Need advice on how to best clean/de-rust an IBM 5051 w/o damaging it any further

ropersonline said:

Is there any other procedure I could follow in addition to waiting an hour? Is there any way to safely deliberately discharge the capacitors in the PSU?

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The use of an appropriately rated resistor (value and power), with insulated leads. There is a construction guide at [here] for something that is suitable for a PC power supply.

The amount of time required to apply the resistor will vary. It will depend on a few factors. To confirm that a capacitor is discharged, measure the voltage over it using a voltmeter.

This subject is covered on the Internet.

Thanks for the advice.

paul said:

The fan is not hard to replace and the Papst brand is top notch.

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I had never seen a metal and 220V PSU fan before. So you're saying this is not that obscure and hard to source after all? (Well, thankfully it still seems to run for now.)
Also, I believe I mentioned that the fan is riveted to the PSU case (though it may be that that message is still awaiting approval). Is there a special tool that can carefully punch the rivets out, and that would also allow you to re-rivet? Personally, I'm not used to dealing with rivets, and replacing anything riveted meets my definition of "hard". YMMV of course. ;-)

modem7 said:

The use of an appropriately rated resistor (value and power), with insulated leads. There is a construction guide at [here] for something that is suitable for a PC power supply.

The amount of time required to apply the resistor will vary. It will depend on a few factors. To confirm that a capacitor is discharged, measure the voltage over it using a voltmeter.

This subject is covered on the Internet.

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Thank you very much. That's very useful information – I didn't even know capacitor discharge tools existed, so I wouldn't even have known what to google. You've fixed that.

I've actually managed to zap myself on a microwave oven in the past. I've never personally hear a pig scream, but I imagine that must sound like I did. You've just helped me not to "cap my ass".

Btw., if you want to see just the opposite, if you want to see someone who does zap himself, with caps and just about anything else, may I recommend the very entertaining Mehdi Sadaghdar. Start at the bottom (now we here).

ropersonline said:

I've actually managed to zap myself on a microwave oven in the past. I've never personally hear a pig scream, but I imagine that must sound like I did. You've just helped me not to "cap my ass".

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A very real possibility of bodily harm! I managed to connect my lips with a large cap in a color TV circa 1973, and couldn't form understandable speech for 2 days!

NEVER stick your head into an old TV cabinet...
gwk

ropersonline said:

Is there a special tool that can carefully punch the rivets out, and that would also allow you to re-rivet? Personally, I'm not used to dealing with rivets, and replacing anything riveted meets my definition of "hard". YMMV of course. ;-)

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You can use a drill to carefully drill the heads off a rivet so they let go. As for replacing them, I'd figure out a way to use some screws and nuts to hold it on again.

GiGaBiTe said:

You can use a drill to carefully drill the heads off a rivet so they let go. As for replacing them, I'd figure out a way to use some screws and nuts to hold it on again.

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As GigaBite said, drill them out, and then replace them with PopRivets--the tool & rivets are cheap at HarbourFreight and they work very well!

gwk

ropersonline said:

I had never seen a metal and 220V PSU fan before. So you're saying this is not that obscure and hard to source after all? (Well, thankfully it still seems to run for now.)
Also, I believe I mentioned that the fan is riveted to the PSU case (though it may be that that message is still awaiting approval). Is there a special tool that can carefully punch the rivets out, and that would also allow you to re-rivet? Personally, I'm not used to dealing with rivets, and replacing anything riveted meets my definition of "hard". YMMV of course. ;-)

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No, metal AC "muffin" fans are not difficult to find. However, I find them fairly noisy when compared to brushless DC fans. Were this my system, I'd probably go for the DC fan--and there is a precedent. Later 5150s shipped with DC fans.

I'm not sure why you keep bringing up WD-40...it's a light oil that's ok for temporary lubrication and short-term protection of clean bare metal from rusting. That's it. It's not a cleaner/rust remover/rust converter or anything like that.

If you want it perfect, take it to a body shop and have them media blast and paint it. That won't be cheap though.

However the rust really isn't that bad, even on the cover. I bet you could remove it easily with electrolysis.

WD-40 = mostly Stoddard solvent--the "WD" refers to the property as a "water displacer".

This afternoon, I was prodded into washing my truck--I usually do it with a bucket of sudsy water and a soft brush on a long handle. I noticed a few spots of rust bubbling up through the paint on the metal handle and decided to see how far the rust had progressed. Off to the shop to a buffer with a wire wheel. Although on a few spots of rust had managed to bubble up through the painted handle, the wire wheel showed that well over half the surface under the paint had rusted. I finished the job with a flap wheel and a new coat of primer and paint and the thing was good again.

The point of this is to provide more confirmation that when you see a few small spots of rust showing through paint that the problem is usually much more pervasive. I prefer blasting with walnut hulls as they're chemically non-reactive, but others have mentioned soda. Take your pick.

The active ingredient in WD-40 is oil. That's what will be left behind.

