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Argghhhhhhh! IBM 5322 went Snap Crackle and Pop!

S

Shadow Lord

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And of course all the magic white smoke came out....


(BTW: if this is the wrong forum Mike please relocate as necessary)

Okay, so I got a System 23 (5322) for Father's day from a friend. He said he had it for a while and he could turn it on but never got any further then that. He dropped it off this morning, I plugged it in, and it booted right up. Unfortunately it had a few errors and would not boot to "PROC START". Luckily I had the HMS and I had found this thread with some Google fu earlier...

From what I could glean there was an ROS critical error (error 10) and there was a problem w/ the +24V on one of the drives (error 39). As I was preparing to delve deeper into the HMS I heard SNAP, CRACKLE, and POP followed by the magic white smoke being spewed all about! DOH!

As I made a mad dash for the power switch I noted that 1. the CRT was continuing to work without any problems and 2. the fans were running just fine. These observations plus the +24V error earlier is giving me hope that the problem is not with the main PSU but with one of the floppy drives.

So anyone have info on these drives (Chuck(G) - you apparently had a sun in with them previously :)?) and how to take them apart? Looking from the outside in I can not see any caps on the drives that would have caused the issue at hand but I don't have a very clear view either. Also anyone have manuals, programs, etc. for this beast?

Thanks.

p.s. If pictures will help please let me know. I will of course post the obligatory computer pr0n later. :)

p.s.s. Based on this picture the only capacitor seems to be the overly massive one in the back. Looking at mine they seem to be fine but I could be wrong....

IBM 51Td.jpg
 
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That capacitor is the motor run capacitor. It's an AC oil unit, which accounts for its size. They rarely go out--and if they do, it's pretty dramatic. If it went out, the spindle wouldn't turn--I assume that it does.

Use your nose! Localize the failure by sniffing. Sometimes we forget about all five senses. This could be nothing more than an electrolytic cap going south. Check for bulging cans.
 
Chuck(G) said:
That capacitor is the motor run capacitor. It's an AC oil unit, which accounts for its size. They rarely go out--and if they do, it's pretty dramatic. If it went out, the spindle wouldn't turn--I assume that it does.

Use your nose! Localize the failure by sniffing. Sometimes we forget about all five senses. This could be nothing more than an electrolytic cap going south. Check for bulging cans.
Click to expand...

I've been trying to use my nose but the smell is over whelming and the space are tight so it is not a 100% sure thing. I tried to pull out the PSU but it isn't coming easy... I may have to take the whole thing apart and disconnect wires to pull it out. The stench MAY be a bit stronger from the PSU then the drives.

As for the spindle the one drive I can easily access does not turn. I tried turning the big bronze disk by hand and its no go. I have not re-powered on with the cover off to see if anything spins.
 
Lots of white smoke + computer continues to run + stinks like hell = line filter caps. Sniff to confirm. (I know it's not always that, but for me it has been, more so with IBM equipment)
My RT did this to me while I was using it. Machine didn't even flinch, but my partner who was behind it at the time did.
 
I've had two firecracker explosions this week. A couple of tantalums on two different boards. Lots of sparks and noise with each one. In both cases I removed the failed caps (well their remains) and, when restarted, the boards continued to function normally.
 
Rule of thumb: Electrolytic caps in switching supplies will[/b[ go bad. Not "if" but "when". The high frequencies used in switchers virtually guarantee this. Replace with solid electrolyte caps if possible.
 
Okay, anyone have any manuals/info/etc. on this system and how to take it apart? The HMS is mostly concerned with running the diagnostics off of the floppy. I think I need to take it all apart and see if I can find the offending caps in the PSU.
 
Okay a couple of weeks have gone by and I have completely disassembled the machine. Don't let WikiP fool you. The PSU does not just slide out for easy servicing. I even have the cabinet in pieces right now (which provided a great opportunity to wash and paint the damn thing but that will be in the restoration post.). Going back to the PSU the smell is from the PSU. Hard to tell where though. None of the caps look blown as I had expected. I am thinking of recapping the two circuit boards. One will be real easy. The other one not so much. Anyone can recommend a good source for 105C solid electrolyte caps to replace these guys? Ideally I'd like to replace everything and see if I can get another 30+ years of use out of the machine. Am I correct in assuming aluminum caps would be solid electrolytic caps? And any particular brand I should be after? Panasonic still a good one? Thanks.

Here are some pics for those looking for computer pr0n. ;)

PSU 1.jpg

PSU 2.jpg

PSU 3.jpg
 
I'm certainly no expert on PSUs, having only repaired a few, but those paper caps look dodgy and in need of replacement. I'd say the one on the left is the magic smoke culprit.

PSU 1.jpg
 
SteveH said:
I'm certainly no expert on PSUs, having only repaired a few, but those paper caps look dodgy and in need of replacement. I'd say the one on the left is the magic smoke culprit.

View attachment 19326
Click to expand...


