1963 Ampeg B15N power transformer help

[boroman]

I have on my workbench 63 B15N
It has unusual, but original transformer windings. I have never seen another like that

Usually it has taps for HV, 6.3V, 5V, but this one has also blue/white, black/white and blue taps (see pic). I managed to check that black/white is the main voltage tap (on every other B15N its just black one but here we dont have any black). But is there any way to check if others are - for example 220-240V taps? I'm in europe, so having 240V tap would be cool!

I havent found any schematics with wire color codes.

[Jon Snell]

We normally find they are either 240volt or 120volt.
Put the amplifier on your variac and measure the HT voltage at the 120v setting. You are looking for 440volts ish. If it is low or not there, it is a 240volt version, otherwise 120volt and will require a 100v/A auto transformer.
If you have already unwired the primary then you will have fun working out what goes where. Put ist back as it was and run the test.
I have not seen an original transformer with striped PVC wires. They were all single colour, not striped.
Could it be a new transformer in the old bells?
Sometimes there is a mains voltage stated on the rear board.

[g1]

The B15S had 240V option. The wiring for 120V is not clear from the diagram. Usually both primary's are paralleled for 120V
To me, the attached drawing looks like it's wired for 240V.

[boroman]

We normally find they are either 240volt or 120volt.
Put the amplifier on your variac and measure the HT voltage at the 120v setting. You are looking for 440volts ish. If it is low or not there, it is a 240volt version, otherwise 120volt and will require a 100v/A auto transformer.
If you have already unwired the primary then you will have fun working out what goes where. Put ist back as it was and run the test.
I have not seen an original transformer with striped PVC wires. They were all single colour, not striped.
Could it be a new transformer in the old bells?
Sometimes there is a mains voltage stated on the rear board.

It's deafinitely 120V and blk/wh is the tap for 120V and all correct voltages are right
The amp, when I got it, had blue and blue/wh wires taped, unconnected (hanging freely)
So just asking if there's anything I can do to check?
Transformer looks stock original, made with black goo inside and old looking (correct gauge and color and "vibe") wires

[boroman]

The B15S had 240V option. The wiring for 120V is not clear from the diagram. Usually both primary's are paralleled for 120V
To me, the attached drawing looks like it's wired for 240V.

I thought about that, but it does not use rectifier tube, and I have here 5V taps too... so weird..

But, If we say its okay to follow the B15S diagram,


The blk + blk-white I have now for 120V is correct, right?

So, for 240V I need to join blk + blue wh? and connet mains between blk/wh + blue??

[g1]

Yes and yes.

[Jon Snell]

Fit a three core mains lead and plug and remove C32 before it bites you. They don't like 240volt mains!
If P.L. is a neon, it will quickly fail with 240v across it, wire an 82k 1/4 W resistor in series with it to match the correct voltage.

[boroman]

Fit a three core mains lead and plug and remove C32 before it bites you. They don't like 240volt mains!
If P.L. is a neon, it will quickly fail with 240v across it, wire an 82k 1/4 W resistor in series with it to match the correct voltage.

I do that withe very B15N that comes to my hands. Cut the death cap and completely remove wiring to polarity switch, but leave it for "the look" only. 63 model has two 6v bulbs to drive the plexiglass etched logo, so no neon lights. And 3-prong cord + new filter caps are always first things I do!

[boroman]

Yes and yes.

That did the trick. I have 240V here! So kind of "rare" I'd say in a 63 B15...

[g1]

That did the trick. I have 240V here! So kind of "rare" I'd say in a 63 B15...

Good stuff. Did you have to change the connections for the bulb, or did it stay connected to the same winding?

[boroman]

Good stuff. Did you have to change the connections for the bulb, or did it stay connected to the same winding?

It's a '1963 model that have two bulbs inside lighting the pleixglass logo. Bulbs are fed from 6,3V so no need to change anything than the primary wiring job like above. Amp was a real mess, goo from caps, dirty, 16/8ohm switches etc. I brought it back to specs today, with new power supply caps, all original conenctions and removed non original stuff. Will be testing everything today... and I need new plexiglass logo!

[loudthud]

If it's convenient, you can wire the neon pilot light to the connection between the two primaries so it only sees 120V.

[Randall]

For what it's worth, I have had those PTs rewound before and re-tarred. So, it is not beyond the possibility it may not be original.