While it's true that paint hides rust, his computer case hasn't been sitting outside in the rain for a decade nor has it been driven on salty roads. He's not going to have anything more than minor pitting after cleaning it up.

Plasma said:

The active ingredient in WD-40 is oil. That's what will be left behind.

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I agree 1000%!!!

*Please*
Anyone reading this thread--DO NOT USE WD-40 on Circuit Boards OR ANY CIRCUITRY--It will coat everything WITH OIL.

Just because the "D" in WD-40 means water displacement, does NOT mean it's good for electronics! The "displacement" in this case, is OIL for WATER...

gwk

The primary ingredient in WD-40 is (about half) is CAS 64742-47-8, which could be called "white kerosene", basically a fuel. A little less of the other half is a light petroleum oil, what's left usually includes a surfactant (detergent), which probably helps to break the surface tension of any water.

The point that I agree on is that WD40 isn't the right tool for the purpose. Computer gear sitting for years in a damp basement can be shot through with rust and not be obviously rusted. The best way to tell is to scrape the area with rust and see how far the stuff has propagated. The shot of the cover gives the impression that rust has become quite widespread.

Chuck(G) said:

Later 5150s shipped with DC fans.

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My later model 5150 240V 63W PSU's have AC fans, Papst type 8850N but in grey not black, Still nice and quiet after all these years, Can't say the same for my 5160 PSU fans though, A couple of them still have ETRI fans in ( noisy buggers ) and i replaced the fans in the machines i regularly use some years ago.

As I understand the noise problem (and I'm pretty sensitive to noise, such that I used to take old PC-AT PSUs and drop the supply voltage to the DC fans), AC fans have a larger "core" containing the motor, limiting the area available for the fan blades themselves, so a noisier design has to be employed. True or not, the several AC fans that I have all have a characteristic "whine" to them. They vary from the Papst units, to traditional Rotron units and a couple of Japanese (probably Panaflo, but I don't recall) models.

I think that the move to DC fans was driven by the use of multi-supply AC voltage SMPSUs. You could sell the unit for both 120/240V 50-60Hz.

I find the fan noise from my modern desktop moderately annoying, even though it's much quieter than the PC and XT-style machines.

I hate noise as much as i do rust in a computer, Rusty cases go in the bin, My main XT 5160 is the quietest PC i have since i replaced the psu fan with a 12V DC fan some years ago and use CF as a hard drive.

Not as quiet as my Neoware thin clients, I'll wager

I've been following this thread hoping to see some solid resolution of something that a common collector can do with rusty cases, but so far it has been all over the place.

So, yes, the ideal solution is to take it to a professional, and have them blast/repowder it. Perhaps a few people here have that kind of equipment, know other that do it, or have piles of money, but not most.

So what exactly should a common person do within reason? (things one can get at Home Repo, etc)

I would hope that some commonly available rust remover, plus some kind of spray paint would be a serviceable solution? At least one that would improve the appearance, and halt rust? Would any of this prevent a professional form re-doing it later?

Well, over and over, you'll see the term "surface preparation". You can rechanically remove rusted areas or try a rust converter--but don't expect a nice-looking finish with the latter. Really, for a nice-looking job, there are no shortcuts. Remove or treat the rust, use a good primer and finish coat.

At least that's the way I see it. If you discover a shortcut, let us know about it.

Hello and welcome back, fellow vintage computerists! ;-)

First, thanks again for all your help so far. Now, to business:

It is getting "exciting" over here, because I was emboldened enough to finally return to the electronics part, having put the nuts and bolts, and dust and grime part on the back burner, after what felt like sufficient de-dusting and surface cleaning to try for "proof of life". (I'll return to the de-rusting later. If what follows should properly go into a new thread, please tell me.)

So yeah, I tried a full-on power-up test yesterday.

It did not go well.
There was a spark, crack and smoke, which seemed to emerge from the relay (marked 2 in the above mainboard picture), which in fairness had still looked a bit on the corroded side before the test. Note to self: For fast unplugging, NEMA/Schuko may actually be preferable to BS 1363, which otherwise is of course superior in damn near every way.

So, with the relay firmly in my cross-hairs, I took out my magnifying glass and found that there seemed to be quite a bit of copper "rust" (technically copper corrosion or patina, I guess) inside the thing, and maybe even some residue. That's when I remembered that I'd had a MAJOR accident with a sugary fizzy drink bottle in the same room over a year ago. Could some of that stuff have gotten inside the case and inside the actual relay? I hope not, but it looked and seemed possible. I took the following pictures:


(Yes, I've taken the cover off there.)

This is what it says on the relay:
Omron – manufacturer
RU – UL-recognized component mark
0193D3 (on the side) – probably a serial# (no relevant search engine hits)
and finally:
G2V-UA-006000 – this seems to be the actual designation of the component.

On the board, what seems to be a "K1" is partially visible. K designates relays on PCBs, so that makes sense.

I searched for a replacement, but I can't seem to find anybody selling G2V-UA-006000 relays. They're probably long obsolete.

So I pondered my options.

