Old Compaq Armada internal PSU repair

[stj]

Re: Old Compaq Armada internal PSU repair

the 33uf startup cap has bad internal leakage between the contacts.
the higher uf reading is the givaway.

the psu will be good-as-new if the caps are good.
psu's dont age, just the caps because they are liquid-filled.

on that subject, at some point you should inspect the laptop board and the backlight invertor circuit for leaking caps

[momaka]

Re: Old Compaq Armada internal PSU repair

BTW, for the startup cap, I'm thinking getting these. They should be good right? They are Panasonic FR's

Looks good to me.

For the output caps, I can't seem to find any readily available replacements at that exact spec. Hmmm... I have one of those M-Testers. Should I pull them out and measure their ESR and capacitance? Is that a good enough test?

Usually yes.

for the startup i would raise it to 47uf
longer life and cheaper and more common than 33uf.

I wouldn't.

Sure going from 33 uF to 47 uF is likely not going to cause issues... but I found in a few cases, it does mess with the short-circuit / OL protection time, so I choose not to mess with these unless I really don't have any proper replacements available.

In regards to the 47 uF lasting longer than the 33 uF... not really. If they are both 5x11 mm case size, it won't make any significant difference even 10-15 years down the road.

So stick with what the manufacturer used. The price difference between 33 uF and 47 uF is almost non-existent, even when buying huge quantities like manufacturers do. So I doubt they went with 33 uF to save on costs.

you cant use regular barrel plugs from stuff like radio's because they can only handle one or two amps

Depends on their size and how well they are made.
I'd trust an old scavenged barrel plug from a router (or similar) more than a "100% brand new and high quality" junk from China.

But is that REALLY a good idea? Is it really safe to use a 20+ year old PSU, even if I re-cap it and it outputs a stable 18v? I'm nervous it'll fail in a different way and kill my laptop...

Well, it's a relatively safe alternative.
After all, the original PSU came with Nichicon capacitors and not some ultra-cheap low-end junk. Granted back in those days, many PSUs still used good caps, even from lower-tier manufacturers (though not always, of course.) So there's a really good chance this is a well-designed PSU and won't kill anything if it goes bad. Judging by the one picture you posted, it seems to be constructed pretty well. At least I would trust it way more than any new cheap "Replace" adapter from China with junk caps, questionable semiconductors, and who knows what other cut corners.

Of course, if you don't want to fiddle with the old PSU, then using a genuine name-brand OEM adapter (like from Dell, HP, Lenovo, and etc.) would be the safest and easiest route.

Ohhhh, I pulled out the startup cap and measured its ESR.
https://cdn.discordapp.com/attachmen...127_185357.jpg

Isn't that super high?

Capacitance is still in spec, though getting close to the upper end of +20%, suggesting high-ish internal leakage.
ESR is not high for such old general purpose series cap. In fact, KME series production was discontinued a very long time ago (early-mid 90's, IIRC) and was replaced by KMG. So at such an old age, it just doesn't hurt to replace it anyways. The Panny FR cap will have a fraction of that ESR.

The output cap, in contrast, seems fine
https://cdn.discordapp.com/attachmen...127_184723.jpg

Are the output caps rated at 680 uF? If so, the capacitance is still in spec... though getting a little low (but that's normal, given their age.)
On the other hand, if the output caps are 470 uF, they are definitely reading too high and need to be replaced. If they are 560 uF caps (weird cap size, yes), then they are bang-on.
ESR seems a little high-ish too, but probably OK for their age. I don't think the PSU is not starting because of them.
These being Nichicon PL series, the main thing to check is for any green corrosion on their leads on the bottom, right near the rubber plug. If you see any, replace them and don't re-use them. If not, they might be OK to put back, at least for now to see if the PSU starts up with the new startup cap.
If the PSU doesn't start up, check the usual stuff: output rectifying diode for short-circuit, primary-side auxiliary winding rectifying diode, and finally the 431 shunt on the secondary and opto-coupler.

BTW, since the PSU is not powering ON, MAKE SURE TO DISCHARGE THE PRIMARY CAPACITOR(S) BEFORE starting work on the PSU. With faults like this, sometimes the primary caps can remain charged for a long time with over 300V DC. It won't kill you, but can hurt and definitely scare you. So just beware and check the primary cap(s)'s voltage before doing any work. If they are charged, discharge them with something like a plug-in soldering iron or glue gun (connect the plug across the cap terminals - this will discharge the cap in a matter of a second or less.)

