Stand-up PT for 100W Dumble?

[Gaz]

Does anyone have any recommendations for stand-up style PT that'll spit out Dumble voltages? Thanks!

-Alex

[M Fowler]

6L6 or EL34?

I am using an Edcor PT on lower voltage tubes up Dumble build right now but also Heyboer can wind one for you.

www.rjguitars.net has higher voltage trannies in stock now.

Troide has a universal PT 100w that will work.

[ER]

I like edcor XPWR127-120, has a 12v 500mA tap for relays and 7.5A on the heaters if you want to run EL34s. 690v 400mA center tapped (345-60-0-345) with 60v bias.

[Gaz]

Sorry for the late reply, and thanks for the advice?

About the Edcor XPWR127-120, wouldn't the HV be too high at around 480vdc? My understanding is that the Edcor lists the loaded voltages.

Thanks.

[jaysg]

OTS 100W Marshall...think they're called MPT-100.

[Luthierwnc]

Gaz,

That PT puts you right around 450-460 VDC on the plates for a 100 watter. Lots of us use (and recommend) the Duncanamps Power Supply Utility.

http://duncanamps.com/psud2/index.html

Just plug in your numbers and components and you get free, instant calculations. In this case, you have 4 (I'm guessing) 6L6s at 450 volts. They are drawing 34ma each at idle so lets bump that to 160 ma for the quad at operating levels plus the 12AX7s. Divide the volts by the amps and you get 2k8 ohms of load. That's the number you put in at R1. Be sure to change the rectifier to a full-wave. You are looking for the voltage at R1. sh

[Structo]

Does Edcor make any lay down type power transformers?

[Gaz]

Structo, I'm sorry, but you are most absolutely high-jacking this stand-up PT thread! Down with laydowns!

[Gaz]

And thanks Luthierwnc, but I though the Edcor voltages were already loaded. So I just did 345 * 1.4 to get the DC voltage. But if you've used this PT, I obviously believe you, but am just confused about why Edcor says they use the loaded figures?

[Luthierwnc]

I've used and liked Edcor stuff. They would be the ones to straighten-out any questions about how their PTs work under load.

There is a lot of detail on the rail both in the discussion and files. Practically speaking, you are going to get between 1.2 and 1.3 times one of the HV taps to DC. 1.41 is theoretical but I haven't seen it. Replacement twin iron (which works great, BTW) comes stock at around 700VCT. In the day it was 320 a side but going from 110 to 122 wall voltage puts you right back at 700.

I'm planning to get 460ish with these babies. Hope I don't have to carry it very far. sh