Repairing a dead A310 power supply

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Zarchos
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Re: Repairing a dead A310 power supply

Post by Zarchos » Sat Jan 24, 2015 10:28 pm

In this A310
http://www.ebay.fr/itm/Acorn-Archimedes ... SS:FR:3160
there's even a missing resistor.

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Re: Repairing a dead A310 power supply

Post by steve3000 » Sun Jan 25, 2015 9:04 am

Zarchos wrote:In this A310
http://www.ebay.fr/itm/Acorn-Archimedes ... SS:FR:3160
there's even a missing resistor.
Check the circuit diagram in that case. It could be another 'fix'...?

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paulv
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Re: Repairing a dead A310 power supply

Post by paulv » Sun Jan 25, 2015 10:27 am

It's quite possible. A lot of FCO's were meant to be applied to early Arc's. It's highly likely that the cut resistor which has just been repaired was one such FCO but I don't have the time to go through them all to check ATM.

Paul

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Re: Repairing a dead A310 power supply

Post by sirbod » Sun Jan 25, 2015 11:13 am

paulv wrote:A lot of FCO's were meant to be applied to early Arc's
Are the FCO's available online?

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Re: Repairing a dead A310 power supply

Post by paulv » Sun Jan 25, 2015 12:04 pm

Last edited by paulv on Sun Jan 25, 2015 12:59 pm, edited 1 time in total.

Zarchos
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Re: Repairing a dead A310 power supply

Post by Zarchos » Sun Jan 25, 2015 12:24 pm

Thanks for this gold mine of infos !

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paulv
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Re: Repairing a dead A310 power supply

Post by paulv » Sun Jan 25, 2015 1:08 pm

If the resistor you fixed was R39, then it should ideally be removed as part of FCO E009.

Paul

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Re: Repairing a dead A310 power supply

Post by Zarchos » Sun Jan 25, 2015 1:14 pm

paulv wrote:If the resistor you fixed was R39, then it should ideally be removed as part of FCO E009.

Paul
Thanks.
I understand why it had a leg in the air : it was on purpose.

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simonm
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Re: Repairing a dead A310 power supply

Post by simonm » Sat Sep 15, 2018 12:13 pm

Resurrecting this thread in the hope some kind folks could help out a non-hardware-techie type like me with fixing an old A310 I bought on gumtree. The seller wanted to show me it working, but when he did, a bunch of smoke came out of the machine so he offered it for just a tenner - bargain! :D

So, I'm ok with a soldering iron and a multi-meter, and keen to try my hand at getting it safely back up and running, but I've followed this thread and frankly I'm feeling a bit out of my depth as I dont have the electronics know-how really.

What kind of fault finding repair steps would you guys recommend I follow? I'm guessing the smoke is probably burnt out caps in the PSU similar to beebs? But what kind of caps? Where would I get them from? Are the caps mentioned here also a potential cause of the smoke?

I've hunted around for example process to follow, but this thread is the closest and most relevant one I found. However, some kind of checklist would be amazingly helpful if that's even possible?

Thanks so much!

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Re: Repairing a dead A310 power supply

Post by daveejhitchins » Sun Sep 16, 2018 8:02 am

I would think the first job would be to find out where the 'smoke' came from and work from there. Switch-Mode PSUs are no more difficult than any other type of circuit to repair - However, like all circuits, you need to understand how they work - with the added PSU caveat: Once the fault has been located - replace ANY component around it that may have been 'stressed' by the failure.

I'm sure there'll be lots of specific help on it's way - Main thing is not to be afraid of PSUs - But be carefull!

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Re: Repairing a dead A310 power supply

Post by 1024MAK » Sun Sep 16, 2018 8:18 am

Any electronic or electrical component that is overheating, being overloaded or self destructing can be the cause of smoke.

I recommend that you open it up and carry out a visual inspection by eye (under a good light) looking for any physical trace of the cause of the smoke, such as soot marks, blackened, damaged or distorted component(s).

Post a photo up of anything that looks suspicious.

If you don't know about being safe while working on power supply systems where DC voltages of up to 340V DC may be present (large electrolytic capacitors can hold a charge for many hours after the system is powered down) please ask for further advice.

Mark
Last edited by 1024MAK on Sun Sep 16, 2018 8:21 am, edited 1 time in total.

