Identifying different PT primaries

[EETStudent]

I've got an amp that can switch between primary voltages. However, the cheaply made female mains socket broke on me, and I'm ready to go ahead and just attach the power cord to the 115V primary. But since there are about 9 different wires going into the primary side, I cannot locate the ones I need. I have posted a schematic, but I don't know how accurate it is seeing as there are several other circuit variations.

Anyway, I have identified a single white wire, assuming that is neutral. I then notice a black and black/white, blue and blue/white wires. Is there a standard color scheme for different voltage wires?

[Enzo]

If you told us what the amp was, perhaps we could just look up the wire colors.

[Chuck H]

Of course he has a model number and tried to LOOK UP THE WIRE CODES. Otherwise he wouldn't be asking. If it was as easy as using the model number to LOOK UP THE WIRE CODES then why would he need to come here? He would just LOOK UP THE WIRE CODES for himself.

Chuck

[Enzo]

So I'd be CRAZY to suggest the SCHEMATIC then?

[EETStudent]

Its a pretty new amp. Gibson GA42. Heres the schematic, dont know that it'll help...

I did try some color code research, but I couldnt conclude much of anything. I'll look a little more though

[Amp Kat]

That is about the worst schematic of a dual primary drawing as I've ever seen. Your going to need a better drawing to figure out which colors are which. Two of those wires will be wired together to complete the Dual Primary and then two more will be used for the 115 volt fused mains hot and common. I'm sure there is a way to ohm them out but 12 wires is going to be a pain but could be done. Theres got to be a more precise drawing from Gibson somewhere. Is this a Weber kit ?

[EETStudent]

Nope, the schematic and the amp are straight from Gibson. I figured the schematic would be useless.

Couple things, I'm noticing the 100, 115, and 230V primaries. You mention it being a dual primary, wouldnt it be a triple?

Also, I'm willing to try to ohm it out. What kind of measurements am I looking for?

[6267]

I'd use a reference voltage and assume that it's the black wires. Watch the flying leads though, use one hand.

[Amp Kat]

A small reference voltage from a variac would be the way to go with the two black wires but the problem is you need to know which two wires to bridge together to complete the dual primary or that's not given you anything close to the right secondary voltage. What colors are all of the wires ? The Japan 100 are usually plain white so if you see that you can eliminate those. The two black are most likely the two windings from top to bottom of the whole winding after the dual primaries are connected. I guess you could call it a triple primary but you only want to connect two.

[Enzo]

It is a dual primary because there are two windings, the number if voltages it can serve is not what makes it dual or triple.

The switch drawing tells the tale once you fogure out what they are representing. There are the six horizontal buses, then the thin vertocal lines indicate which are shorted together in each position. No help on the colors though.

But since this is a contemporary product, why not CALL Gibson and ask them? Hey, what are the wire colors for this GA42 power tranny?

What does an ohm meter say? If I were guessing - and this may be off the wall - I'd assume black to blue was one primary, then Black/white to Blue/white was the other. They would be paralleled black with black/white and blue with blue/white. I would suspect than that the whiote wire was the lonesome 100v tap. In any event, verify which wires have continuity with each other. Then take resistance readings. If black and blue are associated and they measure 100 ohms (making that number up for example), then see if the ones with white stripe also measure 100 ohms. If one set measures 100 ohms, take the set the white wire connects into and see if it measres something like 80 ohms to one wire and 20 ohms to the other in that set. If so, that makes it the 100v tap.

That assumes the transformer matches the schematic. Gibson traditionally was famous for five versions of the same amp and none matching the schematic. But that was from 20-40 years ago. I would not be surprised of some changes sneak in as production rolls along, bit I wouldn't expect wholesale changes very often these days.

If the transformer does not match the drawing, the lone white wire for instance could be a frame ground. In that case, it would not measure continuity with ANY other wire, but would measure to the frame.