Power transformer 340-0-340 or 270-0-270 option?

[tweed]

I have notice that my tweed transformer puts out 340-0-340 (red leads) and 270-0-270 (red an white leds).

Diagram mentions to use the first. It happens that I think the voltages on the rectifier tube pins looks a litle on the high side 388V. It's safe to connect the lower voltage leads?

[Bruce / Mission Amps]

I have notice that my tweed transformer puts out 340-0-340 (red leads) and 270-0-270 (red an white leds).

Diagram mentions to use the first. It happens that I think the voltages on the rectifier tube pins looks a litle on the high side 388V. It's safe to connect the lower voltage leads?

Sure... but your B+ will drop dramatically and your power tubes will be overbiased.
However, are you using a NOS 5Y3GT rectifier? If not, do that first.
If this is my Mission PT or a WeberVST Deluxe PT, the 270v taps were originally for an amp where I was using two EL84s and Weber just copied my specs.
Still, there is no reason you can't run the amp in very low voltage.
Just be prepared to remove the power tube's cathode biasing resistor and replace it with something much lower... like maybe 180-200 ohms, to increase the idle current... etc.
You could also try the 270v taps and a Russian 5Y3GT which is very stiff and it will give you higher B+ then a NOS 5Y3GT.

[tweed]

Sure... but your B+ will drop dramatically and your power tubes will be overbiased.
However, are you using a NOS 5Y3GT rectifier? If not, do that first.
If this is my Mission PT or a WeberVST Deluxe PT, the 270v taps were originally for an amp where I was using two EL84s and Weber just copied my specs.
Still, there is no reason you can't run the amp in very low voltage.
Just be prepared to remove the power tube's cathode biasing resistor and replace it with something much lower... like maybe 180-200 ohms, to increase the idle current... etc.
You could also try the 270v taps and a Russian 5Y3GT which is very stiff and it will give you higher B+ then a NOS 5Y3GT.

Thanks for your reply Bruce!
I am using a RCA 5Y3 and a 270 oms cathode resistor, I have notice that thistube kicks out a lot of voltage comparing wit a diode rectifier. I was thinking in giving a long live to the output tubes.

[tweed]

Other though that is bugging my mind. Let's say that my power transformer has 220V, 230V and 240V taps.

My outlet puts out 220v and my PT secondary puts out 340-0-340, can I use the 230V or 240V tap to brings all voltages down a bit? Does this make any sense?

Tanks! REgards

[Bruce / Mission Amps]

Other though that is bugging my mind. Let's say that my power transformer has 220V, 230V and 240V taps.

My outlet puts out 220v and my PT secondary puts out 340-0-340, can I use the 230V or 240V tap to brings all voltages down a bit? Does this make any sense?

Tanks! REgards

Yes....
340v/220v=1.545:1, 340/230v=1.478:1, 340v/240v=1.4166:1
1.545 x 220v = 340v-0-340v
1.478 x 220v = 325v-0-325v
1.417 x 220v = 312v-0-312v

[tweed]

Yes....
340v/220v=1.545:1, 340/230v=1.478:1, 340v/240v=1.4166:1
1.545 x 220v = 340v-0-340v
1.478 x 220v = 325v-0-325v
1.417 x 220v = 312v-0-312v

Great info!

I see a lot of flexibility here... I am about to move back to Europe and I am studing the best option for my tweed. I will start with the 240V tap and see what happens.

Thanks one more time, Regards

[tweed]

Yes....
340v/220v=1.545:1, 340/230v=1.478:1, 340v/240v=1.4166:1
1.545 x 220v = 340v-0-340v
1.478 x 220v = 325v-0-325v
1.417 x 220v = 312v-0-312v

Hi Bruce, Just one more question, will this affect the filament winding voltage?

[tubeswell]

whatever voltage that is at the primary affects what you get from the secondaries, because the windings are at a ratio. Now some trannies have multiple primary taps or windings that allow you to connect various primary voltages to achieve stated secondary winding voltages.