Yikes! What the hell? I commend you, I can't handle roaches. I'd throw up as soon as I pulled the outlet.

I can handle them, as in literally I don't mind picking them up with my hand... but otherwise to "handle them" in my home - NOPE.
I've been collecting & fixing junk discarded and used electronics for over 10 years now. I do absolutely everything I can to make sure my house does not get infested. Some of the things I picked up did have a few dead ones... and recently a microwave that had hatched eggs (but the egg shells were crumbly and old, so I lucked out.) Of course, anything I pick up or buy goes outside for a thorough inspection first. One thing I've learned from this "trade" (refurbishing and fixing old electronics) is that roaches have a very particular smell. I also tend to prefer to pickup things only in the winter when its really cold (below freezing) or summer (really hot.) In case of the former, the roaches will try to run away to a warmer place when the temperatures drop. So if I pickup a TV or something similar and leave it outside in the cold for a few days, chances are the roaches will run away to somewhere else to avoid the cold (their eggs can still be a problem, though, which is why I try to inspect every nook and cranny on everything I bring in... and it really sucks doing that in the freezing cold, but I just DO IT. ) In contrast, when it's hot in the summer, my hands are not freezing so I can take my time to open and inspect any item I pickup for as long as I like. And with the day being long, I don't have to worry about it getting too dark too early. So summer and winter are the seasons where I don't mind picking up stuff more often.
Also, both roaches and bed bugs cannot stand temperatures above 50C. So one easy trick to get rid of them is to build a big box and put a heater inside, then run it till everything reaches a nice toasty 50-55C. This will kill both the roaches and their eggs. No toxic chemicals or sprays needed.

[yuuki47]

Re: Old Compaq Armada internal PSU repair

If they are 560 uF caps (weird cap size, yes)

They are 560uf, and it's a weird size, so I can't find replacements. Can I use a higher capacitance or will that cause bad things to happen? My guess is that it won't, since they are just the output caps. But I'm not an expert, just a hobbyist.

BTW, since the PSU is not powering ON, MAKE SURE TO DISCHARGE THE PRIMARY CAPACITOR(S) BEFORE starting work on the PSU

Dont worry I am aware of things like these. I may not be knowledgeable but I know electronic safety pretty well, and why AC is a no-no.

I got shocked as a kid by a sketchy appliance and I jumped so high I reached the ceiling. The switching voltage contracted my muscles so bad they acted like springs

On that regard, the PSU is turning on, its just that it outputs 1.2v instead of 18v. But maybe that's considered "not turning on".

BTW, the startup cap has like plastic protective sleeves on the legs probably for insulation. Should I re-use those? I can slide them off...

[stj]

Re: Old Compaq Armada internal PSU repair

you mean it's raised from the board? are the holes the same spacing as the cap wires?

[yuuki47]

Re: Old Compaq Armada internal PSU repair

you mean it's raised from the board? are the holes the same spacing as the cap wires?

Yes they are the same space and straight. There's also a lot of glue there.

But whether it was raised from the board I don't know. It was too cramped and dark in there to know. Here's a photo:

[yuuki47]

Re: Old Compaq Armada internal PSU repair

Here's also the PSU where the cap was (you can see the pads)



These are all high-res images if you want to zoom

I wish I could get closer but my camera is not very good. As soon as I get too close, it can't focus.

[stj]

Re: Old Compaq Armada internal PSU repair

i wonder if it's so they can lean it away from that vertical board?
it clearly overlaps the space marked for the cap

[momaka]

Re: Old Compaq Armada internal PSU repair

They are 560uf, and it's a weird size, so I can't find replacements. Can I use a higher capacitance or will that cause bad things to happen? My guess is that it won't, since they are just the output caps. But I'm not an expert, just a hobbyist.

Yeah, 680 uF should be fine if you could get those to fit.

But don't go ordering new caps for these just quite yet, unless that somehow saves you on shipping costs. Reason I say this is because they are likely not the issue. Usually bad caps on the output will only cause the voltage to be slightly lower and not really become unstable until a load is put on there. So I think it's either the startup cap or something else.

Actually, while waiting for the replacement startup cap, you could re-install back the caps and heat the adapter with a hair dryer until it's somewhere around 45-50C. Then plug it in and see if the voltage comes up. The heat will cause the ESR of the caps to drop, so that's one easy way to test if the issue is with the capacitors or not (though this trick tends to work only if the caps are not too badly failed... which in your case, they aren't.)

