Where to start resurrecting a RiscPC 700

Arc/RPCs, peripherals, RISCOS operating system & ARM kit eg GP2x, BeagleBoard
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VectorEyes
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Where to start resurrecting a RiscPC 700

Post by VectorEyes » Tue Apr 17, 2018 11:02 pm

Hello all,

My very first post on StarDot!

Many years ago I had a RiscPC 700. I was happy with it for many years but it's spent the last 15 years or more in the attic. For ages I've been telling myself that I should try to get it working. Ideally I'd like to get to the point that I can run a modern version of RiscOS, and also perhaps mount virtual discs from USB storage and play around with all the programs I used to use 20 years ago.

If I can get it to at least boot, then I'm going to be asking a few questions about the best way to 'modernise' the beautiful old machine. But the first problem is that, of course, the battery is horribly corroded (see picture). I'm going to snip it away from the motherboard tomorrow, but I was wondering if anyone could advise me on what I should do after that. Given the machine's age, is there even any point in attempting to repair it myself? Is it likely to be corroded beyond repair? I could do with some advice on whether to 1. Repair myself, 2. Send somewhere to have it refurbished or 3. Give up and berate myself for not doing this sooner.
HorriblyCorrodedBattery3.jpg
If there's a chance I might be able to save it, are there any guides that go through exactly how to strip and clean a RiscPC? I've tried searching online but haven't had much luck finding step-by-step guides which haven't already disappeared from the web!

Thanks very much, and looking forward to joining the StarDot community!

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danielj
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Re: Where to start resurrecting a RiscPC 700

Post by danielj » Wed Apr 18, 2018 5:40 am

Yes. I've seen worse!
Get the battery off. Snip it off :) then take everything you can off the board and treat the area that has been leaked on with distilled vinegar, agitating with an old toothbrush. Wash it all off really well with water, and give it a good rinse with distilled water if you're in a hard water area, then leave it to dry in a warm place for a day or two. After that it's time to try and assess the damage - do you have a multimeter?

d.

(edit: I should add, going beyond 3.7 or 4.something on a RiscPC is probably not worth the hassle - 5 is best used on something like the Raspberry Pi, which is much much faster. The RiscPC stuff is great for running old stuff though!)

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daveejhitchins
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Re: Where to start resurrecting a RiscPC 700

Post by daveejhitchins » Wed Apr 18, 2018 7:29 am

Welcome to the Forum, VectorEyes . . . Enjoy . . .

Good luck with your restoration. It may take awhile but well worth the end result. Lots of options for Floppy and Hard Drive replacements.

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Where to start resurrecting a RiscPC 700

Post by bagpuss22 » Thu Apr 19, 2018 11:51 pm

The majority of that looks like dust!

Like danielj states its going to be worth cleaning the whole area and then you can see exactly what
you have to work with.

It will be worth it in the end and you get a great satisfaction when it does happen. :D

Russ

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Re: Where to start resurrecting a RiscPC 700

Post by VectorEyes » Fri Apr 20, 2018 11:16 am

Thanks everyone for the replies, really helpful. I was planning to snip out the battery but I've realised that it's surprisingly difficult to get to the small bits of wire between the battery and the motherboard what with all the other components in the way, so this weekend I'll be disassembling entirely, cleaning off the dust, removing the battery and generally seeing what state the whole machine is in. I've cautiously hopeful that if I give it a good spring-clean it might even boot, but time will tell...

I think it might be time to buy a multimeter, soldering iron, mini vacuum cleaner... :)

I'll probably be back here in a few days with more questions. Thanks again for the help so far!

