Floating supply question.

[Diabolical Artificer]

Thanks Argus for the info. Pretty sure (100%) the tfmr was designed for 50hz as I wound it myself, hence why I have some of the problem's. I bought a tfmr off ebay which was wound for a big transistor amplifier, took off the secondaries leaving the primary and wound on new secs. I got most of it right.

After some thought and measuring of it's twin, I followed Trevor's suggestion of converting it to 6.3v, which is working ok. That left me with another problem, the PSU also has to power a 12v fan. No worries, I get nearly 12v pre the LM317.

I tested the windings output capacity by loading it with decreasing value's of resistors and found it can supply 1.5A, at a push. So it will be able to supply three ECC** triodes, EG 1 ECC82 and 1/2 a ECC83 = 450mA + the fan at 150mA.

The 18.9v winding falling to 9v with the 12v PSU as a load is a puzzle, it can power 3 EL34 heaters and only falls a few 10's of mV to 18.4v. I can live with that, each EL34 is short by 170mV, not too drastic.

A.

[Al (astral highway)]

Originally Posted by Diabolical Artificer

That left me with another problem, the PSU also has to power a 12v fan.

Andy, perhaps cull an SMPS for the fan from a junk PC power supply or walwart. It can be completely isolated from your other supplies, so noise isn't an issue.

Originally Posted by Diabolical Artificer

. I can live with that, each EL34 is short by 170mV, not too drastic.

...but also not ideal. Hence my suggestion to not steal power for the heaters for ancillary applications.

[Diabolical Artificer]

I've been raiding my wall wart SMPSU stash Al and have found a few likely candidates.

A.

[Al (astral highway)]

That’s good news , Andy! You will then have comfortably more power for your heaters...