Dont worry I am aware of things like these. I may not be knowledgeable but I know electronic safety pretty well, and why AC is a no-no.

AC is actually your friend - especially very high frequency stuff, because the higher the frequency, the less current that would try to pass through your body and the more it will try to pass through the outermost layer of your body/skin (making it less likely to pass high current through the heart.) On the other hand, AC will conduct through your skin at a much lower voltage compared to DC.

On that regard, the PSU is turning on, its just that it outputs 1.2v instead of 18v. But maybe that's considered "not turning on".

Well, it's neither and both in a way.

BTW, the startup cap has like plastic protective sleeves on the legs probably for insulation. Should I re-use those? I can slide them off...

Wouldn't hurt to.
I think they were installed due to the proximity of this cap to the leads of the big cap next to it. And probably also to raise the cap a little away from the board so that it doesn't run as hot.
The glue on the PCB looks like something Astec would use. Same in regards to the output capacitor choices (Nichicon PL). It might actually be an Astec-made PSU... and Astec is pretty good quality (and a big PSU OEM back then.)

[yuuki47]

Re: Old Compaq Armada internal PSU repair

Yeah, 680 uF should be fine if you could get those to fit.

But don't go ordering new caps for these just quite yet, unless that somehow saves you on shipping costs.

OK. Got it! I'll order the cap for now and replace it to see if it runs. Until then, I'll focus on other things. It should be here within 1-3 days.

The supply says "Nagano Japan Radio Company" on the back of PCB btw. The fact that its Japanese puts me a bit more at ease.

But all this cap talk makes me nervous. I have a Toshiba 310CDT that still works strongly even with the original hard drive (though it's been making a lot of parking noises lately) so maybe I should re-cap these before bad things happen.

The saddest part is that there also the tiny SMD caps. If one of those fails, it's not like its specs are printed on them, so there's no way to know what to replace them with unless you've got a schematic.

Sad to think that these laptops will die like that one day...

[yuuki47]

Re: Old Compaq Armada internal PSU repair

BTW I think someone asked a picture of the battery before? Here it is... it's a NiMh... although I don't think I'm comfortable with refitting new cells. Don't you need welding tools for that?




PS, sorry for not uploading image attachements. Won't do it again!

[stj]

Re: Old Compaq Armada internal PSU repair

no leaks - they may be good.
just need to charge and then flatten them a few times to condition the chemicals in them.

btw, surface-mount electrolytics do have the specs printed on them.

[yuuki47]

Re: Old Compaq Armada internal PSU repair

no leaks - they may be good.
just need to charge and then flatten them a few times to condition the chemicals in them.

btw, surface-mount electrolytics do have the specs printed on them.

You telling me that this 20 year old battery could work? Is it safe to just try it?

I'm guessing that soldering directly on top of battery cells is a horrible, horrible idea so if it works, it works. If it doesn't work, oh well, no battery. It's not a big deal to me. Though I'll still remove the cells to keep the container and charging controller, mostly because there'll be a big battery hole on the side of the laptop otherwise.

Also, I'm talking about the tiny SMD caps that are about the size of a rice grain. But maybe those don't fail as much.

[stj]

Re: Old Compaq Armada internal PSU repair

yes try it.
nimh batteries lose capacity slowly as they get used,
but unlike lithiums you cant really overcharge them or damage them by draining them too much

those tiny rectangular caps dont contain liquid - so no problem.

[Th3_uN1Qu3]

Re: Old Compaq Armada internal PSU repair

no leaks - they may be good.
just need to charge and then flatten them a few times to condition the chemicals in them.

btw, surface-mount electrolytics do have the specs printed on them.

You telling me that this 20 year old battery could work? Is it safe to just try it?

I'm guessing that soldering directly on top of battery cells is a horrible, horrible idea so if it works, it works. If it doesn't work, oh well, no battery. It's not a big deal to me..

It is a horrible, horrible idea for lithium. You may be able to get away with just a tiny bit of lost capacitance on this old NiMH, even if you retrofit new cells.

But you need a BIG soldering iron - it needs to get so hot and transfer heat so fast that just 3-5 seconds on top of a cell should flow the solder completely, else you give it a few minutes break then try again, a file or some sandpaper, and RA flux (rosin active, requires cleaning after you finish the job with isopropyl alcohol or paint thinner or it'll slowly eat at whatever you put it on, or straight acid flux - not the usual RMA used for working on boards.