But then–

...I suddenly discovered this:



Turns out the earlier stage appearance of Messrs. Snap, Crackle, and Pop had less to do with the DIPshit^W, sorry, DIP relay, and much more with a capricious tantalum capacitor throwing a critical terminal crisis tantrum and cracking its top.

The gentle reader is here kindly reminded of these wise words:
Indeed.
Indubitably.
Elementary, my dear Watson:

It appears that whatever happened to the Omron relay, —sugary pop or no sugary pop—, it certainly somehow ended up with enough internal corrosion to generate just the kind of undesired arcing fit to cause another kind of pop; to wit: dispatch the primus inter pares of the tantalum infantry to Valhalla, Wagner-style.
(Or maybe Tchaikovsky-style. Pick your preference.)

I googled and "farnelled" and "mousered" 10-16 capacitors, and the component I killed seems to be a "tantalum capacitor, solid leaded, 10-16V, triple lead". That would mean it's 10µF, 16 Volt. However, on page D-21 of the IBM Technical Reference for the 5150, =one of the logic diagrams for the 64-256K mainboard, it says: "All caps are 8.2µF tantalum on this page", and many of the caps on that page are labelled "C7" in the diagram – the same designation as the one next to the "10-16 ➁"-labelled capacitors on my actual board. (There are several C7 caps on the board.)
Does the difference between 8.2µF and 10µF not matter? Am I correct in inferring that "10-16 ➁" means a 10µF 16V tantalum capacitor, or have I made a mistake? Anybody know what the "➁" stands for?

I have actually already ordered some 10µF 25V triple lead tantalum caps to replace the one I killed, but I would be loathe to **** up even harder, so that's why I'm still asking you lot, to make sure I spike lee. Not that I'm categorically opposed to the idea of ****ing up, but let's face it, the Mogherinis and Mayers of this world are probably not too interested in nannying washouts like yours truly.

I then discovered I actually had a 10µF 25V capacitor floating around:



...but it's an electrolytic one, and the Interwebs tell me that replacing tantalum caps with elcos, even just for testing, is apparently a major no-no, because of parasitic effects. Or so I read.

Returning to the relay which probably also needs fixing, I further studied the IBM TechRef, and was able to identify Rusty the Relay in there:



I have cleaned the relay as best I could without using any water/solvent. The green stuff is pretty much all gone. The way I see it, I have the following options:

1. Trust that the "dry cleaning" of the relay is "good enough" to prevent further arcing, replace the blown C7 with the elco I've got here despite the warnings in the hope that it'll be good enough for a single proof of life test and try again. (This is probably a bad idea – or is it? Could I do further damage? Presumably the polarity matters too? How would I install the two-lead elco in there?)
2. Again, trust the "dry cleaning", wait for the tantalum 10µF 25V caps to arrive, replace the blows C7 with one of them and try again.
3. Use water/distilled water to wet-clean/water wash the relay or the entire board and let it dry for a few days, install a replacement C7, and try again. (Is there another solvent I should/could preferably try?)
4. Unsolder the relay for separate, immersive cleaning, and act as above. Can I easily go wrong with the soldering there? I know some more modern PCBs have not just two layers with traces on both sides of the board, but may actually be multilayer, potentially complicating the way components are connected. Am I right in thinking that the 5150 board is simply double-sided, with unproblematic all-the-way-through THT vias?
5. Find an original or compatible replacement for the G2V-UA-006000 – unsolder and replace. Is anyone able to help with that? Can anyone tell from the logic diagram exactly what kind of DIP relay I should order? Or does anyone know where to get the original? I can't even find a spec sheet for the G2V-UA-006000. The only places I could "find" G2V-UA-006000 relays online were SEO-spamming "vendors" trolling for business and requiring a 500 parts minimum order. Translation: These guys don't stock the G2V-UA-006000, but if someone were to actually order from them, they'd try to get someone in Shenzhen to fab the order; or they'll talk you into buying something else, either of which may or may not work in the 5150.
6. Lose faith in this board and order a replacement. $$$
7. Abandon ship and actually order a second 5150 CPU, which might even have a non-rusty case. Despite the work-reducing advantages, the wastefulness makes this my least preferred option. Also, $$$$$. Or £££££ or €€€€€, whichever the case may be, but definitely not ¢¢.

If anyone has any useful input/advice on what to do, what not to do, any help would be very gratefully appreciated.

SomeGuy said:

I would hope that some commonly available rust remover, plus some kind of spray paint would be a serviceable solution? At least one that would improve the appearance, and halt rust? Would any of this prevent a professional form re-doing it later?

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You can use electrolysis to remove rust:

https://www.youtube.com/watch?v=AQNvhUYqCkw

I've done this for various rusty car parts and it works fine, though I used baking soda instead of washing soda. You'll need a tub large enough to contain your part and several sacrificial iron electrodes, threaded rods work well.

Just be aware that after you treat the part and remove it from the electrolysis tank, it will get more surface rust VERY quick unless you put a coating of oil on it, or paint. So have your whole assembly process setup beforehand.