RISCPC Power Supply Refurbish - 4 Kits Available

[daveejhitchins]

The second RISCPC I sold (here) had its power supply go pop That was despite carrying out extensive soak testing (18 hours a day for a week).

So . . . I have two further supplies: One in my own RISCPC and one spare that's waiting for a replacement mains switch (it arrived from Russia last week ). This thread will document the refurbishment describing each stage.

The first stage is to strip down the supply and create a list of parts that need replacing. I have in mind all electrolytes, critical 'other' capacitors and all semiconductors which will include the optocoupler*.

* Optocouplers tend to fade away rather than just fail. They are banned from any critical telecommunications equipment for that very reason e.g. they can't meet 1000000 hours MTBF, even with derating!

I'll also provide kits of parts for anyone wanting to refurbish their own supply. Reply here if you're interested and I'll order parts accordingly.

Comments welcome, of course.

Dave H

[danielj]

Dave, quite possibly if you're getting the parts for the 103watt one?

d.

[daveejhitchins]

Dave, quite possibly if you're getting the parts for the 103watt one?

d.

Hmmm . . . How many versions are there? The four I've had dealings with have all been the 103W - I think - don't remember checking

Dave H

[danielj]

The standard was a lower wattage - P/N 0196,110/T - 70W, and the 103W was P/N 0197,010/T

d.

[sP1d3r]

Dave, quite possibly if you're getting the parts for the 103watt one?

d.

Hmmm . . . How many versions are there? The four I've had dealings with have all been the 103W - I think - don't remember checking

Dave H

There's a 79W as well as far as I know.
How would you check the varistors, my supply has them soldered to the PFC capacitors.
It only outputs 11.3V on the 12V rail with no load, I saw a 103W supply for sale last month that also had 11.3V on the 12V rail.

[Kazzie]

CJE lists 70W, 103W, and 150W models for sale.

[danielj]

CJE lists 70W, 103W, and 150W models for sale.

That 150W is a bodge-job.

d.

[anightin]

I'll also provide kits of parts for anyone wanting to refurbish their own supply. Reply here if you're interested and I'll order parts accordingly.

Dave H

That's great Dave, I'd be interested in a couple of 103W kits please

[anightin]

BTW, does anyone know if there are RiscPC electrolytic cap kits available for the Motherboard variants? Most of my machines are recapped now except the RISC PCs

[danielj]

BTW, does anyone know if there are RiscPC electrolytic cap kits available for the Motherboard variants? Most of my machines are recapped now except the RISC PCs

No, but doing a list of replacements is somewhere on my list of to-dos. Have you ever done the A3020?

[anightin]

BTW, does anyone know if there are RiscPC electrolytic cap kits available for the Motherboard variants? Most of my machines are recapped now except the RISC PCs

No, but doing a list of replacements is somewhere on my list of to-dos. Have you ever done the A3020?

Not yet, that's not included in my most-of but you're right, there are 6 surface mount caps that I'm aware of and probably more urgent than the RISC PC one perhaps. Fortunately mine all seem to be fine at the moment.

So, RISC PC and A3020.

[sP1d3r]

I'll also provide kits of parts for anyone wanting to refurbish their own supply. Reply here if you're interested and I'll order parts accordingly.

Dave H

I'd like a kit please, Dave.

I've got:
Radial:
50V 100uf
50V 47uf
25V 33uf
50V 22uf
50V 1uf

X2:
275V .1uf
can't remember the other one.

The PFC capacitors are 200V 330uf with Marcon TNR G271K varistors soldered across the output terminals, that I can recall.

[daveejhitchins]

I've got:
Radial:
50V 100uf
50V 47uf
25V 33uf
50V 22uf
50V 1uf

X2:
275V .1uf
can't remember the other one.

The PFC capacitors are 200V 330uf with Marcon TNR G271K varistors soldered across the output terminals, that I can recall.

Have you a different power supply to me? The one I have is this:

No X caps and no PFC caps!

