Yamaha G50-112 owners manual wanted

[rami939]

UpstairsDave,
did you install the potentiometers that you purchased for the Yamaha G50.
If so,did they made any improvement on the amp.?

[upstairsdave]

Absolutely. It's like putting new spark plugs in an engine. Cheap guitars have cheap POTS and sound cheap but more so, they don't have the ability to change the volume or tone over a wide range of motion of the POT. I've tried some Epiphone Les Paul Customs made in China versus one made in Indonesia and the Chinese POTS are junk. Go to your local music store and try an Epiphone compared to a higher end guitar and notice how the tone varies from the cheap guitar to the better one. That said, if your POTS are old and worn out, they can't function like it did when new. The trouble is that you don't notice the deterioration in performance casue it happens over a long period of time. I had a friend with a 70's Les Paul that kept breaking up on him. He's pull on the guitar cord and mess with the input jack on the amp. It was to the point of letting him down in the middle of a gig. I went up and listened to the amp with and turned the volume POT. It crackled and had an open spot, particularly at one spot, the spot he always played at. So I changed out all four POTS, the input jack, and the PUP switch. He complained that the volume POT didn't turn as easily as the old one. Well, no wonder, it was shot. See, he forgot what the volume POT was like when new. So, replace them all if you can find them. Check out Mouser Electronics. I got all my stuff from them. Mine had three different knobs on it when I got it. I put all new knobs on it, They aren't like the originals but the ones I g ot have a set screw. Not the cheap push on knobs. I didn't find two of the POTS that are in the amp. I forget which control they were for but the one had a sire coming off the top of the POT and a black wire soldered to the board and the other one had a double resistor driven off the main shaft. They weren't a problem and are noise free. I'm still looking for them but they work, so why fix em as the saying goes. I made a post about the input jacks. They are mounted onto a board. If mine goes bad, I'll put two new jacks in the amp and hard wire them to the board. Like in the old days of point to point wiring. If I find a cheap G50-112 II, I'll buy it for parts but being that old, the parts may be just as bad. An extra board would be nice to have but that's way over my skills in diagnosing.
Hope this long winded ditty helps. Read the reviews on Harmony Central on the amp. It's exactly what they talk about in this amp. I'm glad I took a shot on it at a local auction. I bought it without hearing it. I actually didn't pick it up either. I thought it was going to be light because of being solid state. I carry it around in both arms instead of one hand and use a hand truck. I've got a bad back.
Later
Dave

[rami939]

Upstairs Dave,
I would like to change the pull up switches (3)the volume and reverb as well.
You posted a list of items that you bought from Mouser elect..
Are those potentiometers in the list ?
I went to the mouser web site and look for the parts numbers,but I don't see any pull out switch.Maybe is me,don't know.
Could you clarify a bit on this.
Are they easy to change ?
Thanks.

PS:do you have any picture of your amp after the changes to share?

[upstairsdave]

Here's the link to the push pull POTS. I forget what the value i9s on the reverb POT. Pull your chassis out and look in the case of the value.
RV16BF-20-15R1-B54 Alpha (Taiwan) Panel Mount Potentiometers
For the other parts, just go to the Mouser site and type in the part numbers I listed above. You'll need a solder iron that has a suction device attached to the solder gun to remover the solder from the board. Buy another low wattage soldering pencil to install the ROSIN Solder only. Do not use acid solder. I didn't take pictures after I was done. It won't look any different.
Good luck
Dave

[upstairsdave]

Another thing about the POTs. I bought new knobs to fit the shafts. These are solid shart and not serrated shaft POTS. The old push on knobs won't work. Dress it up and but $10 in new knobs.

[rsteven46]

Need help to fix high and low input jacks in a yamaha g50-112. Can anyone send a picture of theirs from the inside with it showing the wires and where there are connected or maybe send a schematic that is easy to read. I got a hold of a schematic and my friend and I tried soldering the wires according to the schematic so I don't know if we solder it wrong cause now the high input Jack isn't working and now the low input Jack is working so it completely changed.

[J M Fahey]

Hi rsteven.
You should have bought the exact same jacks they used, because a generic one, as is, has different pinout.
I see they are soldered to a small PCB, which is then connected to the main preamp board with 4 wires.
If yours are different, post a couple of clean, sharp pictures and I'll tell you how to wire them, without the miniboard.

[Jazz P Bass]

Here is the schematic of the jacks.
Wire it exactly as you see it.

[J M Fahey]

Hi jazzp
Can you please post your full schematic or manual, either here or at Ampix if too large?
The one I was referring to was , now that I look again, G50-112 Series II which I see is very different.
I found it at Ampix, kindly posted by Enzo.
Thanks.

[rsteven46]

I got the schematic at schematics.ca or something. I have a model 1 yamaha G50-112 so yeah. I took a look at it again and one of the wires came off on the high input so I am think that was the problem and why it wasn't working. If it works i will tell you guys but if it doesn't then I will post pics for you. Btw my reverb is not working any ideas? I am guess it is the pot because there is no resistance when you turn the reverb pot so is that why the reverb isn't working? Well I actually prefer reverb pedal but any help is fine

[Jazz P Bass]

G50-112 schematic.

[rsteven46]

Pics of the wiring of the input jacks

This one works

This one doesnt.

all the wires are solder correctly did I read the schematic wrong and what is the tape wire for its connects both but not sure if i connected it in the right place.

[zeezak]

Here's the scan. It's not real high-res to save some space, so if you can't read something let me know.

I realize this has been many of years...but you're PDF file just becomes a blank page. Am I doing something wrong?

I'd like to know more about this amp. I have gotten it from my drummer. The speaker was gone and I made this into a head. I would like to know about the dual imputs with the a/b switch and the dual power switch, how it can be turned on up and down.

Thank you

Zak

[JoeM]

I'll see if I can locate my original scan.

[Enzo]

You did nothing wrong, a server crash lost our stored files.

Dual power switch? DO you mean the main power switch which is off in the center and on to either end? You can flip the switch either way. Usually it doesn't matter, but sometimes, one position will hum a little less than the other way. That is its purpose. (What it is doing is reversing the mains wires to the power transformer.)

The two input jacks should be labeled high and low. The high jack will be a little louder than the low, by 6 decibels. This is just like a zillion old Fender amps. Mostly use the high jack, but try the other, sometimes things are happier there.

A/B switch? I don't have the amp here, but I am assuming that is the overdrive selector.