SMPS for B+ from PC PS

[jkeny]

Hi all,
Just saw this article from 2004 showing how to convert a AT PC SMPS to regulated high voltage for use in Tube Power Amp
http://www.siliconchip.com.au/cms/A_102096/article.html

Only problem - you need to pay about $5 for access.

I just did and got the full article with schematics & description of mods

Quote from article:
"The circuit is capable of excellent performance. It maintains full regulation at up to 125W, with ripple at 2V peak-to-peak, or 0.3% at full power. This is quite acceptable, as most of the ripple is at twice the switching frequency (60kHz) and so is inaudible.
The 100Hz hum component is only 0.08%, which shows the excellent regulation of the TL494, since the rectified mains source contains 13% of 100Hz ripple at full power. Over-current protection is retained, with a LED added to indicate when it is active."

Final schematic below.

Has anybody tried this? How well does it work?

John

[jackinnj]

Ping Eva to chime in -- or N-Channel as they are the SMPS guru's

one thing I would be very careful of is the insulation value of the secondary wiring -- this is going to be very high -- and a lot of insulation of the windings on the transformer. specify double insulation on the high voltage side (according to Sanjay Maniktala's "Switching Power Supply Design and Optimization"