Well I am no expert in electronics but it hasn't stopped me yet. Thanks for the heads up. I didn't even consider those as capacitors - although the uF rating on them should have been a dead give away. So how would I find a replacement for the paper ones?
 
Replacements are surprisingly easy to find as they're used in lots of equipment. They also seem to be optional (but a good idea for surges etc).
I'd be 95% confident they caused the smoke, but I don't think they'd stop the PSU from operating.

http://nz.mouser.com/ProductDetail/...GAEpiMZZMukHu%2bjC5l7YRRWQ4n9sQIihq5LhhZtNNM=

Not sure what the one on the left was, but for the other two. Once one goes, the others usually follow, so best to do them all at once.
I spot a couple of 0.1uF ones in there too.
 
Well,

Looks like SteveH and SpidersWeb hit the nail on the head. If I understand correctly the capacitors that blew are the line filtering capacitors which would jive well with SpidersWeb's experience (puff of smoke but computer kept working). Here are the pics of the blown caps:

PSU 4.jpg

PSU 5.jpg

PSU 6.jpg


So what is the recommendation on replacing these caps? Is there better technology out for these now that would make them last longer? Also given that the other caps look good would the general wisdom be to replace them any how?
 
SpidersWeb said:
Replacements are surprisingly easy to find as they're used in lots of equipment. They also seem to be optional (but a good idea for surges etc).
I'd be 95% confident they caused the smoke, but I don't think they'd stop the PSU from operating.

http://nz.mouser.com/ProductDetail/...GAEpiMZZMukHu%2bjC5l7YRRWQ4n9sQIihq5LhhZtNNM=

Not sure what the one on the left was, but for the other two. Once one goes, the others usually follow, so best to do them all at once.
I spot a couple of 0.1uF ones in there too.
Click to expand...

Thanks for the info. The 0.1s are the one's that actually blew. My question on finding a replacement was more along the lines of how can I tell the voltage rating. Sorry if this sounds a bit dullard but on the radial caps I look for V, uF, and can diameter (for best physical fit) once those match I try to get the capacitor with the highest temp rating. So how do I figure out the right replacement for the paper ones?
 
For the voltage spec, I use the "X2" parts - ~300Vac. They're regularly stocked and support voltages higher than you'd expect to see on that part of the PSU.
 
SpidersWeb said:
For the voltage spec, I use the "X2" parts - ~300Vac. They're regularly stocked and support voltages higher than you'd expect to see on that part of the PSU.
Click to expand...

Thanks. One question - the circuit board with the blown caps on it has a sticker on the back that says 750V. That is not the voltage rating for the PSU is it? Seems way high for a computer back then.

So would this part be total over kill? In a good way...
 
I would check where the caps connect to. I just realized this system runs a CRT. So there might be parts of the circuit (not necessairly the power supply) that do go up towards that level.
From the CRTs I've been working on, I haven't seen those caps used for anything other than mains filtering, but it's worth checking. I'd expect it's more likely the circuit board itself is rated for up to 750V but worth checking.

If they're just on the mains input - you wouldn't expect to see more than 110 or 220Vac (if it has a voltage doubler). When you desolder what's in there now, you will be able to see their codes on the side of them (as a double check).

Is there a circuit diagram for this?
 
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Okay,

So I finally got a chance to pull the capacitors out of the PSU. I believe they are all class X caps made by RIFA which I guess became RIFA-EVOX which is now Kemet.

C1: 0.1uF, 250V, X
C2: 0.1uF, 250V, X
C3: 0.01uF, 250V,
C4: 0.01uF, 250V,
C27: 0.022uF, 250V, X1
C28: 0.022uF, 250V, X1

So how do I go about ordering replacements on these? I have to admit I am unfamiliar with these capacitors. For example there are two V ratings on the caps: 125 VAC and 250V. So does that mean 125V AC and 250V DC? Also, does the "higher temp tolerance" adage apply to these guys? Basically, since I am replacing them I see I have two choices: 1. Replace them with as close to the originals for authenticity or 2. replace them with something better for longer life. I like option 2 in this case myself ;).
 
Shadow Lord said:
So I finally got a chance to pull the capacitors out of the PSU. I believe they are all class X caps ...
Click to expand...
Per the image below, any ones that are grounded are usually Y types.

basic_ac_filter.jpg


The distinction between X and Y types is explained in the 'further reading' documents within the 'Line Suppression Capacitor' section at [here].
 
Shadow Lord said:
For example there are two V ratings on the caps: 125 VAC and 250V.
So does that mean 125V AC and 250V DC?
Click to expand...
If there is a ~ (tilde) symbol to the right of the 'V', then that means AC.

The capacitor pictured [here] has two AC voltage ratings. My reading of the specifications under the photo is that each voltage rating is applicable to different test standards, i.e. the designer of a piece of equipment knows what standards they need to adhere to (for equipment certification), and from that, the designer then knows which of the voltage figures is applicable to them.

Maybe that's the same reason that your capacitors have dual voltage ratings.
 
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