power transformer bad?

[The Dude]

I'm sorry for being such a newbie, Juan. Short and long, I'm using the PT and OT from a jtm60 in a jcm800.

Understood, but we need to know what sort of rectifier arrangement you came up with. A schematic would be most helpful. Since you have no HT CT, you must have done something different. The schematic doesn't have to be anything fancy. Just draw up your PS as you have it and upload it. It's nearly impossible to help you without knowing what circuit you are working with.

[TarheelTechinTraining]

I hope this is right

[The Dude]

......and that bridge rectifier/cap circuit is hooked to the 380V tap of the transformer each end of winding to an AC input of the bridge (where the little squigglies are )?

We also need to know how your primary is wired. You have two windings. are they series, parallel, other. Can you draw how you have the primary configured?

[TarheelTechinTraining]

that's l[ATTACH=CONFIG]33380[/ATTACH line voltage and neutral

[The Dude]

This may be some helpful reading. At any rate, it looks like you've got the HT part working, albeit pretty high voltage.

http://www.hammondmfg.com/pdf/5c007.pdf

[TarheelTechinTraining]

Thanks, Dude. How can I tame the B+ voltage?

[TarheelTechinTraining]

is this right for the bias ?

[Chuck H]

I'm a little confused about how this happened at all when the rectifier type/voltage confusions/center taps/transformer specifics/request for actual schematics/etc. has already been covered in the other thread about this project. Same problems, same answers, new thread inside of a week?

I'm glad it's working. Circuit and voltages seem correct now. The JTM60's have a VP of 480+. You'll need sturdy tubes. Especially if you plan to drive them into clipping.

[TarheelTechinTraining]

Sorry for the rehash. I felt I had posted in the wrong place. Plus I finally understood what I very was missing, grounding the bridge.

[loudthud]

[ATTACH=CONFIG]33387[/ATTACH] is this right for the bias ?

No, No, No!

[Chuck H]

[ATTACH=CONFIG]33387[/ATTACH] is this right for the bias ?

We can demonstrate how to implement the bridge for this circuit, but even then you may not get the bias voltage you need from the 43V winding. You'll probably need to use a voltage doubler rectification.

[Chuck H]

Do not wire up the circuit you posted.

A little simulating and it looks like you could get about -39v to -53V from the bridge circuit if you do it like this instead:

[g1]

You'll probably need to use a voltage doubler rectification.

If you look at the jtm600 diagram, you'll see this is the case. If there were a better option, I think they would have used it.

[Chuck H]

If you look at the jtm600 diagram, you'll see this is the case. If there were a better option, I think they would have used it.

One observation is that the JTM600 circuit seems to be regulated to 51V with a zener. I think the bridge circuit I posted above would actually provide just as much if not a tad more. Maybe not a bad thing with modern tubes. I'm using a pair of Ruby EL34B's and IIRC the bias is something like -47V with 470Vp. Considering the component count and difficulty of either circuit I think the bridge option might be easier too. Then again, I made up the circuit above and the one originally used with that PT is tried and proven. Not that I have any doubts about my circuit

EDIT: Looking at the JTM600 circuit again, it doesn't look like a voltage doubler to me.?. It looks rather like a complicated cousin of the one I posted.

[TarheelTechinTraining]

I've implemented the changes to my bias, thanks to Chuck.Though I can only get -56 to -42 for bias.