Gibson power transformer?

[chuckb]

Hey guys, I have a set of transformers out of a Gibson-45 RVT amplifier. I have the schematic for that amp and I'm having trouble sorting out the windings. On the power trans there's two green (hearter windings),a green/yellow(CT), two RED wires(Rectifier pins 4&6) & a RED/Yellow(CT),not to sure about the Blue 50v wire, or the White wire.Two Black wires (117v).Correct me if I wrong here and I would like to know what the Blue 50vWire and the white wire are for? Shouldn't there be two wires for pins (#2&8) of the rectifier tube also? Would I be able to use these transformers for a Fender Bassman build? The OT is 16ohm.If someone has any specs on theses transformers it would br greatly appreciated.

Chuck.

[52 Bill]

I'd suggest getting the schematic for the Gibson amp and looking at it to see how it was hooked up originally.

Some Gibsons used 6v filament rectifier tubes, so your transformer may not have a set of yellow 5 volt wires. The original amp may also have had a solid state rectifier and therefore no 5 volt winding.

The blue 50 volt tap will be for the bias supply. You need to find out if it is a tap of the high voltage secondary or if it is a separate winding.

Does the white show any continuity to any of the other wires?

[chuckb]

Hey 52 Bill, Here is a link to the schematic. Could you have a look at it and let me know what you think? It does have a solid state rectifier I believe and I do believe the 50v bias tap is a seperate winding.The guy I bought these transformers from said that the PT had a 120v primary,secondary windings=381-0-381 CT HT, 6.3v CT filament, 50v bias tap. The OT was 16ohm secondary tap only and the original output circuit was (2) 6l6GC@453vB+.Can I use these for a Fender Bassman build ? Any help you can give me would be greatly appreciated. The schematic is of poor quality though.


http://http://www.gibson.com/Files/schematics/GA-45RVT.jpg

Chuck.

[chuckb]

Hey 52Bill, the white wire has no continuity with any of the other wires. The 50v bias tap blue wire I believe is a tap off the HT secondary.I did a continuity test on the blue 50v bias tap and the high voltage CT is the only one that reacts to it.

Chuck.

[52 Bill]

I looked at the schematic and the power transformer should be big enough for a bassman type circuit. What version are you looking to build?

The blue bias wire is a tap off of the high voltage secondary.

If the white wire has no continuity to any of the other windings, either primary or secondary, then it is probably an electrostatic shield, so just ground it.

The output transformer is designed for a 16 ohm secondary, as the original amp had 2-8ohm tens wired in series.

With the solid state rectifier, the schematic shows 460vDC of B+. I'd expect that to be a little higher with modern line voltages.

[chuckb]

I'm looking to build the original 59 Tweed Bassman ,though I not sure of the model,ie;536A? Will I need 5v windings if I use a tube rectifier,or is there some other way around it.

Chuck.

[52 Bill]

Yes, you will need the 5vAC winding if you are going to use a tube rectifier.

You could go with solid state rectifier diodes or maybe a Weber CopperCap.

Or you could add a separate filament transformer for the 5 volt winding.

[chuckb]

I have a solid state rectifier I can use,but really would like to use a tube rec. I guess I could get a seperate 5v filament transformer from Mercury Magnetics. Thanks so much for your help I reall appreciate it.

Chuck.

[chuckb]

I have a solid state recitifier that can be used in place of 5u4,5w4,5y3 recitifer tubes . I'm thinking about using this instead of the tube rectifier because I don't have a 5v winding. How do I wire the recitifer tube socket to accomidate this ss rectifier? What pins on the SSrectifier are active? Also do I run the 50v bias tap straight to pins 5 of the power tubes for the 5E6a Bassman circuit?

Chuck.

[52 Bill]

I have a solid state recitifier that can be used in place of 5u4,5w4,5y3 recitifer tubes . How do I wire the recitifer tube socket to accomidate this ss rectifier? What pins on the SSrectifier are active?

The high voltage from the transformer should be wired to pins 4 and 6. The dc output will be at either pin 2 or 8, depending upon how the solid state module was wired. You can check this with the diode test on your meter.

Also do I run the 50v bias tap straight to pins 5 of the power tubes for the 5E6a Bassman circuit?

The bias tap needs to be rectified and filtered just like the original circuit was to produce a negative dc voltage. You will need at least a diode like a 1N4007 and a small filter cap like a 100uF at 100vDC and maybe a resistor or two to set the bias to the correct level.

Please refer to the schematic.

[chuckb]

I already have the high voltage wired up to pins 4&6,and the schematic I'm trying to follow is the 5e6a,which comes with two rectifier tubes.I am referring to the GA-45RVT schematic, but it can be confusing trying to apply the same layout to the 536a circuit.If it were just tube rectifiers with a 5v winding I had to deal with I would be alright. I have never worked with a SS rectifier before. I realize that the bais supply needs to be rectified and filtered. I see now after studing the schmatic futher how I'm to do this.Thank you,I appreciate your help.

Chuck.