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Strange double-voltage output on Power One supply?
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Strange double-voltage output on Power One supply?
tapauly
Hi all,

I recently wired up an HCC-15-3-AG power supply I purchased off Bel Power's licensed surplus reseller, and I'm having an odd issue. The transformer is wired for standard use in the US, with 120 VAC 60 Hz input; legs 1 & 3 are shorted, as well as legs 2 & 4, with AC applied to 1 and 4. The negative output is measuring the expected -12 V, but the positive leg is showing as 23.96 V! This is well beyond the trimmer's ability to re-calibrate, so I'm wondering if this sounds like an obvious fix/part issue or if I need to do a deeper examination, i.e. talk to the distributor.
search64
Just to doublecheck: is it possible you’re measuring between the negative and positive the second time? That would give you a voltage of 24v.
tapauly
Good thinking, but no, both voltages were measured as (+/-) OUT against the COM ground.
guest
if you are measuring 24V at the powersupply output (supposedly regulated), then it is either busted, or there is something wrong with the measurement. for the latter, are you using the right "ground". on some powersupplies, the thing labeled as ground is earth ground, and there is a different post for the reference rail. this one also has remote sense leads, and maybe those need to be strapped? typically not, but its a possibility. if all of that seems ok, id contact the seller and let them know.
sduck
return it ASAP.
nimmen
Looks wrong/bad and beyond trimmer range, have 3x of very similar PSUs and never reached such high voltages.
tapauly
FWIW, Radwell tech suggested connecting the sense leads to the outputs as a fix, but it was a no go. Refund and purchased replacement on the way...
EATyourGUITAR
I know how to fix these but only if it is what I think it is. They sell for $15 on eBay. Just get another one. If I were you, I would have kept it as a side project. A right proper challenge to reverse engineer and troubleshoot. One failed resistor or one failed solder joint can cause this behavior. It is not regulating off the reference on the trimmer. Either the reference is not correct or the regulator is failing disconnected etc.. both of these problems are fairly simple to identify. You have a working copy of the circuit on the other channel.
tapauly
To be clear, I received a refund but did not have to return the faulty unit. I plan to attempt a fix when I have more free time, but for the time being I'd rather be putting the synth together than troubleshooting a power supply under warranty!
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