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Yamaha G-5 guitar amp
Yamaha G-5 guitar amp
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Old 21st February 2010, 04:53 AM   #1
Yurk is offline Yurk  United States
diyAudio Member
Join Date: Mar 2009
Question Yamaha G-5 guitar amp

I have a friend who has this guitar amp. It's a 15 watt practice amp from the late 70s, I think. Some of the pots are shot.

I've been trying to find schematic or basically any other technical info on this amp on the web for a few hours, and I've gotten nowhere. I'm trying to find info on the volume/master volume pots at least. (Whether they're linear/log/etc.).

I'll have access to the amp in a few days and I can measure things for myself, but if anyone has any info on this little guy I'd sure appreciate it!


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Old 23rd February 2010, 03:24 PM   #2
scooperman is offline scooperman  United States
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Join Date: May 2005
Location: south Florida
Great little amp, nice nasty sound when dimed, decent reverb, and the wood case is attractive.

The 15W is AC power consumption. The G-5 is nominally a 5W amp, it puts out 7W@10%THD into 4 ohms. Start an Ebay search for the service manual, they come up every now and then, its only a few pages but its worthwhile having.

Bass,treble,volume, and master volume pots are shown as A25Kohm. The reverb pot is a B50K.

I have modded a couple of these for guitarists friends (and one for myself). I add battery backup so they can play portable or AC. Also, I have tried some circuit changes to get some more bass out of it. The stock coupling cap is 1000uF, if you go bigger you find that Yamaha got just about everything out of the stock speaker, you have to go to an extension cab with a better speaker for more.

Got a G-5 hooked to my laptop right now playing blues from koqx.
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Old 4th March 2010, 02:10 AM   #3
Yurk is offline Yurk  United States
diyAudio Member
Join Date: Mar 2009
Default Thanks!!

That's exactly what I needed. He still hasn't brought it by, but now I can get the pots ordered for when he does.

Thanks again.
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Old 11th May 2011, 04:54 PM   #4
pathdoc2 is offline pathdoc2  United States
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Join Date: Apr 2010
Just purchased one of these locally for $10! Sounds great and I love the wood case.
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