fatboy Posted November 23, 2007 Report Share Posted November 23, 2007 Having some problems with my second hand Marshall avt275 mk 1first during band practice it died completely as a result of unplugging one of the speakers to used it for something else (bad idea, i know), i replaced the fuse and then when i turned it on, one of the circuits thats screwed to the big metal plate sparked into flames, i disconnected it (thinking it might work with one just connected) but then the other one just blewi sourced original replacement circuits direct from Marshall, and when received i fitted them the amp turned on and worked fine for about a week, with the exception of one of the speaker cones making a funny noise, during band practice again it blew, i drew conclusion that the speaker being damaged caused the amp to blowi ordered a genuine replacement speaker, replaced it, i got replacement 20mm 2amp time lag fuses, but every time i turn it on the amp buzzes and then a split second later the fuse blowsi have electrical experience with working with electrics on modern cars but not so much circuit boards,i have inspected the wiring loom and there's no sign of damage, no damage either on the circuit boardI can't afford to send it to marshall either for repairdoes anyone have any insight to my problemor know anyone than could fix iti can provide photos on request if it helpsany help will be greatly appreciated Quote Link to comment Share on other sites More sharing options...
Cabbage Posted November 23, 2007 Report Share Posted November 23, 2007 removing one of the speakers probably overloaded the power amp section, which caused it to blow a fuse then catch fire. as the AVT275 is a stereo combo, i'm guessing its got two power amps, one for each speaker, so when you unplugged a speaker its power amp has no load at all and died because of that. i may be wrong like, just a guess! what were you running into the speaker after you disconnected it from the AVT? you may have overloaded it with too much power from the other amp and damaged the speaker coil. running with one unloaded power amp could maybe have affected the preamp section of the amp, maybe caused a power surge, and damaged the valve or transistors? might be worth trying a new valve, see the original one is damaged. does the valvestate stuff have any digital bits in it? could have fried some thing in there? sorry i'v probably asked more questions than answered! have you given it the obligatory kick? i can usually sort out my noisy laney after giving it a big slap on the side! Quote Link to comment Share on other sites More sharing options...
sonhenry Posted November 23, 2007 Report Share Posted November 23, 2007 check the power supply. Quote Link to comment Share on other sites More sharing options...
Strat Harry Posted November 23, 2007 Report Share Posted November 23, 2007 Having some problems with my second hand Marshall avt275 mk 1first during band practice it died completely as a result of unplugging one of the speakers to used it for something else (bad idea, i know), i replaced the fuse and then when i turned it on, one of the circuits thats screwed to the big metal plate sparked into flames, i disconnected it (thinking it might work with one just connected) but then the other one just blewi sourced original replacement circuits direct from Marshall, and when received i fitted them the amp turned on and worked fine for about a week, with the exception of one of the speaker cones making a funny noise, during band practice again it blew, i drew conclusion that the speaker being damaged caused the amp to blowi ordered a genuine replacement speaker, replaced it, i got replacement 20mm 2amp time lag fuses, but every time i turn it on the amp buzzes and then a split second later the fuse blowsi have electrical experience with working with electrics on modern cars but not so much circuit boards,i have inspected the wiring loom and there's no sign of damage, no damage either on the circuit boardI can't afford to send it to marshall either for repairdoes anyone have any insight to my problemor know anyone than could fix iti can provide photos on request if it helpsany help will be greatly appreciated1. I sent a DSL-401 to Marshall, it cost me nothing for repair, but then the amp was just out of its warrantee and they were obviously feeling quite reasonable.2. What ever you have done, you have damaged the amp, no Nobel prizes for science there. If you get some half assed dufus like me to fix it on the cheap, you will spend your next gigs remembering how fuck witted the bloke who fixed your amp looked (and sounded) and have very little confidence that your next gig will not be without the alarming smell of burning silicon.3. Take my advice, at least give marshall a bell, they may surpise you.Good luck Quote Link to comment Share on other sites More sharing options...
