Yamaha G50-112 Schematic Needed

[telecaster]

Anybody have a schematic for this Yamaha single 12 guitar amp combo? The model is G50-112. Appreciate any help - thanks.

[Enzo]

Maybe, I'd have to blow the dust off some old files.
What's wrong, I usually didn't have to get out the drawings for Yamahas. Blown outputs were usually just the power tranasistor.

[vintagekiki]

Chuck
Yamaha amplifiers series G50 … 100 is produced as single (effect) or dual (clean and effect) channel amp in two basic version SS and IC.

SS or Yamaha series G50 … 100/ I is vintage version with transistor preamp.
http://www.ampix.org/albums/userpics...0_series_I.pdf

IC version produced in two version Yamaha series G50 … 100/ II and Yamaha series G50 … 100/ III. Difference between II and III version is in power amp section.

I have somewhere schematics for Yamaha series G50 … 100/ II. For several days I scan to you

[telecaster]

Amp came to me for repair with a note that simply said "blowing fuses". It has a Primary and Secondary fuse, both 2A, and both have been neatly wrapped with tinfoil. I am thinking output transistors too, but I'd like a schematic because I suspect the tinfoil bypass may have caused additional damage. Upon opening the amp, I was pleased to find that Yamaha added a second fuse hardwired inside the amp (blown), in series with the Primary, which hopefully saved the transformer. The Secondary fuse goes to a separate power supply board - I'll trace this out and see if any components were damaged (schematic or board layout would be helpful here too).

[vintagekiki]

Chuck
Here is Yamaha series G50 … 100/ II for first aid.
PCB board layout coming soon for several days ...

[telecaster]

Thanks vintagekiki, those schematics were similar enough to help me understand the power supply. This amp has the transistor preamp (no IC's). The power supply board is LC15963, the preamp board is LC80123 and the power amp board is LC15972. I unplugged the power amp and was able to verify that the power supply seems to be ok. I'll check the output transistors out next.

[Enzo]

Are the output transistors on a largish heat sink mounted to the chassis by two large long bolts running all the way through it? Bolts maybe 4-5" long? Seems to me there was like a Molex connector and the heat sink assembly came unplugged from the chassis then. I could also be remembering somehting else.

But you have the original G50 then, not the later revisions.

For comparison I posted the G50-112 schematic and also a page of tech data and adjustments on www.ampix.org

[telecaster]

Enzo, you are correct - this amp has the assembled power board and heatsink in a separate assembly that removes from the chassis with two long bolts. Power and signals are connected with a 6-pin connector. I checked the schematic you posted on ampix and it matches this amp - thank you!

[Enzo]

Sorry for the small size, the paper copy was already a reduction.

[vintagekiki]

Chuck
Here is Yamaha series G50 … 100/ II schematics with pcb

http://www.ampix.org/albums/userpics..._series_II.pdf

[telecaster]

Thanks vintagekiki and Enzo for the schematics. It was a shorted component on the power amp board. Back working, it's a decent sounding amp.

[Kareem33]

Yamaha Guitar Amplifier?

I have one of these amps, but it appears to be a variation on the above schematics/links?

It has:

• Pre-Amp Board - LC 80123
• Power Supply Board - LC 15965
• Power Amp Board? (Can't immediately see one! Is it hidden from plain sight?)

The biggest difference from the above schematics is that it only has a distortion footswitch and record out, no reverb footwitch out or unit.

Other codes I can find on components are:

• J115B
• GA-0244
• O-SM20l

Can anyone please:

• Direct me to the correct schematic for this variation or at least inform me the model of this variation so I can ask for the right one from Yamaha?

Thankyou.

[vintagekiki]

model Yamaha G50..100/ I or series I (transistors preamp)
Pre-Amp Board - LC 80113 -Normal ch.
Pre-Amp Board - LC 80123 - Reverb ch
Power Supply Board - LC 15965
Power Amp Board - LC 82080

Code PT for 220V
GA-0245
2-SM19B

http://www.ampix.org/albums/userpics...0_series_I.pdf

[Kareem33]

Yamaha G100-410 Guitar combo Amp 410 4x10 speakers

Thanks for the assistance.

However I have FINALLY worked out my Amp is the above model, heavily modded by previous owner though so that the reverb is removed from the Pre-Amp Board, and the tremelo effects and pre-set volume PCB are gone altogether! Quite bizarre...

Any truth in the notion I read on line that these Amps were designed by Soldano?!?

Original:

[Enzo]

I think you have in mind the Yamaha tube amp, which was Soldano dedsigned. These old solid state amps, not likely his work.