Phil_bassman Posted February 15, 2021 Share Posted February 15, 2021 Hello everyone I hoping I can get some advice on this as I cant seem to find anything on the internet about my intermittent problem with my Trace Elliot head I have a Trace Elliot GP12 SMX 300, awesome amp but has been the bairn of my life for problems!. It has blown twice (transistors went!) and its been fixed and serviced to get it running again by a trusted amp electronics technician. The problem that I'm having now is the amp keeps cutting out while I'm in mid practise with the band. I play with an active bass so I do not push the amp very much (doesn't go past 4 on the volume) The only way to describe this is that is just stops my bass from making sound and then it producing a very harsh earth buzz that comes from the speakers (the sound is similar to that off your thumb being put over a guitar jack while its plugged into a distorted guitar amp) This sound is horrific. But when I turned the amp off at the back and switch back on (in a matter of seconds) its fine again. I'm completely baffled at this and so is the guy that has fixed my amp. The only thing I found similar to this problem is on this site from a guy having similar issues with his GP12 SMX 250 combo where his cut out out at a gig but made a screeching noise instead of horrible hum like I get through mine. That guys problem people said its the amps valve but I'm very uncertain on this. One thing I will mention, is that it seems that the amp only does this when im practicing and when its cranked up abit, as when im at home practising at suitable levels (i played for two hours straight once to test this) it didnt do it! Any help will be most appreciated! Kind Regards Phil Quote Link to comment Share on other sites More sharing options...
DrDrill Posted February 16, 2021 Share Posted February 16, 2021 I had a similar issue many moons ago, sent it away several times, came back the same, then I found a post somewhere about the jack sockets on the effects loop tarnishing/corrosion. Fix was to poke a lead in and out the ALL of the jack sockets on the amp (when it's switched off) several times, solved the problem for me. It might be that something more technical is causing your issue but this doesn't cost anything to try. 1 Quote Link to comment Share on other sites More sharing options...
Hellzero Posted February 16, 2021 Share Posted February 16, 2021 As @DrDrill said it really sounds like an effect loop problem. Just put a (small length) patch cable from the send to the return : if the problem disappears you can leave it so and put some contact cleaner or have the two switching connector jacks replaced. It's a very common problem, especially if you never use the effect loop, but too often forgotten by techs. And NEVER cut and start immediately anything with power capacitors or you'll blow them. Just wait 10 to 30 real seconds to empty them totally and start again. Quote Link to comment Share on other sites More sharing options...
wright/watt Posted May 12, 2021 Share Posted May 12, 2021 On 16/02/2021 at 10:11, DrDrill said: I had a similar issue many moons ago, sent it away several times, came back the same, then I found a post somewhere about the jack sockets on the effects loop tarnishing/corrosion. Fix was to poke a lead in and out the ALL of the jack sockets on the amp (when it's switched off) several times, solved the problem for me. It might be that something more technical is causing your issue but this doesn't cost anything to try. This worked for me the other day so thankyou 👍😃 Quote Link to comment Share on other sites More sharing options...
DrDrill Posted May 14, 2021 Share Posted May 14, 2021 On 12/05/2021 at 11:36, wright/watt said: This worked for me the other day so thankyou 👍😃 No sweat....the bill's in the post 1 2 Quote Link to comment Share on other sites More sharing options...
Bleat Posted May 16, 2021 Share Posted May 16, 2021 (edited) I had a Trace 250 SMX head years ago that did this. It went off for "repair" several times but the problem just came back every time. I used to find that the gentle art of thumping the top of the amp several times used to work... sometimes. Got rid of the damn thing in the end... Trace Elliot , never again ! Edited May 16, 2021 by Bleat Quote Link to comment Share on other sites More sharing options...
Dan Dare Posted May 19, 2021 Share Posted May 19, 2021 Sounds like a dodgy solder joint. When you switch off and on or bang on the top, the vibration remakes the connection temporarily. Only sure way to fix it is for a repair person to check every joint. Fiddly, time-consuming and likely expensive as a result. Quote Link to comment Share on other sites More sharing options...
b7l4s Posted June 16, 2021 Share Posted June 16, 2021 Late to the party I know, but I've also experienced the effect loop tarnishing issue on both TE and Laney amps, presumably because they are unused for years by some owners (including me). But posting because I'm sure I've also read that the pre-shape and graphic in/out switches on some models of TE amp could be problematic, and that replacing them had been known to resolve some intermittent issues... Could be useful info for someone. Quote Link to comment Share on other sites More sharing options...
