A4000 PSU go pop : replacement fix

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IanJeffray
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A4000 PSU go pop : replacement fix

Post by IanJeffray »

A4000. "No power". Sure enough, no power. Open the PSU. Measure the fuse - open. Replace the fuse. Power up. BBAAANNGGG!! And a pretty green flash too. And my new glass fuse now has little metal balls in it. Yay.

Hmm ok that's a shame. Now I have to really try and fix it.
IMG_7460.JPG
Those don't look good. Pulled them out. I think the brown stuff may be intentional, but may have helped rot/rust/something at the bottom there. Red Red Red. A pair of 2K2 ? Really? What kinda rating? They both measure the same 32,8K ... Ah it'll be orange orange orange then. 33K. Ok, so these are still fine?

But also...
IMG_7464.JPG
pretty sure that hole's not supposed to be there. Pull it. Reads 8 ohms. Not sure if that's as it should be or not.

Tempted to cut my losses and see if I can wedge another of those nice Meanwell boards in here. I don't like dealing with power electronics. :(
Last edited by IanJeffray on Mon Sep 27, 2021 8:48 pm, edited 1 time in total.
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danielj
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Re: A4000 PSU go pop

Post by danielj »

Meanwell ftw.
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cheshirenoir
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Re: A4000 PSU go pop

Post by cheshirenoir »

I'd try and replace the component.
(if it was me, that'd fail and THEN I'd get a Meanwell :-)

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flaxcottage
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Re: A4000 PSU go pop

Post by flaxcottage »

CJE Micros sell reconditioned A4000 PSUs. When mine went they even had a BNIB one for a very reasonable price.

I know this sounds like an advert but I am in no way affiliated with CJE. :lol:
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IanJeffray
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Re: A4000 PSU go pop

Post by IanJeffray »

flaxcottage wrote:
Thu Sep 23, 2021 9:57 am
CJE Micros sell reconditioned A4000 PSUs. When mine went they even had a BNIB one for a very reasonable price.

I know this sounds like an advert but I am in no way affiliated with CJE. :lol:
£50 new or £45 for used. Vs £25 for the meanwell and some fun making it fit. I already ordered the meanwell ;)
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daveejhitchins
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Re: A4000 PSU go pop

Post by daveejhitchins »

IanJeffray wrote:
Thu Sep 23, 2021 10:56 am
flaxcottage wrote:
Thu Sep 23, 2021 9:57 am
CJE Micros sell reconditioned A4000 PSUs. When mine went they even had a BNIB one for a very reasonable price.

I know this sounds like an advert but I am in no way affiliated with CJE. :lol:
£50 new or £45 for used. Vs £25 for the meanwell and some fun making it fit. I already ordered the meanwell ;)
Please don't "dump" the real one [-o<

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IanJeffray
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Re: A4000 PSU go pop

Post by IanJeffray »

daveejhitchins wrote:
Thu Sep 23, 2021 12:24 pm
Please don't "dump" the real one [-o<
Well the PCB is free to anyone who'd like it... but I don't think it's much use. THe new board will have to be wedged in the existing PSU enclosure, for its rear sockets at least -- I'm hopeful it'll be impossible to tell there's a replacement in there once I'm done :)

Better than my current situation of hanging an old PC AT PSU out of the podule slot anyway :lol:
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IanJeffray
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Re: A4000 PSU go pop

Post by IanJeffray »

Meanwell supply arrived. I always forget how diddy these things are. Sat next to the original A4000 board for reference...
IMG_E7505.JPG
Fits in the case no worries at all of course. Should easily mount with new pillars through the base.
IMG_E7506.JPG
I expect the most annoying part will be connecting the ludicrously thick 14AWG original HD and motherboard cables to the output header.
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Re: A4000 PSU go pop

Post by philpem »

IanJeffray wrote:
Wed Sep 22, 2021 10:25 pm
But also...

IMG_7464.JPG

pretty sure that hole's not supposed to be there. Pull it. Reads 8 ohms. Not sure if that's as it should be or not.

Tempted to cut my losses and see if I can wedge another of those nice Meanwell boards in here. I don't like dealing with power electronics. :(
Based on the shape and the PCB markings, that's either a MOV (metal oxide varistor) being used as a surge suppressor, or a thermistor being used as an inrush limiter. Both are known to fail shorted on occasion.

If you're also getting 8 Ohms between live and neutral, it's an MOV. The power supply will work without it, but with reduced surge suppression capability.

They're replaceable and cheap - certainly one of the cheapest PSU repairs going. That said, a shiny new Meanwell will be far more efficient and probably more reliable in the long run!
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IanJeffray
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Re: A4000 PSU go pop : replacement fix

Post by IanJeffray »

Mounted the new board on one of the existing pillars, using the board itself as a template for positioning the holes on the underside of the PSU case, drilling through and adding new pillars. Gel superglue as threadlock on the nuts.
IMG_7526.jpg
The hardest part by far was sorting the cables in to the JST connectors. I soldered the switch cable directly to the input socket, but had to jam the loop-through connector in to the power-input socket on the board (output from the switch). Crimp ring connector for the GND cable.
IMG_7528.JPG
And then had to grapple with the fankly ridiculous 14AWG mainboard and drive cables, putting pairs in to crimps for all bar one of the 5v, and the -12v. Not easy at all - so stripped back the insulation much further than usual, then applied heatshrink round the combined wires. The wires are also horribly thick even to bend so quickly to escape the PSU box. Happy that these are properly socketed now, but I can see why the original board just used crude wires soldered direclty in to the board.
IMG_7527.JPG
All running just fine and nobody would have a clue unless you open the PSU cage. Sorted.
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Re: A4000 PSU go pop : replacement fix

Post by a1exh »

Looks very good. As always :-)
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