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Re: Where to start resurrecting a RiscPC 700

Post by danielj » Fri Apr 20, 2018 11:30 am

Don't worry about the mini vacuum :D just wash it all off with water when you wash the vinegar off. Don't forget to remove all things that can be removed first (ie simms, ROMs etc)

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Re: Where to start resurrecting a RiscPC 700

Post by DutchAcorn » Sat Apr 21, 2018 8:00 am

Welcome VectorEyes, and good luck with cleaning the PCB! You may also need to replace some components. The CMOS chip is sensitive to the alkali attack of the battery but you can still get them. We have seen some other repairs on the forum, so share your findings and we can help you along.
Paul

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Re: Where to start resurrecting a RiscPC 700

Post by simoni » Sat Apr 21, 2018 8:12 am

I'd generally advise against using a vacuum cleaner on a PCB as it can generate static discharge which your RISC PC won't like much :)

Instead, get yourself an ESD-safe brush and give the PCB a good brushing with it and then follow the advice above about washing the board. For removing the battery gunk vinegar is a good choice (simply because the 'gunk' is alkaline, so the acidic vinegar neutralises it). However, use white vinegar (not the brown stuff) and dilute it 50-50 with water just to make sure it's not too acidic (it's better to scrub a little more than damage the board with acid as well as the alkaline battery gunk :) ).

If any connectors are particularly bad you can also use a fibreglass pen to get them shiny again - however, this is quite an abrasive procedure, so only do it if the toothbrush/vinegar trick doesn't work.

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Re: Where to start resurrecting a RiscPC 700

Post by 1024MAK » Sat Apr 21, 2018 2:16 pm

Sorry, I disagree with you Simon on the dilution of the white vinegar. It's better to use it as is. It will not damage any tracks or components any more than they already are, as it will only be on the board for a matter of minutes. It's very important that any remaining alkaline is dealt with, or it may continue to attack tracks and components for years to come.

Unlike the alkaline leakage from the cell (battery) which could have been eating away at the metals for many years.

Do however give the board a really good wash with tap water afterwards. Then if you live in a hard water area, a final wash with demineralised water.

Mark
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Re: Where to start resurrecting a RiscPC 700

Post by VectorEyes » Sun Apr 22, 2018 12:58 am

First update: This evening, with the help of this guide...

http://www.apdl.org.uk/riscworld/volume ... /index.htm

... and a few gulps of Glenmorangie, I stripped the machine down, snipped the battery off, and assessed the leakage damage. Unfortunately it doesn't look great. The battery has leaked all the way down the motherboard to the reset switch and most of the components are covered in alkaline gunk:
AreaOfDespair.jpg
It's really crusted around the components:
GunkNearResetSwitch.jpg
I'm still going to try to fix it, but I'm wary of doing further damage. So, should I just go ahead and get started with the vinegar and a toothbrush? I'm slightly worried that vigorous brushing with a toothbrush might damage the components or the tracks, but given damage already done I'm not sure what else I can do. Do I just slowly work my way around everywhere I can see the gunk, trying to work it off? Is there any way to get it out from under the chips and other surface-mounted things, short of physically desoldering them all and then re-attaching (which is well beyond my capabilities, I think!)

A few other thoughts:

- Such an elegant machine! Dissassenbly was really pretty easy.
- It was a real trip down memory lane. It's got an ARM Switcher, Cyrix DX2, StrongARM and ARM700, a TV tuner card (sadly now totally useless, of course!) and a CDROM drive. Many happy memories of using it.
- The StrongARM daughterboard wobbles worryingly in its socket. I recall it doing the same thing 15 years ago and it not bothering me, but now it seems far too loose.
- Hardly any dust inside. I was pleasantly surprised.
- The 486DX card has lots of wires soldered onto it. It looks like a bit of a 'bodge job', although I wouldn't want to cast any aspersions on the manufacturers! I do recall that I could never get the StrongARM and 486 to work well together, the machine would always lock up after a few minutes. Hence the ARM Switcher, so I could use the ARM700 when I wanted to work on Windows.
- The motherboard was tiny compared to ones today!
- Really, really wish I'd removed the battery years ago!

