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bbrich

Trace Elliot 715 Series 6 GP7 100w Combo

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I bought my Trace Elliot 715 100w Combo way back in March 1991 and I've been using it probably 7 or 8 times a year since then. I'm very careful with my gear and the combo still looks almost new even though its over twenty years old. Considering its a single 15 inch speaker the sound is absolutely fantastic. I've had unsolicited compliments from a number of bassists and musicians over the years and I've become accustomed to the sound quality of this amp. So much so that I just don't feel comfortable with any other similar combos - Fender, Peavey, etc. Its not about money, they just don't sound as good to me.

The amp started to develop a problem a few years back. By the time I would get towards the end of a gig the output volume would drop off dramatically. If I turned the amp off for a while it would recover - suggesting that something was overheating. I started to use a parallel back-up on stage (Marshall) in case the Trace failed. In the meantime I had an electronics man, and fellow musician, take a look at it. He said there was nothing wrong with the power amp side of things and he thought that the Input stage was failing - perhaps due to my "hard" playing style.

I think the Trace Elliot Input stage of that era had a gradual cut-off whereby if the signal from the bass was too high or if the gain was too high then the warning light would slowly start to flash after which the input stage would reduce the amount of signal coming in. My friend checked the input stage and said that he couldn't find anything wrong with it. I got all new jacks and pots from the States and he fitted those just to be on the safe side and we left it at that. It appeared to be working fine until yesterday. At sound check the Trace wasn't working at all. With the bass volume flat-out and the input gain up full you could just about hear a faint distorted sound from the speaker. I had to use the Marshall and run through the PA as well.

Has anybody out there encountered, or can remember encountering, a similar problem with this generation of the GP7 Pre Amp and does any body have a schematic of this model or any other ideas?

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Yes, thanks for those words of encouragement. I've just re-read my post and I've noticed that I left out a critical piece of information - I'm in Saudi Arabia. So the concept of buying a new amp back in the UK and flying it out here (these days) is a non-starter. The airline or the baggage handlers would probably demolish it. A full-flight case would be un-manageable. Buying online would incur prohibitive shipping costs and buying one here I'd be limited to a practice amp or at best an 80-watter. That's why I'm trying to find a repair solution. I'd consider buying a second-hand amp off e-bay next time I'm back in the UK and taking the amp head out of the cabinet. I could manage that. But if this is a common problem related to age (the amp not me) then I'd probably be no better off. Thanks for the response though - at least I know somebody's read my plee...

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Thanks for the info. I've got the local electronics genius looking at it right now. I hope its something relatively simple like your AH200 dry joint. British Audio Spares don't have any major parts in stock for that generation of GP7 & AH so I'm hoping it can be fixed at component level.

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[quote name='bbrich' timestamp='1370026144' post='2095786']
British Audio Spares don't have any major parts in stock for that generation of GP7 & AH so I'm hoping it can be fixed at component level.
[/quote]

That shouldn't be a problem.

Those old TE's were all 'off the shelf' parts as far as electronics were concerned - no strange bespoke IC's or obscure parts. :)

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My TE V-type was doing a similar thing. It's now fixed and as Aussie suggested, it was a few dry joints. Probably the same problem as my amp is a similar age to yours.

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[quote name='icastle' timestamp='1370036869' post='2095990']
That shouldn't be a problem.

Those old TE's were all 'off the shelf' parts as far as electronics were concerned - no strange bespoke IC's or obscure parts. :)
[/quote]Thanks for the info. Its looking like the output transistors though. New ones going in as we speak.

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Take note all of you out there with ageing TE's. Update. It turns out that a transistor that controls the current flow from the power supply to the Pre-Amp is starting to boil its bum after an hour or so of playing. The hotter it gets, the less current it allows through resulting in reduced volume and reduced tone control and eventually cutting out altogether. Could this be my (and your) problem solved? Watch this space.

