skyboltone wrote:Hey Moose. I guess I went wrong on trusting the schematic on the Liverpool then. I always thought that somebody had mesured 235-0-235 on one so that's what I bought. Where did the 260 come from? What are we looking for on the plates of a Liverpool?
The 331V for B+1 and the 234V over the PT have probably come forward from the original Mark Abbot material. Many years ago he did a lot of research and exchanged a lot of letters and cobbled together all that information for us, but it was just that. Pieced together from a lot of sources.
I'm not sure where the measurements came on the liverpool, but something isn't kosher with the 234 written on the schematic. I think those numbers were either someone's mistaken math (it could be possible someone did the calculation with ideal numbers and just guessed at the 234 written there) or they were one of the early rumors that got perpetuated. But they have to be wrong. Let me explain.
First, B+ on those things is like 335V, 340V, or something like that. Hot AC30 range.
Second, the B+ value written on the last posted schematic I saw was 331V.
So, let's begin with this problem. The normal full-wave rectifier, under ideal conditions with no load and no losses, would produce 1.414 times the secondary.
234 * 1.414 = 327.6
235 * 1.414 = 332.3
So, you're only getting that 330V in an ideal world with zero load. So, what's written on the schematic for B+ voltage does not match that 234V number already. However, I can see how someone did a quick divide by 1.4 and came up with the 234V figure. That's my guess at how that 234 made it to the schematic.
Anyway, in the real world you see a drop in voltage based on plate draw, resistance in windings in the PT, volt and a half drop for each pair of diodes, resistance across the OT windings (assuming the measurement is at the plate) etc., and the magic of Ohms Law.
So, the theoretical output of a 260-0-260 is around 365V (260*1.4 = 364) -- take away 25V for all the silly inefficiency of wire and diodes and such, and you're under 340V B+.
That's all a batch of logical guessing where it comes to what's written on that schematic, but the transformers from KFs line cards, including transformers he used in his production liverpools, are 260-0-260 (for the 120V primary, or the rough equivalent for the 115V primary). This isn't a secret, and Allyn's built zillions of these things with the Pacific tranny of the same voltage range. Pictures that popped up on fleabay of a liverpool even had the same PT part number from the linecard -- which is the same both for Pacific pool trannies and heyboer's dual tap trannies, incidentally.
The earliest liverpools might be different as Ginger didn't use a heyboer or pacific tranny, for instance. But anecdotal evidence is that Ginger's still in a similar voltage range.
In other words, we're pretty darned sure about these secondary voltages, and 235V ain't even in the ballpark.
That said, I don't think an amp running El84s at 300-310V would sound bad. It might even provide the benefit of a little more grind at slightly less power for the more rock and roll oriented among us, just as VVR does. Even if it isn't the same as a production 'pool, if you dig what you built, what you built is good.