I've got an almost complete list that I'll post in the morning. Most caps are up-close-and-personal so I've had to take care in choosing!

Dave H

[dangardner]

I opened up my other RISC PC PSU, which has the same P/N but a different revision, and it looks very different:

PSU 1 (currently not working, PC111 optocoupler seems dead, has transformer bolted to the lid):

PSU 2 (currently working but with a noisy fan, no transformer on lid):

[mark71]

I'll also provide kits of parts for anyone wanting to refurbish their own supply. Reply here if you're interested and I'll order parts accordingly.

Hi Dave

Sign me up for 4 kits.

This brings up an interesting thing, whilst having Youtube videos of retro computers playing whilst working.... the likes of 'yan beta' who is a commodore fan who is a proponent of recapping all electrolytics, and retromancave recapping the SMC electrolytics on 90's boards.

There isn't much video's out there about the Acorn kit, there seems to be a lot activity in Electron's on Ebay but not much internet chatter about having to recap them, BBC's suffer from the PSU blue smoke problem, but Electrons power supply seems not to be a point of failure, no recap kits for electrons other than Beeb/Masters.

Are there parts list's for all the Arch's out there for the normal Electrolytics' and SMC's?, and do we need to start re-capping these machines now for their future survival?.

Just some thoughts.

Mark

[egel]

The only thing I've ever replaced in a Risc-PC PSU is the Schottky Barrier Rectifier. I miss that on the list. That part is heavily under dimensioned, but possibly only in the 70W version.

[sP1d3r]

Have you a different power supply to me? The one I have is this:

No X caps and no PFC caps!

I've got an almost complete list that I'll post in the morning. Most caps are up-close-and-personal so I've had to take care in choosing!

Dave H

My psu is like dangardner's psu1, more like an Astec than a Phihong.

BTW, does anyone know if there are RiscPC electrolytic cap kits available for the Motherboard variants? Most of my machines are recapped now except the RISC PCs

No, but doing a list of replacements is somewhere on my list of to-dos. Have you ever done the A3020?

I've refurbished an A3020, mostly thru' hole with a few SMD.

[danielj]

Are there parts list's for all the Arch's out there for the normal Electrolytics' and SMC's?, and do we need to start re-capping these machines now for their future survival?.

There are a few machines that genuinely need their motherboards recapping - the leaky amiga A600s/A1200s, and ZX Spectrums as out-of-spec caps can fry the RAM. There are very few electrolytics on 8bit acorn machines and they're basically all involved in smoothing. If it's misbehaving and it's the fault of the capacitor, replace it. If it's not, leave alone. There's a bit of a myth in some communities that recapping will fix all manner of ills...

PSUs are a different kettle of fish, they run hot, things dry out and go out of spec, and X2 caps explode

I've seen very little evidence *yet* that the SMD electrolytics go in the arcs, however I think it's worth keeping an eye on and might be worth preemptively replacing (but this is just my observation/opinion). Batteries are the biggy for the arcs.

I think reason why I'm personally reluctant to start seeing the acorn gear going down the blind re-capping route is simply the amount of "re-crapping" that goes on in the Amiga circles by people with low skill and a poor soldering iron, and the misguided assumption that it's some sort of panacea

[danielj]

I've refurbished an A3020, mostly thru' hole with a few SMD.

Were any of the SMDs on their way out?

d.

[sP1d3r]

I've refurbished an A3020, mostly thru' hole with a few SMD.

Were any of the SMDs on their way out?

d.

They all disintegrated when I removed them.

[danielj]

They all disintegrated when I removed them.

Leaky?

[daveejhitchins]

Right . . . From looking at the above posts it seems that there are at least 4 revisions! Does anyone have a higher revision than 4?

Attached is a spreadsheet for revision 1. If you don't have this revision please don't order a kit . . . yet!

NEEDED! Anyone with a different revision could you please make a list of the capacitors and Semiconductors (see the note below). Then I'll be able to merge the spreadsheet and offer kits for the appropriate revision (see notes).

