Bipolar PSU or +24V, +48V

OK, I read about 5-6 different threads on this while I was schetching up schemos. I need to make a neve PSU and I wouldn't mind it working as a normal bipolar PSU as well for other uses. So I thought I'd use a 7824 and 7924 to get +-24V and 0, then rewire so the neg rail becomes 0V, 0V becomes +24 and +24V become 48V.. I know this "should" work, but I read a post by PRR where he said

PRR said:

> getting +24 volts and +48 volts from the same supply
Using one bridge as a center-tapped +/-35V, and a +24V and a -24V regulator, and ground moved to -24V, can "work", but is a real mind-bender to wire correctly and debug. Also the 48V sucks across both regulators, and as Jakob found a few months back, certain start-up conditions will pull one regulator "in reverse" and the whole thing locks-up.

Click to expand...

So I tried to re-do keith's PSU without a negative rail and I am not sure if the schematic is correct. I don't know how to attach multiple files so I stuck them all into one image file. They are in order, the bipolar schemo first, then its board layout, and then the redo of Keith's psu and its layout. If anyone could give some clues as to which of these (if either will) work, I'd appreciate it.
Thanks!

i just finished a similar project last night. Only i based it on 2 x lm317. I just took the jlm powersupply and used that a base for a simple single sided etch.

I'll try to post it tonight so we can discuss the differences.

Cool.. yeah I figure the 317/337 would be a bit simpler maybe, but more pieces, so at the same time more complex.. I remember reading somewhere that JLM used a -24 rail as 0V, similar to my first schemo for +24/+48... But I couldn't find it on their site yesterday, so maybe they changed it, or maybe they use the 317,337 and I didn't notice. Will take a look again, but if you could post yours, I'd like to take a look. Thanks!

http://www.jlmaudio.com/ACDCVer2sch.pdf


here's the schemo i based my pcb on. My circuit does +24v and +48v btw.

greets,

Thomas

Cool. Did you use both bridges or one only? Or one and a half?

hi mitsos,

little update i etched my psu and i'm gonna drill it tonight when i come back from work. I'll post my (jlm's butchered) schemo, and pcb art when i confirm it.

ps i used i full bridge for 48v and 1 half for +24,


greetings,

Thomas

cool, thanks.. will be away this weekend, but I'll try to check in to see this..

hi mitsos,

i finally got round to testing my psu-pcb. I got a nice bag of 1000uF panasonic caps from a friend so i could finally finish this sucker. Initial testing was disapointing cos i used a 15-0-15 2x7.66A toroid. i thought it would have been enough for at least the 24v output but i only got about 19v Max on the output.

i noticed that there was only about 21v coming out of the rectifier going into the LM317 so i started looking for another transformer. Only one i could find in my parts bin was a 6x6V 6x1.5A transformer so i wired it up for 18-0-18 2x4.5A and turned on the power. Now i was getting about 27.5V Max and 55V Max. PERFECT!

schematic i used is this one:


overlay:
http://twin-x.com/groupdiy/displayimage.php?pos=-3113

Pcb:
http://twin-x.com/groupdiy/displayimage.php?pos=-3114

greetings,

Thomas

Thanks!

I love it when people post stuff for home etching.  That's real DIY!