TheGreek Posted June 16, 2021 Share Posted June 16, 2021 Sounds like your TE needs a service. I have mine done by Mal Crawford in Stevenage - always improved by his work. IIRC I've left his details in the Amp Tech thread. 1 Quote Link to comment Share on other sites More sharing options...
rmorris Posted June 20, 2021 Share Posted June 20, 2021 On 16/05/2021 at 15:05, Bleat said: I had a Trace 250 SMX head years ago that did this. It went off for "repair" several times but the problem just came back every time. I used to find that the gentle art of thumping the top of the amp several times used to work... sometimes. Got rid of the damn thing in the end... Trace Elliot , never again ! I had / have (haven't powered the amp for a while) a similar issue with a Trace GP7 (early model). Mostly fine and dandy but will sometimes drop in output level dramatically and sound goes all wrong. 'Thumping' it sometimes resolves it - for a short while anyway - or power on/off. If it's not going to work straight after powering I can tell as it makes a different and louder turn on thump noise compared to when it's all good. Previously it went off to some ex-Trace people in Essex to look at this. Lots of resoldering in the power amp section but the problem still apparent intermittently. Resevoir Capacitors changed esp since >20 years old but no change. And I've been over solder joints and renewed the thermal grease for the output transistors...still has a problem. Quote Link to comment Share on other sites More sharing options...
DGBass Posted June 22, 2021 Share Posted June 22, 2021 While I've not had any experience with the SMX heads, I do have a series 6 GP12-200 head. Other than replacing serviceable items like the coupling caps on the mosfet power board and the bridge rectifier diodes( my amp was made in 1992 and the originals were only changed last year due to a developing hum), I've found these amps super solid and reliable. The SMX is a bit more complex in that it has a back board like the Ashdown ABM's and a Multi pin connector from the pre-amp board to the back board. If the amp cuts out after a thrashing or responds to a thump on the case when it cuts out, it could possibly be either heat related (perhaps a dry joint on the power board somewhere) or perhaps the multi pin connector between power board and pre-amp is not fully home in the socket or shaking loose. For heat issues and if your SMX has the big cooling fins at the back, these power sections MUST have proper thermal compound applied in copious amounts or they can easily overheat and cut out / blow expensive Hitachi mosfets. For pre-amp issues, I had an ABM which had very similar symptoms to what you describe and the fault was traced to the multi pin connector/ribbon cable from pre-amp to back board. It was vibrating loose and generating all sorts of strange loud earth type hums and buzzes. And cutting out. On ABM's, the pre-amp signal routes off the pre-amp board via the multi pin connector cable to the back board and back again in a loop. So any issues with the ribbon connectors can cause all sorts of weird and difficult to trace issues. A bit of hot glue applied to the the multi pin connectors to stop them vibrating loose at both ends solved the problem for me. Clive Button did a lot of design for Trace and Ashdown at the time so there are a lot of similarities between ABM's and TE SMX amp designs with the valve pre-amp. Quote Link to comment Share on other sites More sharing options...
b7l4s Posted June 23, 2021 Share Posted June 23, 2021 Good shout to look carefully at the multi pin connectors if your amp has them - they are not the best solution to connecting boards in an environment which will likely experience a lot of vibration... Quote Link to comment Share on other sites More sharing options...
rmorris Posted June 23, 2021 Share Posted June 23, 2021 (edited) 8 hours ago, b7l4s said: Good shout to look carefully at the multi pin connectors if your amp has them - they are not the best solution to connecting boards in an environment which will likely experience a lot of vibration... If they are like the black multipin pre to power connector in my old GP7 head then it probably is a good solution to interconnection. I think the manufacturer is AMP. The connectors are basically aimed at automotive / vehicular applications and there are definitely vibration issues in that environment. They can seem not very 'solid' as the pins noticeably move (ie 'floating' pins) but is a deliberate design point so that the connection can move within limits and not snap as they might if 'solid'. They have a good deal of contact area so should be fine esp as they would be disconnected only for service or maintenance. Problems can and do arise where the quality of the crimp connection is not good - inappropriate size / type of wire or crimping technique / tooling in poor condition... Edited June 23, 2021 by rmorris Quote Link to comment Share on other sites More sharing options...
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