Edited by bbrich

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Jan 2014 update. I finally got my combo sorted out. My electronics friend ripped it to pieces and discovered that the power stage was on the blink as well as the transistor between the pre-amp and power stage. Due to the nature of playing outdoor gigs in a desert climate (40-odd degrees not uncommon in the summer - which is when it finally died) he also thought that a cooling fan would be helpful. So he replaced the transistor and asked me if I wanted to have a new power stage and fan fitted. After he assured me that the Trace Elliot sound comes from the pre-amp not the power amp and that the sound should be the same after the modifications, I agreed and, for about 200 quid, he fitted a new fan-cooled 300W power stage. However, this meant that a new speaker would also be required.

The original amp was putting a very conservatively rated 100W into a dedicated 4ohm speaker. With the new 300W rating we decided that a Celestion BN15-400S 4 Ohm Neo Bass Speaker might fit the bill. Obviously you can't really audition a speaker - you just have to take the gamble. So, for another 180 quid and about 40 quid to ship it to Saudi Arabia, we fitted the new speaker. And…

It all works perfectly. It sounds fantastic - just like the original but instead of setting the volume at 4 I thought I'd better drop it "a click" to 3.5. Drummer told me it was too loud (!!) Drummer!!! So I'm now only allowed 3 on the loud knob. We played two nights running in December and the amp sounded great and the heat sink remained stone cold. Looks like I've got a result that's probably saved me about a grand and a real load of shipping hassles.

So, if you've got an old TE that's fading out on you, get your local electronics guru to measure the temperature of that transistor between the pre and power amps under constant heavy load. If its getting hot, replace it. It could just save you a fortune.

I hope this long-winded blurb helps somebody somewhere.

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Excellent thread and result. Stuff like this is priceless in the Repairs section, nice one. That amp should now probably go on longer than you do :)

Cheers

Geoff

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Good to see a class piece of kit being given a new lease of life! I had 3 GP7 combos on the trot over a 20 year period.....only change to Markbass when my back got fragile. Still miss em.

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Thanks for this. I've saved the thread for future reference in case my GP7 (which I've also owned since 1991) ever plays up.

Apart from some occasionally crackly pots, it's fine. Not bad for 23 years, really.

Edited by desmondpot

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[quote name='bbrich' timestamp='1372697112' post='2128748']
Take note all of you out there with ageing TE's. Update. It turns out that a transistor that controls the current flow from the power supply to the Pre-Amp is starting to boil its bum after an hour or so of playing. The hotter it gets, the less current it allows through resulting in reduced volume and reduced tone control and eventually cutting out altogether. Could this be my (and your) problem solved? Watch this space.
[/quote]

Amazing, now 22 years old, I installed a new 300w MOSFET power stage and power supply into my (once 80w) series 6 GP7. Following that, I had this exact problem, didn't replace the transistor but attached 2 flanking bits of copper to act as heat sinks and viola, beautiful, rich, deep sounds returning, sounded stonking at a rehearsal last night and kicked it for a solid 3 hours!

Many thanks for this worthwhile tip!

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Update. Two years since we made the modifications and my amp continues to perform flawlessly, more than can be said for me.

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And a further update. Its now just over five years since we modded the old TE715 and its still going strong, sounding fantastic. No other components have died and the replacement 'new old stock' jacks and pots haven't got to the scratchy stage yet. However, I've deteriorated significantly during the same period and now have to employ younger, fitter people to lift my kit on and off the stage!!!

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Hi bbrich.

I've suddenly developed a similar problem with my Trace Elliot 715 combo. Large decrease in volume and loss of tone. Can't find the fault. You referred to a transistor between the preamp and power stage. Do you know designation of the transistor or maybe a pic. There is a small rectangular board between the preamp board and power stage. It has a component which looks like a small three leg transistor (the only one of its kind on the board) but the schematics for the 715 identify it as a Triac. Would this be what you are referring to? Any help appreciated.

Cheers Gav (Nivagues)

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