HELP repair a Yamaha T100C combo

packman · 9th May 2009, 04:07 AM

Hi friends, need experts aid today.
I've bought an used Yamaha T100C combo, a Soldano project
realized by Yamaha in the '90.
Great amp but... clean channell is broken! Overdrive channell works OK but when i switch to clean channell i hear a low volume distorted sound, with input level and master at the max i can hear only notes played strongly like a heavy noise gate that block all the sounds under a certain level.
Changing the valves seems not resolving.
Where i can start my tests?

This is the scheme of the amp:

http://www.blueguitar.org/new/schem/...o/yam_t100.zip

Any advise will be higly appreciate, thanks in advance.

mjf · 9th May 2009, 08:58 AM

hello.
i would check the parts around v1 (input tube).
power off!dangerous!
try to measure the resistors,look for a bad soldering point,bad caps.clean the switches,pots......with a contact spray.
greetings.........

packman · 9th May 2009, 09:05 AM

Thanks, i'll try that.
Meanwhile after the first post i've put the guitar on the EFFECTS RETURN jack to bypass first stages and the problem remain.

9th May 2009, 04:07 AM	#1
packman diyAudio Member Join Date: Sep 2005	HELP repair a Yamaha T100C combo Hi friends, need experts aid today. I've bought an used Yamaha T100C combo, a Soldano project realized by Yamaha in the '90. Great amp but... clean channell is broken! Overdrive channell works OK but when i switch to clean channell i hear a low volume distorted sound, with input level and master at the max i can hear only notes played strongly like a heavy noise gate that block all the sounds under a certain level. Changing the valves seems not resolving. Where i can start my tests? This is the scheme of the amp: http://www.blueguitar.org/new/schem/...o/yam_t100.zip Any advise will be higly appreciate, thanks in advance.

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9th May 2009, 08:58 AM	#2
mjf diyAudio Member Join Date: Jan 2009 Location: upper austria/near linz	hello. i would check the parts around v1 (input tube). power off!dangerous! try to measure the resistors,look for a bad soldering point,bad caps.clean the switches,pots......with a contact spray. greetings.........

9th May 2009, 09:05 AM	#3
packman diyAudio Member Join Date: Sep 2005	Thanks, i'll try that. Meanwhile after the first post i've put the guitar on the EFFECTS RETURN jack to bypass first stages and the problem remain.