Heyboer PT problems...

[Blacktweedplexiface]

I have a new Heyboer 330-0-330 PT that is shorting my high voltage through the 5v filament when rectifier tube is installed. Anyone ever have bad luck like this? I'm fairly new to building amps, but I work in control circuitry and have never had any issues with any other amp builds. My first thought was maybe this transformer had a center tapped 5v winding, but I still get continuity to ground with all center taps lifted. (The orange shield tap had me wondering). I guess I'll send the Transformer back. To bad I ruined a couple 5y3s before I figured it out...

[sluckey]

Does this issue only occur when the 5Y3 is plugged in? If so, the PT is not likely the problem. If the 5v winding has a center tap just tape it off and don't connect it to anything.

but I still get continuity to ground with all center taps lifted

Continuity to ground from what? Is this continuity zero ohms or some other ohm reading.

[Blacktweedplexiface]

Does this issue only occur when the 5Y3 is plugged in? If so, the PT is not likely the problem. If the 5v winding has a center tap just tape it off and don't connect it to anything.

but I still get continuity to ground with all center taps lifted

Continuity to ground from what? Is this continuity zero ohms or some other ohm reading.

Yes, the high dc voltage only shorts with the rectifier tube plugged in. There is no 5v center tap. The continuity is from the 5v secondary. 0.5 ohms. Almost acting as if there is a grounded center tap. The 5v secondary should read infinity ohms to ground, no?

[sluckey]

The 5v secondary should read infinity ohms to ground, no?

When in circuit it should read pretty high, certainly not .5Ω. Disconnect both yellow wires from the tube socket and check each wire for resistance to chassis. Resistance should be infinity. If still have resistance, then PT is bad.. But if you now measure infinity, you should look for a short on the B+ rail, probably at the first node.

[Blacktweedplexiface]

The 5v secondary should read infinity ohms to ground, no?

When in circuit it should read pretty high, certainly not .5Ω. Disconnect both yellow wires from the tube socket and check each wire for resistance to chassis. Resistance should be infinity. If still have resistance, then PT is bad.. But if you now measure infinity, you should look for a short on the B+ rail, probably at the first node.

Yes, unhooked from the socket the 5v reads .5 ohm. The b+ is not yet wired to my rectifier socket.

[Phil_S]

Yes, unhooked from the socket the 5v reads .5 ohm. The b+ is not yet wired to my rectifier socket.

I just checked a PT that I have on the bone pile. It has two 6.3V windings and one 5V winding. The all meter at 0.1Ω or 0.2Ω. By that reckoning, 0.5Ω seems high.

Having bothered to unwind a PT one time, I know that the number of turns on the low voltage filament windings are very few, maybe 15-18 turns. It's short length of fat gauge.

Some meters have difficulty with an accurate reading at such low Ohms. One thing you can do that might improve accuracy is to place a small value resistor in series with the winding -- something between 1Ω and 10Ω. That way you might get your meter into a range that it can more accurately detect the low Ohms of the winding.

I would be surprised if it is the PT. I tend to agree with Sluckey. There is a wiring issue. It wouldn't hurt to contact Heyboer, let them know your are having a problem, and ask them how much DCR to expect on each winding. They should be willing to tell you.

Meanwhile, you might also post some pictures of your work. Maybe someone will see something. You keep looking at it and seeing the same thing. This is a sort of fatigue that sets in. Other eyes will give it a fresh look.

[sluckey]

He's not saying he measures .5Ω between yellow wires. He's measuring .5Ω from each yellow wire to chassis, even with the yellow wires disconnected. That indicates the yellow wires are shorted to the PT core.

If he is indeed measuring between the yellow wires then he is not understanding what I asked him to do.

[Phil_S]

Egad, continuity between the yellow wires and the chassis? I hadn't imagined such a thing. I agree it's shorted. That's a bad PT. Let's punish it.

Seriously, if purchased new, I'd expect Heyboer will remedy the situation. Maybe if he asks nicely, they will compensate him for the blown rectifiers, too?

[Blacktweedplexiface]

Egad, continuity between the yellow wires and the chassis? I hadn't imagined such a thing. I agree it's shorted. That's a bad PT. Let's punish it.

Seriously, if purchased new, I'd expect Heyboer will remedy the situation. Maybe if he asks nicely, they will compensate him for the blown rectifiers, too?

Yes that is from the 5v secondary to ground. Between the yellow wires is the normal .1 ohm and still puts out 5 volts, but as soon as the rectifier tube is plugged in it shorts my B+ to ground through the 5v winding. I'll ask about compensation for the rectifier tubes, but I won't hold my breath. I have a new transformer on the way.

[The Ballzz]

I have a couple questions/requests:

> Can we see a wiring diagram for the transformer?
> Which transformer wire is actually connected to the chassis, or is the only ground connection through the frame of said transformer?

Just Curious?
Gene

[Blacktweedplexiface]

I have a couple questions/requests:

> Can we see a wiring diagram for the transformer?
> Which transformer wire is actually connected to the chassis, or is the only ground connection through the frame of said transformer?

Just Curious?
Gene

I dont have the diagram I'm front of me right now but it's nothing out of the ordinary. It's actually a David Allen pt that he has heyboer build. The Tp40h. And the grounding is through the transformer frame to the chassis. I lifted all center taps and other windings to be sure. David sent me another transformer already so he is being very helpful.

[Phil_S]

David sent me another transformer already so he is being very helpful.

That sounds like a very good result!

[Blacktweedplexiface]

Well my new transformer worked out great. I even tried out the B+ on my thumb! Thank you all for the input.