Supro 88T Schematic / Power Xfmr Specs

[paulcblais]

Looking for a schematic and power transformer specs for a Supro 88T Amplifier. It's got 4 12AX7s and 2 6L6GC, not tube rectified. the power transformer is smoked, Its a triwec T112, EIA 5246607. The HT winding is not center tapped but the heater winding is. There is no 5V winding. I've solved the issue of why it was smoked, power supply recap job that was done poorly. Any help you all can provide would be greatly appreciated.

[shooter]

This schematic shows 320vac secondary if that helps

https://el34world.com/charts/Schematics/files/Supro/Supro_s6688.pdf

compare to a "like" 40-50W Fender/Marshall with same tubes 

[sluckey]

In addition to shooter's info... probably needs 320v @ about 150mA. Shop around for something that satisfies that voltage requirement and will also fit the chassis cutout.

Another option... If I could not find a suitable transformer I'd probably look for a 320-0-320V @150ma, and 6.3V @ 4A. May have extra windings/taps but you can tuck those away. Oh, you would need to replace the FWB rectifier with a conventional full wave rectifier. Easy to do.

[paulcblais]

Awesome! That's exactly what i was thinking also. I'm thinking i'd like to find something in the 200ma range just so it has a little headroom available in the power supply to keep things cool. Edcor has the XPWR124 "640V (320-0-320) at 150mA center tapped, 6.3V (3.15-0-3.15) at 4A center tapped and 5V at 2A." which looks like a perfect fit for $57 plus shipping. They build on order so there's a several week wait time but they have always been reasonably fast in the past. Hammond has a 376X for around $140 or the 276X for around $110 both with 176ma on A 640ct. I've gotta see what the customer wants to do and what he can afford.

[PRR]

> something in the 200ma range

The schem shows just 380V at power tube plates, far short of the expected 330V*1.414= 460V. So I think there is a LOT of sag in that stock PT, and if you run a "better" PT the tubes run 30+% hotter than intended. On paper this happens to be the difference between the 23W Pdiss on the plan and the 30W Pdiss of any modern "6L6"(GC). But it will never be a 5F6a, and goosing from 25W to 30W out won't make you more rich or more famous.

I'd be thinking "36 Watt" PT (big brother to the 18W). Current is close. If wound for silicon rectifier the voltage will be a little low. If wound for a vacuum rect the voltage may be real close.

[DummyLoad]

PSUD2 suggests a 125mA part to achieve similar loading. based on telemetry provided, the output stage is pulling 135mA since 27V/200Ω=135mA flowing through common cathode resistor - guestimated g2 and rest of the preamp loads.

--pete