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Old 06-21-2021, 06:06 AM   #1
Pimpom
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Default Does anyone have the schematic of a Tagan BZ700 PSU?

Does anyone happen to have a circuit diagram (schematic) of a Tagan BZ700 PSU that they can share? I searched but had no luck.

One of two MOSFETs in the PFC circuit blew about 5 years ago. Not having the exact type, I replaced both with a similar type and it's been running fine, 10-16 hours a day every day, until one blew again last month. On both occasions, the transistor blew when there was a severe power fluctuation and the UPS kicked in and out in rapid succession.

The first time it happened, the PSU simply became inoperative. This time it took out the fuse in my UPS along with it. I replaced the transistors again but the PSU stays dead (but no longer shorted).

If this had happened 20 years ago, I'd have simply traced the circuit and drawn the diagram, but my eyes aren't up to it anymore and, frankly, I've become lazier with age (I'll be 70 in a few months). You know how congested PSU PCBs are. Can anyone please help?
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Old 06-21-2021, 06:40 AM   #2
stj
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Default Re: Does anyone have the schematic of a Tagan BZ700 PSU?

5 years for PFC is pretty good - i'd say your transistor choice was o.k.
your primary capacitor is probably trashed though - PFC kills them and the fact that it couldnt smooth over the transition to the ups is a givaway.
check the pfc diode too.
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Old 06-21-2021, 06:58 AM   #3
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Default Re: Does anyone have the schematic of a Tagan BZ700 PSU?

Thanks for the reply. I'll check the main cap, but I'd really like to dig deeper into the circuit. I'm a pro - semi-retired now - in electronics and not wanting to trash this PSU isn't just a matter of money.
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Old 06-21-2021, 08:22 AM   #4
stj
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Default Re: Does anyone have the schematic of a Tagan BZ700 PSU?

get datasheets for any chips you see.
they often have example schematics that match the board.
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