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1024MAK
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Re: Where to start resurrecting a RiscPC 700

Post by 1024MAK » Sun Apr 22, 2018 10:35 am

It's not a good idea to try to desolder anything at this stage. The alkaline battery leakage affects the solder, making it very difficult to get it to heat up and flow.

So clean the affected areas as described above. Start by a wash with white vinegar only. Then take photos of the affected areas. Then use a toothbrush (a new one) with white vinegar. You may hear the sound of the white vinegar reacting. Don't worry, this is normal.

If any components come off the board, or any tracks or pads lift, don't panic. As the corrosion must have already have done too much damage already.

Once you have gone over an area, rinse with tap water. Then if needed, repeat the process again.

Note that solder will remain a dull grey and component leads/legs/tracks may come out as either copper colour, or may be green (verdigris) or brown (rust). The white vinegar and toothbrush may not remove this.

Only once this process has been done can the real extent of the damage be assessed.

Mark
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Re: Where to start resurrecting a RiscPC 700

Post by VectorEyes » Thu Apr 26, 2018 12:11 am

I've followed the excellent advice given so far, and managed to remove almost all of the gunk. It took me two nights, I realised that there was still quite a bit on some of the components after it had dried, so repeated the process.

There are two small cubic components near the reset switch that have a very small amount of the gunk at their base, but apart from that it seems to be gone, or at least it's gone from the visible areas (I can't speak for underneath the chips, etc!)

Would it be safe to try turning on the machine? Or is the advice generally to do as much as possible to assess damage, before turning it on?

(I'm going to leave the hard drive -- unused for over a decade -- unpowered for the moment. It would be nice to see whether there's a way to get the data off it, but before I turn see whether it's still alive, I think I should have a new HD ready to copy everything onto!)

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Re: Where to start resurrecting a RiscPC 700

Post by 1024MAK » Sat Apr 28, 2018 7:25 am

As long as the last operation was a good wash followed by plenty of time for all the moisture to evaporate (24 hours in a warm dry place with the PCB at a 33 to 45 degree angle or 48 hours if only in a place at normal room temperature). Then as long as you can't see any obvious damage during a visual inspection (short circuits, broken, damaged or missing components, or broken or missing PCB tracks), it is not likely to do any harm by powering on.

If operating out of the case, ensure it is on an insulated surface. The low voltage section is not dangerous, but be careful around the mains and power supply sections.

When powering up, don't lean over any part of the board, just in case a capacitor lets go with a bang. If you have a multimeter, see if you can clip it to any available +5V and 0V/GND connections, so you can monitor the voltage as you turn it on. It should come straight up to 5V (4.85V to 5.15V).

Good luck

Mark
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VectorEyes
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Re: Where to start resurrecting a RiscPC 700

Post by VectorEyes » Sun May 06, 2018 9:02 pm

This is taking me a while. It's proving very difficult to get the yellow stuff out from one particular section of the motherboard. I've now scrubbed it four times with vinegar, rinsed with water then de-ionised water, left to dry ... and each time I find a few more components with the gunk on them!

Is there any point in trying iso-propyl alcohol instead? I'm going to keep going with the vinegar a few more times but if people have had success with iso-propyl alcohol to get battery residue off I'd love to hear about it.

Meanwhile, in between scrub-then-dry runs, I thought it might be a good idea to take a look inside the power supply. Apparently it's meant to be easy to remove two screws on the side and fold it open, but I found that there was a component screwed onto the 'roof' of the PSU (with two screws that were hidden under one of the information stickers), and it was connected to the main board by wires so short that it was impossible to open it up. Then I stripped the heads off one of the top hidden screws trying to get the component off... :(

I managed to get a photo of the inside and it doesn't look good. I'm assuming that when things inside power supplies look like they've dried, shrunk and melted, it might be a good idea to replace them before trying to actually turn it on...?

