My build is going to make use of a salvage chassis and cabinet, and possibly salvage iron, all from a Univox U1086. The power trannie specs are:
High voltage : 250V-0-250V @ 400mA
Heaters : (two taps) 6V @ 4A and 6V @ 2A
Bias supply : 50V @ 100mA
(I am assuming that I would ignore the bias supply tap since the Express does this differently. )
I figured I would give my trannie a try, but could certainly buyu Moose's stuff as my backup plan.
I see that his PT has two voltages - 300 and 260. Which is the appropriate voltage for the Express? The schematic I found for the Kelly build shows 585V (about 292V per side), so I thought maybe 300 was the corret choice, but then I saw a posting about the Ceriatone trannies,a nd I think it stated that 260V was correct.
Do you think my power trannie might be OK?
Thanks,
Steve
Express trannie help needed
Moderators: pompeiisneaks, Colossal
Re: Express trannie help needed
Steve
The 260v taps on Moose's trannys is for running El84s like in the Liverpool and Rocket. The 300 is for the Express which uses El34s. 260v will get you in the ballpark of 310 - 340v B+ and the 300 will get you in the 380- 400v range. The 250 you have would probably work for a Liverpool/Rocket. What was the Univox running originally? You can't go wrong with Mooses trannys.
The 260v taps on Moose's trannys is for running El84s like in the Liverpool and Rocket. The 300 is for the Express which uses El34s. 260v will get you in the ballpark of 310 - 340v B+ and the 300 will get you in the 380- 400v range. The 250 you have would probably work for a Liverpool/Rocket. What was the Univox running originally? You can't go wrong with Mooses trannys.
Re: Express trannie help needed
You could build a pretty kick-ass 4xEL84 amp with fixed bias running 330V or so... Sort of a slightly more express-like liverpool. And if you rectify the 50V tap and you'll be able to use a lower wattage R to pull the bias voltage into a reasonable range, and the rest of the bias circuit is the same, so it's worth using. Also, a switch to go cathode/fixed bias is easy to rig so you could make it a regular liverpool with one flick of a switch.
Actually, there's a LOT you could build with that tranny, you just won't be able to put out the 400V B+ expresses run at. So, it isn't an express tranny, but it's definitely good iron and shouldn't go to waste.
Maybe a Class A KT-66 poweramp! Run it into an 8K primary and keep the screens under 300V and you should be able to get 25-30 watts.
Or a super-deluxe. You could run 4 6V6 fixed or cathode biased off that thing.
Actually, there's a LOT you could build with that tranny, you just won't be able to put out the 400V B+ expresses run at. So, it isn't an express tranny, but it's definitely good iron and shouldn't go to waste.
Maybe a Class A KT-66 poweramp! Run it into an 8K primary and keep the screens under 300V and you should be able to get 25-30 watts.
Or a super-deluxe. You could run 4 6V6 fixed or cathode biased off that thing.
Re: Express trannie help needed
Well, then, it looks like I will buying some new trannies afterall. I am defintely more interested in building an Express than a Pool-like amp at this time. But I'll deal with the trannies a little later on, as I get closer to completion. I have some chassis renovation to do, and then the board, and the chassis wiring, etc. Moose - I'll be in touch.
The Univox is a PA actually, although its schematic is almost exactly like the guitar heads from the same product line. It runs 4x6L6's, and 4x12ax7 and 2x12au7's.
Interesting thing is that the Univox sees around 700V on the plates! Yes, that is not a misprint. The power supply design results in a very high B+ for such a low voltage PT. I suppose if I were an expert in power supply design I could probably get it to around 400V - but I am not
Luckily, since the original trannies are stand up style, the chassis won't have any big ugly holes in it where the removed trannies used to be. And of course they will stay on the shelf for some future build.
Thanks all!
Steve
The Univox is a PA actually, although its schematic is almost exactly like the guitar heads from the same product line. It runs 4x6L6's, and 4x12ax7 and 2x12au7's.
Interesting thing is that the Univox sees around 700V on the plates! Yes, that is not a misprint. The power supply design results in a very high B+ for such a low voltage PT. I suppose if I were an expert in power supply design I could probably get it to around 400V - but I am not
Luckily, since the original trannies are stand up style, the chassis won't have any big ugly holes in it where the removed trannies used to be. And of course they will stay on the shelf for some future build.
Thanks all!
Steve