fatboy Posted November 24, 2007 Author Report Share Posted November 24, 2007 from a site "the same, unrivalled design expertise that went into the pre-amp was also channeled into the design of the AVT power stage. Using frequency dependent power amp damping and their proprietary, dynamic clip level technology (which emulates the HT supply of a valve power amp), each AVT power stage creates the warm, musical feel and 3-dimensional sounds that made Marshall's all-valve power amps world-renowned. Also, all AVT products will deliver the goods in the often hostile and unpredictable environment of the live performance stage - which is why the AVT power amps of 50 watts and up are fan cooled for optimum reliability"i had the right speaker disconnected and was using it for vocals by having it plugged into the output of a mixed, this was being used at the same time as me only going through one speaker at about 2 o'clock on the master volume on OD2it's obvious the speaker got damaged by being driven too hard by the vocals and have got a replacement, but the amp blew when the vocals and guitar was going through it, it was the two sensor circuits for the fancy fan cooling system, the amp doesn't work with out the fans plugged in, these sensor circuits were bolted to a large metal plate and where they are bolted they are coated in heat sync, i replaced these and got the amp working fine, played it for about 2-3 hours bout 1 o'clock on the master volume and no worries, 4 days later played it again or 20 minutes and the fuse blew, the circuits i replaced were fine, i thought the dodgy speaker might have caused the amp to blow so i ordered a new replacement speaker, fitted it now as soon as it is turned on the fuse blows Quote Link to comment Share on other sites More sharing options...
Cabbage Posted November 24, 2007 Report Share Posted November 24, 2007 "Using frequency dependent power amp damping and their proprietary, dynamic clip level technology (which emulates the HT supply of a valve power amp), each AVT power stage creates the warm, musical feel and 3-dimensional sounds that made Marshall's all-valve power amps world-renowned. Also, all AVT products will deliver the goods in the often hostile and unpredictable environment of the live performance stage - which is why the AVT power amps of 50 watts and up are fan cooled for optimum reliability"just going on that tells you that there's a shed load of fancy electrickery gubbins in it! i'd gather some cash and have someone how knows how the thing works look at it, like strat harry said, you'd be pretty pissed when it breaks down on you after some half arsed repair! Quote Link to comment Share on other sites More sharing options...
fatboy Posted November 24, 2007 Author Report Share Posted November 24, 2007 do you know of anyone or anywhere that could look at the amp?i heard the place on nelson street, musical vision? may look at it but not sure Quote Link to comment Share on other sites More sharing options...
Guest Motleyal Posted April 4, 2008 Report Share Posted April 4, 2008 Don't use Bruce Millers. I've heard rumors that they get their tv repair guys to fix amps and they have fuck all idea.I've got a tsl 122 and it keeps blowing fuses. I fitted new valves and it worked well for about a year, then i got a high pitched squeal (polyphonic pick up or something or other). Tried a new set of valves and it blew again. I biased the valves per the book. Total fucking pain. I'm on the look out for a repair guy too. Quote Link to comment Share on other sites More sharing options...
fatboy Posted April 4, 2008 Author Report Share Posted April 4, 2008 yeah i made this thread last yearstill got the marshall sitting needing fixed cant afford to send it to them Quote Link to comment Share on other sites More sharing options...
steveosays Posted October 7, 2009 Report Share Posted October 7, 2009 I'm having a problem with my marshall avt 150 valvestateMy amp is not turning on and someone told me that it might be the fuse, I believe I need some assistance because I have no idea how to change or replace a fuse, but I don't really wana pay $70 dollars an hour for a repair. I hope someone knows or can give me advice on what to do? Quote Link to comment Share on other sites More sharing options...
britheguy Posted October 7, 2009 Report Share Posted October 7, 2009 My amp is not turning on and someone told me that it might be the fuse, I believe I need some assistance because I have no idea how to change or replace a fuse, but I don't really wana pay $70 dollars an hour for a repair. I hope someone knows or can give me advice on what to do?Better off on this site probablyThe Workbench - Marshall Amp Forum Quote Link to comment Share on other sites More sharing options...
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