Mystery power supply...help me identify!

[Eric Rottmayer]

Anyone know?







I was thinking it was maybe a tube mic power supply...but the 4 pin XLR is weird.
I tried some searching and it seems that type of connection was used in powering older video cameras and video gear? Does this look familiar to anyone? Help?

[Nate Dort]

4-pin XLRs are still very common in the sound-for-video/film industry and on video cameras, though the signal-flow gender is reversed from a standard 3-pin audio XLR (i.e. power output is on a female). Get a meter and see if there's power on the 4-pin. Most of the 4-pin powered stuff I've encountered has been 12VDC, wired pin 1 gnd and pin 4 hot.

Looks like it goes to a console of some sort. Probably +/- voltage on the 4-pin and phantom on the 3-pin. The three LED's would reinforce that.

[Nate Dort]

Actually, I bet the red LED is a general on/off status indicator, and the two green LEDs are to show the status of the other voltages. It may just be a single-ended supply voltage and phantom, like an old soundcraft supply or something. Or maybe no phantom at all.

[The Scum]

Any chance you can pop the top, and post some photos of the guts? Depending on the voltage regulators used, they may be a dead giveaway of the voltages involved.

[Eric Rottmayer]

Thanks for taking the time to look and respond...more pics of the guts...looks like a mega huge transformer in the back?













Really I was hoping this was a power supply to some old tube mic that I could hunt down and eventually use. Oh well. :(
Can any of this stuff be re purposed for other audio gear? I'm just starting to solder...
just got a repair bench set up and I've been sort of blindly buying things like this that I might be able to use parts from etc.
Sorry if this is silly...I'm new to this world...but I'm really excited about it and ready to take on some projects and build some amps!

Thanks again...still, if anyone knows any more info about this piece, it would be great appreciated!

E

[The Scum]

Yup, mega huge transformer...the silver cylinders are 28 VDC rated caps from 1978. The transformer is marked 9V...is there an 18V making that's lost in the glare?

In the top photo, it looks like there's a perforated panel you can slide out of some grooves. What's under there? Any silver dome things marked like 78xx or 79xx, or LM317?

[Eric Rottmayer]

YES! Holy crap I didn't even notice that...it says 18V where the glare is on the top and bottom...



UA79HGSC - 8130

UA78HGSC - 8102

EL2479 - 317K

What are those things? Kinda looks like where the tubes would go if it was
tube based. :)

Thanks again.

[The Scum]

Those guys are what I was looking for - the voltage regulators...the ones that actually do the work of being a power supply. They can get hot, so they're bolted to the aluminum extrusion, which acts as a heatsink.

UA79HGSC - 8130
UA78HGSC - 8102
EL2479 - 317K

The good/bad news is that they're all variable regulators - sometimes there's an encoding in the part number of the voltage they regulate (7805 for 5 volts, f'rinstance). Which means we can't tell by looking what the supply is for. But it means they're adjustable, so you can set them to other voltages.

They also update the age of the thing a little - mid 1981.

Here's a datasheet for one of them, others probably on that site:
http://pdf1.alldatasheet.com/datasheet- ... 78HGA.html

So, finally, we can draw some comclustions about what to do with it:
It's a power supply, with 3 adjustable Voltages. Fire it up and measure them. If you're lucky, they'll be in the +/-15-ish range, which is great for analog audio circuits. If you're a little less lucky, they won't be +/-15, but you'll be able to adjust the trimpots inside to get them there. And if you're supremely lucky, the third voltage will be +48V.

So go build some preamps or a modular synth around it.

Or gut it, and use the enclosure for a Nelson Pass Zen power amp. That hefty heatsink stuff will come in handy.

[Eric Rottmayer]

Thanks for your help, patience and responses TS.

I'll measure the voltages and see where it's at.

Yeah...the enclosure is kinda cool. Maybe that's what I get out of it.

Thanks again!

Eric