Strange double-voltage output on Power One supply?

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tapauly
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Strange double-voltage output on Power One supply?

Post by tapauly » Sat Sep 07, 2019 11:13 pm

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.

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search64
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Post by search64 » Sun Sep 08, 2019 12:26 am

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.

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tapauly
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Post by tapauly » Sun Sep 08, 2019 8:33 am

Good thinking, but no, both voltages were measured as (+/-) OUT against the COM ground.

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Post by guest » Sun Sep 08, 2019 9:28 am

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.
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sduck
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Post by sduck » Sun Sep 08, 2019 12:48 pm

return it ASAP.
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nimmen
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Post by nimmen » Mon Sep 09, 2019 4:32 am

Looks wrong/bad and beyond trimmer range, have 3x of very similar PSUs and never reached such high voltages.
busy soldering...

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tapauly
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Post by tapauly » Sat Sep 14, 2019 9:31 am

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...

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EATyourGUITAR
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Post by EATyourGUITAR » Sat Sep 14, 2019 10:32 am

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.
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tapauly
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Post by tapauly » Sat Sep 14, 2019 10:40 am

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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