Note:
I've only listed parts that come under stress or that have a finite life e.g. the major semiconductors, optocoupler and electrolytic capacitors. I have included, in the parts list attached, the mains input DC filter capacitor as it sits right up against the bridge rectifier e.g. it probably gets warm!

One part I've not fond: EGP30D - However, looking at the Datasheet for the EGP20D I would guess that the EGP30D is a 3A part as the EGP20D is a 2A part. As this diode supplies the -12V rail specified at 250mA I feel the EGP20D would be an adequate replacement (?).

By the way, RS has the best 'search' engine bar none, so far! But it still takes an age to do this - like 9 hours plus up to now There are just too many specs to consider e.g. Ive limited the range of suppliers, maximum temperature and life of the the capacitors . . . I've still to triple check before ordering.

If you've indicated that you would like a kit - please check your revision number and confirm your request. Thanks.

Dave H

REV1 Power Supply 09-07-20.xlsx.zip

(12.07 KiB) Downloaded 25 times

P.S. I'll move on the the main board later . . .

[sP1d3r]

They all disintegrated when I removed them.

Leaky?

Dried out, more like.

One part I've not fond: EGP30D - However, looking at the Datasheet for the EGP20D I would guess that the EGP30D is a 3A part as the EGP20D is a 2A part. As this diode supplies the -12V rail specified at 250mA I feel the EGP20D would be an adequate replacement (?).

I got EGP30D ultrafast 3A diodes from UTSource.com last year, for a Mac Classic.
I don't know what their shipping is like at the moment, since the virus they'd only ship express.

[daveejhitchins]

I got EGP30D ultrafast 3A diodes from UTSource.com last year, for a Mac Classic.
I don't know what their shipping is like at the moment, since the virus they'd only ship express.

Hmmm! Interesting - haven't found anything, at the moment, through Google. One thing I'm trying to do is order from as few companies as possible to minimise the postage. So far postage is zero . . . it's the Yorkshire in me

Would you happen to have a data sheet?

Dave H

[danielj]

Have you a different power supply to me? The one I have is this:
IMG_0665.jpg
No X caps and no PFC caps!

I've got an almost complete list that I'll post in the morning. Most caps are up-close-and-personal so I've had to take care in choosing!

Dave H

Mine says "Issue 4" on the label. I'm going to have to go diving inside it, aren't I?

d.

[daveejhitchins]

Have you a different power supply to me? The one I have is this:
IMG_0665.jpg
No X caps and no PFC caps!

I've got an almost complete list that I'll post in the morning. Most caps are up-close-and-personal so I've had to take care in choosing!

Dave H

Mine says "Issue 4" on the label. I'm going to have to go diving inside it, aren't I?

At least you wont have to do what I did, in anticipation of new parts, and that's removing them all . . . And some of them were glued . . .

Dave H

[sP1d3r]

Hmmm! Interesting - haven't found anything, at the moment, through Google. One thing I'm trying to do is order from as few companies as possible to minimise the postage. So far postage is zero . . . it's the Yorkshire in me

Would you happen to have a data sheet?

Dave H

There's a link to a datasheet in this Farnell listing, :
https://uk.farnell.com/on-semiconductor ... dp/2824869

I'll buy some parts for my psu if you go to the trouble of ordering and packaging Risc PC psu components, otherwise I'll take it under advisement to find some replacement parts, so far the PSU has worked fine.

I'm trying to 'extract' the softload from the Risc OS 3i4 on my PC at the moment, I want a fresh install from the resources on the IDE drive.

[daveejhitchins]

Many thanks for the link to the data sheet . . .

Dave H

[anightin]

Here are my PSUs for identification purposes, but looks like we've had these on the thread already:

[philpem]

I'll also provide kits of parts for anyone wanting to refurbish their own supply. Reply here if you're interested and I'll order parts accordingly.

I'll take two -- my daily-driver RISC PC has the higher rated PSU in there (it came with a second-slice upgrade). I think the other is sporting a 70-mumble Watt single-slice PSU.

It'd be great if you could do a universal kit.