Trace Elliot GP7 SM 300W Combo > Low volume then distortion after 1 / 2 mins > Advice gratefully received!

[Bassfingers]

Hello.

 

I'm hoping the formidable BC "Hive mind" will be able to help here. 

 

I have an old Trace Elliot GP7 SM 300W Combo amp which has always had home use only. It is now surplus to requirements and I was planning to sell it on. It is still in good cosmetic nick. 

 

However, I tested it out today and the volume seemed  lower / weaker than usual. Then after a minute or two, the signal becomes distorted. 

 

I've been through the usual checklist: 

 

Reduced input level

taken the EQ down a few notches

tried with both active and passive basses (no difference)

Reduced Master output level 

 

The distortion continues regardless. 

 

I'm not experienced enough to tinker with the internal gubbins. 

 

I'm wondering whether to 

A) sell it as is, for spares or repairs

B) Get it fixed (if it sounds like a fairly straightforward / inexpensive fix

 

Does this sound like the speaker has blown? Loose connection somewhere? I just wondered if this sounds like a common fault. 

 

Any advice / thoughts gratefully received 🙃

 

[PaulWarning]

I had something similar, was the output transistors,  cost me about £130, you could try bypassing the preamp by plugging into the effects return while using a FX pedal to boost the volume, if it still sounds distorted it means it's the power amp or speaker, try a different speaker if you've got one to see if that's the problem

[Bassfingers]

Thanks Paul, sadly I don't think a £130 outlay would be worth it in this case. I will give the effects option a whirl though. 

 

 

[Downunderwonder]

The other easy check is to insert a cable between fx out and return. This bypasses the fx loop interruption that connects preamp to amp when loop is not being used. Sometimes the contact gets corrosion on it and fails to transmit the signal onward.

[Bassfingers]

Thanks @Downunderwonder- I'll give it a go 👍

[rmorris]

On 05/01/2022 at 15:18, Bassfingers said:

Thanks Paul, sadly I don't think a £130 outlay would be worth it in this case. I will give the effects option a whirl though. 

 

 

 

I'm guessing that the £130 was for a tech' repair bod to diagnose / source transistors / replace / test.

If you're happy to source transistors yourself and fit them - or get someone you know to do it - then it should only cost a few pounds (and maybe a couple of drinks) so might be worth a go if the effects option isn't successful.

[Bassfingers]

13 hours ago, rmorris said:

 

I'm guessing that the £130 was for a tech' repair bod to diagnose / source transistors / replace / test.

If you're happy to source transistors yourself and fit them - or get someone you know to do it - then it should only cost a few pounds (and maybe a couple of drinks) so might be worth a go if the effects option isn't successful.

Thanks for the advice. Good point.  

[rmorris]

Link to schematic / service info. Note that there are two versions of the power amp (Bipolar and MOSFET).

 

https://www.freestompboxes.org/download/file.php?id=7186&sid=c6fb8545ee36a61fbad7c8ad3ddcc8da

GP7 150.300watt SM series Trace Elliot.pdf

Edited January 7, 2022 by rmorris
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[Thunderbird]

Wonder if a speaker wire has come loose in transit do those amps use the little push on spade type connectors? 

[Thunderbird]

Wonder if a speaker wire has come loose in transit do those amps use the little push on spade type connectors? 

[Bassfingers]

7 hours ago, Thunderbird said:

Wonder if a speaker wire has come loose in transit do those amps use the little push on spade type connectors? 

Possible - Looks like I will need to open it up and have a poke around 🤞