RA flux is usually what you would use on a 50+ year old radio or TV set for reconditioning. Those ancient solder joints will laugh at any Amtech professional BGA repair, even if they never even THOUGHT about lead-free soldering at that time, and it is most likely high grade eutectic 63/37 Sn/Pb. Same for soldering on batteries. Is it a bad idea, yes, there are much better ways, and a DIY spot welder can be made from your junk bin and needs all of four parts (the fourth is the on/off switch, you don't actually need one, you can unplug it from the mains after you are done working with it!). But is it doable? Certainly.

Will that ancient chemistry catch fire or explode in your face while you are soldering on it? Zero chance. It's safe. Worst you can do is some smoke and damaging the cells. Give it a shot.

yes try it.
nimh batteries lose capacity slowly as they get used

True, but you forgot to mention the incredibly fast self-discharge rate, can't use them in a clock or remote - they'll go flat in a couple weeks where a single use alkaline will work for 2 years - and their bad habit of becoming a solid, huge, beefy wire (yeah, a fancy way for me to say hard short circuit) if left for too long on zero volts.

But they usually don't bloat, blow up or catch fire (no, scratch that, they never do. maybe vent some hydrogen from the safety valve if you REALLY abuse them, and you won't be able to smell it and even have any idea it happened, unless you're close and hear the hiss of the escaping gas), unlike modern day lithium.

You are still going to find NiMh packs on brand new power packs for cordless tools to this day, although they are falling out of fashion, very slowly. The chemistry is old and disadvantages many, but they're reliable workhorses and you can put a series X cap for limiting the AC mains in and one single diode as the ONLY charging circuit... and it'll just charge. Every day. For years. Safely. It's the high self discharge (leakage, if you wish) they have which allows this.

[yuuki47]

Re: Old Compaq Armada internal PSU repair

Will that ancient chemistry catch fire or explode in your face while you are soldering on it? Zero chance. It's safe. Worst you can do is some smoke and damaging the cells. Give it a shot.

My top priority is completing the repair on the laptop and the PSU, I may do this afterwards.

I have TS80P soldering iron and also a junky £10 one that is actually kinda ok. Was using it for years before I got the TS80P.

Anyway, I'm not that bothered about the battery as long as the laptop works.

[Th3_uN1Qu3]

Re: Old Compaq Armada internal PSU repair

Should be enough iron if you use both of them at the same time and do all the prep beforehand - file it or sand it down to make it coarse and have the solder get something to grip on, gobs of slightly acidic flux, and definitely 63/37 SnPb or that hybrid bastard snpb alloy with bismuth which melts at 138C.

The Chinese sell it in all forms and it is cheap. I bought a tiny tub of solder paste, "Mechanic" brand, ages ago then forgot about it for years. When I gave it a whirl, it's an absolutely beautiful thing. Think Chipquik but doesn't melt at regular operational temperature of most electronics, therefore it can be a permanent solution, not just for removing large parts with small irons. Yeah, you can leave it there. It won't melt, flow elsewhere or cause cold joints, and it is just as elastic as our favorite SnPb and even easier to work with.

[sam_sam_sam]

Re: Old Compaq Armada internal PSU repair

I wonder if these are special nicad batteries and if there are 7 or 8 cells in it

[stj]

Re: Old Compaq Armada internal PSU repair

8 nimh cells - it's on the label.

strangly the capacity isnt

[yuuki47]

Re: Old Compaq Armada internal PSU repair

I wonder if these are special nicad batteries and if there are 7 or 8 cells in it

There are eight. There is a green nylon cover or whatever material that is that just makes them appear as if they are three long tubes. The voltage makes sense too. 8*1.2=9.6v, which matches what's on the label.

I think they're standard cells...

But I wonder if the controller disables itself once the batteries go below a certain voltage, like lithium controllers do. I heard NiMh don't suffer from this problem though, right?

[stj]

Re: Old Compaq Armada internal PSU repair

just try it.
btw, if you do replace the cells and they are regular size then eneloop style will stay charged for years.
ikea sells rebranded ones pretty cheap
spot welders are also cheap if you have a car battery spare.
this guy reviews them
https://www.youtube.com/c/Luca_Techy/videos