Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently May Fri 29, 2020 5:22 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 8 posts ] 
Author Message
 Post subject: Universal Electronics Power Supply Documentation? Help!
PostPosted: Mar Fri 31, 2017 3:52 pm 
Member
User avatar

Joined: Jan Fri 11, 2013 3:47 pm
Posts: 1311
Location: Camino, California
I acquired this lovely Universal Electronics Model 520a regulated power supply for free. It's got a couple of under-chassis issues, so I've been snooping around online for documentation, but have hit a brick wall. It's an incredibly well-built unit, so I definitely want to get it going. The fellow I got it from was going to part it out for the iron, if you can imagine that! Thanks in advance for any help!

Image

_________________
Watch out!!! I've been known to use...."Jargon"!


Top
 Profile  
 
 Post subject: Re: Universal Electronics Power Supply Documentation? Help!
PostPosted: Mar Sun 29, 2020 2:54 am 
Member
User avatar

Joined: Jan Fri 11, 2013 3:47 pm
Posts: 1311
Location: Camino, California
BUMP!

Still looking for documentation. Spent an hour tracing out a schematic, and realized it's just too big of a job...I'd lose my mind. Can anybody help with a schematic?

_________________
Watch out!!! I've been known to use...."Jargon"!


Top
 Profile  
 
 Post subject: Re: Universal Electronics Power Supply Documentation? Help!
PostPosted: Mar Sun 29, 2020 4:42 am 
Member

Joined: Jan Tue 10, 2012 8:39 am
Posts: 1212
I have a similar unit, the Dressen-Barnes 62-117. It uses a variac and a batch of power tubes in parallel as series pass elements to make regulated power.

In fact, mine is two units in one. 0 - 300V and 0 - 500V and you can put the two in series for 0 - 800V. The high voltage one is rated a few hundred mA and the low voltage half that. Mine has variable filament supply but no bias. You can reverse the polarity of the 300V side to get a negative voltage.

Nice unit but I've never used it. I have a schematic but it's a big one, too big to scan.

Bob


Top
 Profile  
 
 Post subject: Re: Universal Electronics Power Supply Documentation? Help!
PostPosted: Mar Sun 29, 2020 5:49 pm 
Member
User avatar

Joined: Jan Fri 11, 2013 3:47 pm
Posts: 1311
Location: Camino, California
Yes, your unit sounds very similar in general design. Mine uses large Triad power transformers and chokes, and 5881 tubes as the pass elements. It looks to have had some modifications or repairs done under the chassis, as there is evidence of wires having been cut and/or replaced. The iron looks to be good, so I may just have to power it up and see what happens if some documentation can't be sourced.

_________________
Watch out!!! I've been known to use...."Jargon"!


Top
 Profile  
 
 Post subject: Re: Universal Electronics Power Supply Documentation? Help!
PostPosted: Mar Sun 29, 2020 6:10 pm 
Member

Joined: Jan Tue 10, 2012 8:39 am
Posts: 1212
You mean you haven't plugged it in yet? Such self control.

The worst that could happen would be bad capacitors. That's what fuses are for.

Oh, and mine had an intermittent meter switch that caused the output to fail. Just a simple toggle switch. It needed exercising, not replacement.

Bob


Top
 Profile  
 
 Post subject: Re: Universal Electronics Power Supply Documentation? Help!
PostPosted: Apr Wed 01, 2020 2:51 am 
Member
User avatar

Joined: Jan Fri 11, 2013 3:47 pm
Posts: 1311
Location: Camino, California
Well, I cleaned it, cleaned all of the tube sockets and populated it with tubes (8 tubes: 3 5881s, a 5R4, a 5Y3, a 6SH7 a 0D3 and a 0C3...amazed that I had them all on hand) and gave it a smoke test.
The HV came up fine, and seems to work, but I didn't test the regulation with a load just yet. The bias supply is dead, though. I may just backtrace from the bias voltage jack on the front panel, and see what I can uncover without having to trace out the whole circuit. The bias supply adjust is done through one of those A&B pots that are notorious for gumming up with age. It could be to blame. Will keep y'all posted.

_________________
Watch out!!! I've been known to use...."Jargon"!


Top
 Profile  
 
 Post subject: Re: Universal Electronics Power Supply Documentation? Help!
PostPosted: Apr Wed 01, 2020 3:44 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3594
Location: Seattle WA US
Suggest you focus on the bias supply first. In many regulated tube power supplies, the bias supply provides internal bias voltages as well as the bias output.

There is much info on regulated tube supplies in Electronic Instruments, Vol 21 of the MIT Rad Lab series.
https://forum.allaboutcircuits.com/thre ... fs.132329/

-Chuck


Top
 Profile  
 
 Post subject: Re: Universal Electronics Power Supply Documentation? Help!
PostPosted: Apr Fri 03, 2020 3:11 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5688
Location: Rochester NY USA
This one might have a completely separate bias supply (since there are two VR tubes). Bias supply is usually just a rectifier and 150V VR tube, then the pot.

Or it may be similar to say Heath PS-4, which used two VR tubes.

_________________
My web page: https://bit.ly/2rxq4qx


Top
 Profile  
 
Post New Topic Post Reply  [ 8 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: Findm-Keepm, Macrohenry, Majestic-12 [Bot], OldRestorer and 9 guests



Search for:
Jump to:  


































-->


Privacy Policy :: Powered by phpBB