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simonm
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Re: Repairing a dead A310 power supply

Post by simonm » Sun Sep 16, 2018 11:08 am

Thanks, I think I'm going to journal what I do, in the event its helpful for future hardware beginners like me.
I recommend that you open it up and carry out a visual inspection by eye (under a good light) looking for any physical trace of the cause of the smoke, such as soot marks, blackened, damaged or distorted component(s).
I shall do this first then.
If you don't know about being safe while working on power supply systems where DC voltages of up to 340V DC may be present (large electrolytic capacitors can hold a charge for many hours after the system is powered down) please ask for further advice.
It's a new experience to me, but thanks for the tip - I'm aware of the safety in mind. Many years ago I worked in a TV repair shop where I acquired a healthy respect for electrical equipment! I spotted this link for safe cap discharge procedure.

Will post up as I progress - likely over a few weeks. Thanks for the guidance.

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Re: Repairing a dead A310 power supply

Post by RobC » Sun Sep 16, 2018 2:07 pm

I recently picked up some vintage graphics kit but the PSU in one of them was faulty and was causing the entire circuit to trip. I thought about repairing it but found a brand new Meanwell unit with better spec for less than £15. It was probably cheaper than replacing all the caps and certainly quicker than fault finding.

It might be worth looking into whether there's a suitable replacement for the Arc PSU. (It's a while since I've looked at an Arc PSU but when my R260's PSU died, I ended up using the innards from a spare RiscPC PSU.)

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Re: Repairing a dead A310 power supply

Post by simonm » Sat Sep 22, 2018 10:51 pm

Ok, so I had some time to disassemble a bit more of the beast.
The PSU in situ
2018-09-22 23.02.41.jpg
The ganky motherboard
2018-09-22 23.06.58.jpg
This was rattling around inside the PSU - looks like what's left of a capacitor
2018-09-22 23.17.18.jpg
The PSU - so my question is, how is this PCB disassembled/removed from the outer metal case? I've removed screws on top of case, and it does slide a bit down, but doesn't lift out easily and I didn't want to force it? I can't see any other way to get it out though...
2018-09-22 23.19.05.jpg
Last edited by simonm on Sun Sep 23, 2018 11:19 am, edited 1 time in total.

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danielj
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Re: Repairing a dead A310 power supply

Post by danielj » Sun Sep 23, 2018 5:19 am

More screws on top? Check under the label? I've not done one of these myself so I'm guessing. Also the plastic grommets in the side will i need to come out if there are any.

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Re: Repairing a dead A310 power supply

Post by zeem » Thu Sep 27, 2018 7:18 pm

It's probably recommended to replace them, but those particular capacitors are not required for the power supply to function. I've often removed them or left the blown remains in place and continued to use the machine in question.

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1024MAK
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Re: Repairing a dead A310 power supply

Post by 1024MAK » Thu Sep 27, 2018 8:48 pm

Image
Oh, what a surprise, it says RIFA on it :lol:

These being an interference suppression / filter paper insulation capacitor that is connected between line and neutral. The old ones do have a nasty habit of either going bang, or going up in smelly smoke (or both).

Mark

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Re: Repairing a dead A310 power supply

Post by simonm » Tue Nov 27, 2018 8:03 pm

Thanks for help so far.
Does anyone know how I get the black grommet loosened? I can't get the PCB out unless I can remove it.
IMG_20181127_200049.jpg

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simonm
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Re: Repairing a dead A310 power supply

Post by simonm » Tue Nov 27, 2018 8:25 pm

Ok. I decided to get gnarly with it. It pops out if you encourage it upwards with a screwdriver.
Right so now I can see the PCB. There are loads of caps! But which ones will be borked or nearly borked?
IMG_20181127_202012.jpg
IMG_20181127_202021.jpg
Here's the silver popped one
IMG_20181127_202107.jpg
Yep deffo explodinated

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Re: Repairing a dead A310 power supply

Post by simonm » Tue Nov 27, 2018 9:11 pm

Seems the caps on this board are very similar but not quite to the ones in Retroclinic's BBC cap repair kits.

C1 = X2 0.01uF (RC's are 10nF X2 RIFA)
C9 = 25V 470uF (RC's are 35V 220uF)
C2 = ??? (the popped one has burned so no idea what it is apart from some type of RIFA) (RC's are 100nF X2 RIFA)

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1024MAK
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Re: Repairing a dead A310 power supply

Post by 1024MAK » Tue Nov 27, 2018 9:39 pm

simonm wrote:
Tue Nov 27, 2018 8:03 pm
Thanks for help so far.
Does anyone know how I get the black grommet loosened? I can't get the PCB out unless I can remove it.
IMG_20181127_200049.jpg
Yeah, there is a special tool for it. I actually bought one. But can never find it when I want it!

