59 RI Bassman power tranny - zero voltage on secondary side

[Bluefinger]

I have rebuilt a non working '59 bassman reissue that had a couple of dubious mods, broken wires and loose solder joints. Since it was in bad shape i ripped out everything and converted it to a point to point amp. Everything is looking fine but I get no voltage on the secondary side. I switsched it on with only the rectifyer installed. Between the white and black/red wires (230V tap) I get the 230 volts AC so the fuse and switch are ok. Across the red wires on the rectifyer I get 0 volts.
The wiring looks ok ... red/yellow is wired to ground, the rectifyer is wired correctly, red/blue is connected to the bias circuit and the unused power taps are isolated off. Could there be any other explaination for this than a defective power tranny? I just want to make sure before i order a new one

thanks!

[The Dude]

Excuse me if this seems a stupid question, but I've no idea about your technical abilities and/or knowledge. You are measuring AC and not DC voltage on the secondary, correct?

[loudthud]

Are the Black/Yellow and Black/Green wires joined? Do you have continuity on the primary?

Schematic link: http://el34world.com/charts/Schemati...N_59_REV_E.pdf

[Tom Phillips]

And tell us if you read voltage on the 6.3V and/or the 5V secondary windings.
If yes, and you still get a 0V reading on the high voltage secondary, then it would appear that you have a defective transformer.
Edit: In that case I would expect that a resistance reading of the high voltage secondary, with the unit powered off and all filter caps drained of course, would show an open circuit.

[Bluefinger]

Yes. AC

[Bluefinger]

No, they are isolated off separately

[Enzo]

Can we be more specific what we are answering?

Is the primary winding open?

[alexradium]

sometimes there is a thermal fuse hidden in the tranny bobbin,i'd try to remove the tape and look for it.

[olddawg]

sometimes there is a thermal fuse hidden in the tranny bobbin,i'd try to remove the tape and look for it.

That's normally on the primary side. In that case the primary side would be open. Check for continuity in the primary.

[loudthud]

Are the Black/Yellow and Black/Green wires joined? Do you have continuity on the primary?

Schematic link: http://el34world.com/charts/Schemati...N_59_REV_E.pdf

No, they are isolated off separately

Can I assume the answer you posted was to my question?

If the Black/Yellow and Black/Green are not connected, it won't work. You can buy a replacement transformer and it still won't work. This is an expensive lesson you seem wanting to learn.

Here's a simple test. Disconnect the Mains plug from the mains. Set your meter to Ohms and connect the two leads to the two pins/blades on the Mains plug that normally supply current to the amp. Switch the amp On. If you are in North America or Japan the meter should read about 35 Ohms. If you are in a country with 210 to 240 Volt Mains, the reading should be about 70 Ohms. If the meter gives an over-range indication, the primary wires of the transformer are not connected properly and the amp won't work until they are. If you can't follow the schematic I linked, say so and someone will walk you through it.

[Bluefinger]

I disconnected the primary side and yes, it's open. I asked the owner and he told me that the amp smelled burnt as it stopped working.... it seems like that tranny is done.

[loudthud]

A burnt smell could have been almost anything, but it is unlikely it was the transformer.

What Mains Voltage are you trying to use?

[Bluefinger]

Can I assume the answer you posted was to my question?

If the Black/Yellow and Black/Green are not connected, it won't work. You can buy a replacement transformer and it still won't work. This is an expensive lesson you seem wanting to learn.

Here's a simple test. Disconnect the Mains plug from the mains. Set your meter to Ohms and connect the two leads to the two pins/blades on the Mains plug that normally supply current to the amp. Switch the amp On. If you are in North America or Japan the meter should read about 35 Ohms. If you are in a country with 210 to 240 Volt Mains, the reading should be about 70 Ohms. If the meter gives an over-range indication, the primary wires of the transformer are not connected properly and the amp won't work until they are. If you can't follow the schematic I linked, say so and someone will walk you through it.

ok, i got it ... this is a funny wiring for a tranny ... Haven't seen something like that before. The ones i have been using use only one tap for the needed voltage and that's it. on this one the coil is interupted.

Still the colors on your diagram do not match the colors on the tranny in this amp completely. There's no violet and no black/white wire. hope the other ones are the same

[Bluefinger]

Can I assume the answer you posted was to my question?

If the Black/Yellow and Black/Green are not connected, it won't work. You can buy a replacement transformer and it still won't work. This is an expensive lesson you seem wanting to learn.

Here's a simple test. Disconnect the Mains plug from the mains. Set your meter to Ohms and connect the two leads to the two pins/blades on the Mains plug that normally supply current to the amp. Switch the amp On. If you are in North America or Japan the meter should read about 35 Ohms. If you are in a country with 210 to 240 Volt Mains, the reading should be about 70 Ohms. If the meter gives an over-range indication, the primary wires of the transformer are not connected properly and the amp won't work until they are. If you can't follow the schematic I linked, say so and someone will walk you through it.

ok, I know what's going on. Of course I get infinite resistance if there are two coils in there that need to be connected with blk/yel + blk/gr. I hope that the color codes are similar to the diagramm. white and black/red was definitely connected to the mains voltage. i wrote that down. Since i never saw an interupted primary winding before I didn't pay the other taps any mind. I assumed that they were all connected to dead ends.

so I'm going to leave black isolated off, connect blk/yel and blk/gr and see what voltage i am getting.

[loudthud]

The attached diagram is from the Rev A schematic. It might be closer to what you have. The transformer part number is 036484.

Again I ask, what Mains Voltage are you trying to use?

As a safety precaution, I suggest you use a "light bulb limiter" (Google it if you don't know what that is) and remove all the tubes until you can power up the amp and measure something close to 6.3VAC on the pilot lamp. A wrong connection on the primary could blow the transformer or a Mains fuse if connections are not right.