YCV50 PT DC Heater Circuit

[ncusack]

Hello,

I a have a set of transformers from a YCV50 I'm looking to build a Trainwreck out of. The PT specs are 0-300V @0.2A,0-6.3V @3A and 0-28V @0.2A. On the YCV40 they use a bridge rectifier on the 28V tap and a 24V LDO to get 24V DC for the SS reverb and run the rectified3 28V through 2 parallel 100ohm resistors in series with the two preamp tubes heaters. By my calcs that would be 28v x 1.4 = 39.2VDC less 15VDC from across the resistors leaving 24.2V for the two preamp tubes at 12V each.

Now since I plan to build an Express amp and only need the DC heaters for two preamp tubes before the PI could I just use an artificial center tap on the 0-28V tap and fullwave rectify and regulate with a 12V LDO (7812)? I like the idea of parallel heaters instead of the series heaters the YCV50 uses. I am also curious about lead dress with the DC heaters in an express build.

If anyone can confirm my thinking or provide any other thoughts it would be great.

Cheers,

Neill

[sluckey]

The idea of artificial center tap on the 0-28V tap and fullwave rectifier won't work. And the two parallel 12v filaments would want 300mA but the PT only has 200mA rating. I think the YCV40 plan is a better choice.

[martin manning]

S Luckey is right- you may not have enough current available on the 28V winding, since you will be asking about twice as much current as it was providing originally. To be safe, I would do exactly as the Traynor schematic. Do not add an artificial center tap when using a FWB rectifier.