Mark

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Re: Repairing a dead A310 power supply

Post by 1024MAK » Tue Nov 27, 2018 9:54 pm

simonm wrote:
Tue Nov 27, 2018 9:11 pm
Seems the caps on this board are very similar but not quite to the ones in Retroclinic's BBC cap repair kits.

C1 = X2 0.01uF (RC's are 10nF X2 RIFA)
C9 = 25V 470uF (RC's are 35V 220uF)
C2 = ??? (the popped one has burned so no idea what it is apart from some type of RIFA) (RC's are 100nF X2 RIFA)
For C1, 0.01uF is a 10nF. Both the same value, just using a different SI multiplier.
For C2, if it physically fits, a 100nF (or 0.1uF) type will be fine. They are interference suppression capacitors, so the value is not critical.
Both C1 and C2 must be X2 rated (for safety) as they are connected across a 230V AC mains supply.

On a BBC B PSU C9 is the “start-up” and “running” reservoir capacitor for the switching transistor. It is recommend to replace this for reliability rather than safety.

I don’t have a A310, so am not sure which one it will be on the A310 PSU. But it will be not too far from the metal cased transistor (mounted on the heatsink).

Mark
Last edited by 1024MAK on Tue Nov 27, 2018 10:44 pm, edited 1 time in total.

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Re: Repairing a dead A310 power supply

Post by IanS » Tue Nov 27, 2018 10:12 pm

simonm wrote:
Tue Nov 27, 2018 9:11 pm
Seems the caps on this board are very similar but not quite to the ones in Retroclinic's BBC cap repair kits.

C1 = X2 0.01uF (RC's are 10nF X2 RIFA)
C9 = 25V 470uF (RC's are 35V 220uF)
C2 = ??? (the popped one has burned so no idea what it is apart from some type of RIFA) (RC's are 100nF X2 RIFA)
I'd offer to look in my (unexploded) A310 PSU for the C2 value, but it looks suffiently different to yours, that it may not be helpful.
Attachments
PICT3616.JPG
A310 PSU (old pic)

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simonm
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Re: Repairing a dead A310 power supply

Post by simonm » Wed Nov 28, 2018 12:04 am

1024MAK wrote:
Tue Nov 27, 2018 9:54 pm

For C1, 0.01uF is a 10nF. Both the same value, just using a different SI multiplier.
For C2, if it physically fits, a 100nF (or 0.1uF) type will be fine. They are interference suppression capacitors, so the value is not critical.
Both C1 and C2 must be X2 rated (for safety) as they are connected across a 230V AC mains supply.

On a BBC B PSU C9 is the “start-up” and “running” reservoir capacitor for the switching transistor. It is recommend to replace this for reliability rather than safety.

I don’t have a A310, so am not sure which one it will be on the A310 PSU. But it will be not too far from the metal cased transistor (mounted on the heatsink).

Mark
Awesome thanks Mark. Of course - uF / nF ! Doh!

Pics of C9:
IMG_20181127_235953.jpg
C9 from side
IMG_20181128_000018.jpg
C9 from top

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simonm
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Re: Repairing a dead A310 power supply

Post by simonm » Wed Nov 28, 2018 12:06 am

IanS wrote:
Tue Nov 27, 2018 10:12 pm
I'd offer to look in my (unexploded) A310 PSU for the C2 value, but it looks suffiently different to yours, that it may not be helpful.
Thanks Ian. Crumbs, very different looking psu's! I wonder if my other A310 will be the same psu now!

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1024MAK
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Re: Repairing a dead A310 power supply

Post by 1024MAK » Wed Nov 28, 2018 10:15 am

That 470uF 25V capacitor does look like the “start-up” capacitor. Even if it is not, there is no harm in renewing it (it being close to a heatsink and therefore likely aging faster).

Replace it with a high quality 105oC 470uF 25V (or higher voltage) type.

Mark

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Re: Repairing a dead A310 power supply

Post by daveejhitchins » Wed Nov 28, 2018 10:22 am

Back to the original question of Black plastic grommet - a pair of pliers will do the job. Not as good a the correct tool, but hey! How many times will you want to use it?

Dave H :D
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