Hammond 370BX shorted?

[Esquirefreak]

Hey, everyone!

Just hooked up a Hammond 370BX PT for a 5F2A build and while the alternating voltages looked fine, I get the feeling that something is shorting BIG TIME. I measured voltages before putting the rectifier in. No other tubes in the amp except for the recto (Brimar 5Y3);

HT: 311.4 VAC - 0 - 311.5 VAC

5V: 2.85 VAC - 0 - 2.83 VAC

6.3V: 3.55 VAC - 0 - 3.55 VAC.

I put the rectifier in and noticed that I had basically zero B+ voltage. And just when I reached for the power switch there was an arc in the recto tube. The tranny was noticably warm (warmer than it should be, considering the circumstances).

For what it's worth I've tried both the 230v and 240v hookup on the primary side, whereas the 240v came up a little short on the voltages.

Could one of the filament windings possibly be shorted? I bought the tranny blind sighted and have no proof of it actually functioning.

I measured resistance across the windings;

HT:   250Ω / 250Ω

5V:      .4Ω / .4Ω

6.3V:   .5Ω / .5Ω

The amp itself worked flawlessly when using the previous PT (Hammond 290CAX).

All help is greatly appreciated.

/Max

[sluckey]

Did you connect the YEL/BLK wire to ground? If so, don't do that because that puts a dead short on the B+ to ground. You must tape off that YEL/BLK wire unless you know how to properly use it.

     https://www.hammfg.com/files/parts/pdf/370BX.pdf

[Esquirefreak]

Oh, sh*t... That's probably it...

Since I have resistance between the leads I'm really hoping that I didn't fry it.

Thank u, Sluckey!

What's the 5v CT intended for, or rather, how should it be used?

/Max

[sluckey]

What's the 5v CT intended for, or rather, how should it be used?

Rather than connecting pin 8 to the B+ filter caps, you can just connect that center tap to the B+ filter caps.

PT is probably fine. Rectifier tube may be questionable now.

[Esquirefreak]

Got it, thanks for explaining!

/Max