle that is driving me nuts! I have discovered this only occurs when the EQ switch is in the on position - I tried cleaning it with switch cleaner to no avail, does it need replacing or is there another reason that might be causing the problem? Quote Link to comment Share on other sites More sharing options...
barkin Posted July 29, 2018 Share Posted July 29, 2018 One of the EQ sliders? (Not in circuit unless the EQ switch is on) ?? Quote Link to comment Share on other sites More sharing options...
zephead Posted July 29, 2018 Author Share Posted July 29, 2018 3 hours ago, barkin said: One of the EQ sliders? (Not in circuit unless the EQ switch is on) ?? I think the problem is under load - when the eq switch is on there is a big surge in volume so now reckon it could be anything! Might just have to go round the pcb with a solder iron...... Quote Link to comment Share on other sites More sharing options...
zephead Posted August 14, 2018 Author Share Posted August 14, 2018 A wizz round the PCB with a solder iron together with copious amounts of switch cleaner seem to have done the trick - thanks for the advice! 1 Quote Link to comment Share on other sites More sharing options...
geoff90guitar Posted August 15, 2018 Share Posted August 15, 2018 Could be capacitor not doing its job. You could fiddle all day and it can still let you down. Take it to an amp repairer, with a scope -probably works for the music shop. Normal charge £40. May even lubricate the fan if decent. Quote Link to comment Share on other sites More sharing options...
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