This one is on the main board:
MeltedComponentOnMainBoard.jpg
And this is the one that's screwed to the roof of the PSU:
StuckToTheRoof.jpg
I'm just curious whether there's any chance this damage could be 'cosmetic' and the actual components are are fine, or whether the look of them suggests a problem I'll need to fix before I even get to testing the motherboard. If anyone's had to deal with similar situations I'd love to hear your advice!

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Re: Where to start resurrecting a RiscPC 700

Post by danielj » Sun May 06, 2018 9:19 pm

Isopropanol will take off grease, but it's not going to dissolve/neutralise anything that vinegar will, and it won't wash the salts away like water.
d.

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Re: Where to start resurrecting a RiscPC 700

Post by VectorEyes » Sun May 06, 2018 9:26 pm

Thanks Daniel, I suspected as much. Back to gentle scrubbing with vinegar then!

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Re: Where to start resurrecting a RiscPC 700

Post by 1024MAK » Sun May 06, 2018 9:47 pm

VectorEyes wrote:This is taking me a while. It's proving very difficult to get the yellow stuff out from one particular section of the motherboard. I've now scrubbed it four times with vinegar, rinsed with water then de-ionised water, left to dry ... and each time I find a few more components with the gunk on them!

Is there any point in trying iso-propyl alcohol instead? I'm going to keep going with the vinegar a few more times but if people have had success with iso-propyl alcohol to get battery residue off I'd love to hear about it.
The vinegar is used to neutralise the alkaline from the cell (battery) and for removing the "limescale" deposits. It is less useful for removing any resulting corrosion. IPA is next to useless for dealing with alkaline leakage, the "limescale" deposits or corrosion. Also, if the remaining deposits are now just cosmetic, don't worry too much about getting every little bit off.
VectorEyes wrote:I thought it might be a good idea to take a look inside the power supply.
VectorEyes wrote: This one is on the main board:
And this is the one that's screwed to the roof of the PSU:
The two components in your pictures are coils wound on formers. The coils are then wrapped in tape to hold them together and to give some limited protection. Sometimes magnetic components like this are dipped in a special varnish. So they can have a kinda melted look. But they both look normal to me. Also note that (outside CRT displays) transformers and similar inductors are one of the most reliable components there is.

Mark
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Re: Where to start resurrecting a RiscPC 700

Post by Bat » Sun May 06, 2018 10:39 pm

Hi,
Both transformers look fine to me, the smaller one you can see past the tape the copper wire looks great.
I don't see any cause for concern there :)
Cheers :)

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Re: Where to start resurrecting a RiscPC 700

Post by VectorEyes » Sun May 06, 2018 11:35 pm

Thanks guys, I really appreciate your replies. In that case I'll just get as much dust as possible out of the PSU and then put it back together again!

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Re: Where to start resurrecting a RiscPC 700

Post by 1024MAK » Mon May 07, 2018 8:32 am

Do have a good visual look at any/all the rectangular capacitors, look for any sign of stress or cracking of the cases.
And also have a good look at the cylindrical electrolytic capacitors, look for any distortion on the top. Is the top flat (good) or domed (bad). And look at the PCB end, is there any leakage or signs of corrosion. Any problems indicate the capacitor is failing.

Mark
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Re: Where to start resurrecting a RiscPC 700

Post by VectorEyes » Wed May 30, 2018 10:24 pm

After several weeks of being too busy, waiting for air-blower canisters to be delivered, cleaning all the dust out of the PSU, borrowing a multimeter to check the PSU voltages, etc, I finally got everything put back together, took a deep breath, turned it on...

... and was rewarded with the supervisor prompt!

Quick CMOS reset later, and I could even use the desktop. I apparently have a (reasonably, at least) functional RiscPC 700! Thanks so much to everyone for their help.

The next step is to get a new (removable this time!) CMOS battery... and then look into fitting an interface that'll allow me to use a CF/SD card as a hard drive. Then I'd like to see if I can resurrect the existing hard drives in the machine (one IDE, one SCSI) and get everything copied onto new 'less likely to expire at any moment' drives. But that's a matter for another thread, I think!

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