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March 25, 2023, 04:16:53 PM

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Yamaha G100

Started by semjmiyta, January 04, 2022, 06:38:33 PM

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I have a general consensus type question (kinda). I am playing through a Yamaha G100 just the head no combo all my Uber high high gain I get from pedals, Lately when it's time to jam it isn't the same .It's not tube so no warming up silicone trannies. So I'm thinking my same settings day to day won't change for a few weeks but some of the screaming sustain I'd get would be there one or 2 days not there the next day etc. No change of strings pots nothing . So.
Seems the obvious choice
Seeing I love high gain all through pedals it'd be a win win No?
Cleaner amp. Thoughts and suggestions anybody?
I have the series one G100 series 1 running through an old Altec Lansing 15" and when the Yamaha is kicking it screams I love it  but when it's not can't seem to dial in anything close just figured I'd throw it out there before I go for it


My first reaction would always be check the FX loop jacks.  But I don't think you have them, do you?

I love these amps.  The power amp is on the heat sink assembly hanging from the chassis.  A couple large bolts and it unplugs from the interior board by a 6-pin connector.   Just my guts hunch, but pull that assembly off and check the pins on the connector.  Any cracks on the pin solder?  or just simply resolder them anyway.  Likewise, inside, I think it is the power supply board has the mates for the six pins, resolder those.

It could be anything, of course, but caps don't come and go.  You have a symptom that does come and go.  I'd be looking for a failing connection.  A weak solder joint or a jack with poor contacts.

You have two channels, do BOTH channels act the SAME way?

And just a thought, you have hi and low jacks for each channel.  You likely use just the HI.  Plug into the LOW jack on a channel.  Does that sound like the "problem" condition?  If the cutout contacts in the LOW jack are dirty, the amp will stay in the low condition even using the HI jack.


Thank you very much for the info. And correct no fix loop and a high low input and a preset volume which I'm guessing is the channel switch I'm familiar with the boards you're mentioning as I've had to repair a really word diode attached to the big heat sink and you were right again about the jacks (the speaker out jacks are these huge screw type old switchcraft type that I did have to clean
Would any transistors maybe too old now cause it to be lack luster?
I'll check those pins you mentioned for sure thanks again


This doesn't sound like a transistor issue.   They don't age like tubes.  My favorite example of transistor life:  NASA's Voyager satellites.  They run on transistors, and have been running now for 40 plus years in the cold of outer space.   They are way past the edges of the solar system, the temperature is a few degrees above absolute zero, and the little thing keeps sending back messages...it is working.


Thank you again for your response . I didn't 100% think it'd be the transistors just kinda tossing jello at the to see what sticks I could be way off thinking it's the amp. Next will be what probably should have been the first to check , my patch cords and cables
If nothing there my electronics in my guitar then anything else so I  could narrow it down a bit and if it is my amp then I'll post (hopefully)with a bit more detail.
Take care and thanks again