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View Full Version : Compaq Portable II blown caps, need help identifying components!



VERAULT
September 17th, 2017, 03:50 PM
So I recently picked up a compaq portable II. Its not in the best condition, and the last couple owners clearly didnt love this machine. After opening it to check for debris, I powered it on. Got a high pitched rythmic sound, must be a cap trying to charge. I removed all the cards and tried again, so now the system fan will pulse or vibrate but not spin. I decided to put the cards back in and try again. two tantalum caps and a resistor blew. One cap on the cga card, one cap on the system board and a resistor on the power supply. I can see what the value of the caps on the cga card and mobo are although Im better with electrolytic caps, I cant make out the value of these ceramics. See attached photos.
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cga card cap is 106 16K
motherboard cap is 10-.15 +m2
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The resistor in the ps is so burnt I can only tell the outer color bar is gold on one side orange on the other, (possibly red)40827

if it is orange on one side and gold on the other, there are two other nearby resistors with a 300ohm value, see photo40828

Anyway, I want to order some of these caps to replace them all, and its tough to tell what resistor I need. If anyone can lend a hand at helping me restore this old compaq 286 portable it would be greatly appreciated.

VERAULT
September 18th, 2017, 01:59 AM
these pics got shrunk way down, ill zoom in and repost.

VERAULT
September 18th, 2017, 07:53 AM
took some closer pics, the one that is orange with 10-.15 +m2 or 10-15 +m2 is hard to read because the wording is so faint, I played with the contract.40838
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Does anyone have one of these compaq Portable II's or have experience with one? your help would be extrememly appreciated.

Chuck(G)
September 18th, 2017, 08:37 AM
Both are tantalum caps. The one marked 106-16K is 10 uF at 16VDC; the 10-15 is pretty much the same--10 uF at 15VDC. When you replace them, be sure to observe polarity--otherwise, you'll make lots of noise... :) Voltage ratings of 15 volts or more will be suitable.

I can't help with the burned resistor. Often, you can get a rough idea of the value by measuring the burned one, if it hasn't been burned in two.

VERAULT
September 18th, 2017, 08:42 AM
Thanks Chuck(G), so in theory I should be able to use 10uf 16Vdc tantalum caps for both applications right? I found these here? http://www.ebay.com/itm/321760723164
Do you think they would be a match for both sets of caps?

Chuck(G)
September 18th, 2017, 09:00 AM
Yup, they should be fine. Note that on the CGA card, the highest voltage encountered is only 5V; on the motherboard 12V. So there's a safety margin. Physically, they're probably going to be a bit smaller (time marches on and things get smaller), but that shouldn't be of any concern in this case.

VERAULT
September 18th, 2017, 09:02 AM
Thats great thanks Chuck(G) I suppose the next step is to guess what resistor on the PSU burned since I cannot find a schematic

VERAULT
September 22nd, 2017, 01:21 PM
ok, I have most of the replacement components in , but I noticed I missed one style of cap. I think it says K1Z (might be K12) 473 see photo, what kind of cap is this?40905

VERAULT
September 22nd, 2017, 01:37 PM
Just an update on the status of the compaq portable II, I replaced some caps that chuck(G) identified 2 on the system board and one on the cga board, as well as a resistor on the psu ( So far I am using a 300 ohm resistor as thats what I guessed it was) and the unit now boots! No keyboard or drives yet, but I am getting video to the crt and output to a commodore monitor. You cant tell by the pic but there is alot of noise on the video out, I think it has to do with a bad cap mentioned in the last post.40908

Chuck(G)
September 22nd, 2017, 01:51 PM
The value is .047 uF--my guess is a polyester or ceramic deal. Small-value caps like this tend not to fail very often, so I wouldn't treat it as suspect unless you've got a good reason to.

VERAULT
September 22nd, 2017, 02:00 PM
its actually still functioning, the problem is one of those 10-.15 +m2 caps right next to it BURNED HOT AND BRIGHT, and charred it up pretty badly, and a large old school 80's resistor next to it is all blacked as well (although I think the resistor is fine) the cap I mentioned in the last post is actually charred and chipping away, it didnt do it on its own, it was burned by proxy.

VERAULT
September 22nd, 2017, 02:03 PM
by the way I am not finding any caps online with a .047 uf value, (i mostly deal with ebay or amazon, I only go to the big electronics distributors for switches or relays that are hard to find)

Chuck(G)
September 22nd, 2017, 05:27 PM
.047 uf = 47 nf = 47000 pf.

Try putting a zero in front of the value:

ebay search (https://www.ebay.com/sch/i.html?_odkw=capacitor+473&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xcapacitor +0.047+uf.TRS0&_nkw=capacitor+0.047+uf&_sacat=0)

Pick whatever looks right.

VERAULT
September 23rd, 2017, 06:01 AM
Thanks Chuck(G), I ended up buying these as they most closely matched the component. http://www.ebay.com/itm/100-x-0-047uF-50V-Ceramic-Disc-Capacitors-USA-SELLER-Free-Shipping/221213493702

VERAULT
September 27th, 2017, 08:26 AM
So I ran into some more problems, (and if anyone thinks I should repost this or move the post somewhere else please let me know) I had the CRT and video card working since I replaced those 10uF tantalum capacitors. I am still waiting on the .047 uf capacitors to be delivered. The video card worked for a few days and then it started doing something funny. The video would start to get staticy and snowy and there would be a high pitch increasing sound while the video just snows away to a blank screen, it happens about 30 seconds to 50 seconds after turning on the power. The funny thing also is the sound seems to be coming from the analog board attached to the CRT.

Just to determine whether or not the issue is the card or the CRT I took the video card from my compaq Portable I which I know works fine, I installed it into the same slot in my portable II and tried it out, the CRT and video are FINE! And they stay fine indefinitely, I swap the card for the existing one that came with the portable II and again the video fizzles out.

See the photos, So I am waiting on those .047 uf caps and I ordered a new 82 OHM resistor as well since that one got a bit charred too just in case, the only other thing I thought of was maybe the crystal oscillator is bad? Its a 18.981 mhz crystal, only one I could find online was a 19mhz crystal :http://www.ebay.com/itm/MG-KYOCERA-Oscillator-19MHz-KXO-01-19-0000M-DIP-14-Qty-4/160723587212

Any ideas?
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SomeGuy
September 27th, 2017, 09:02 AM
That could be a number of things on the video board. But since it starts out stable and gets worse, it may be thermal related. Perhaps spraying components with compressed air to cool them might reveal which one is bad. The fault could be in a chip or an electrolytic capacitor.

VERAULT
September 27th, 2017, 09:39 AM
good idea someguy, however there are no electrolytic caps.

Chuck(G)
September 27th, 2017, 09:47 AM
Got an oscilloscope? Monitoring the video signals might lend a clue.

VERAULT
September 27th, 2017, 10:03 AM
Chuck(g) I have access to one, but I only have the most basic understanding of it, I wouldnt even know where to look.

Chuck(G)
September 27th, 2017, 10:10 AM
Well, you might start by looking at the video output (not the sync signals) just to see what's happening with respect to levels.

https://learn.sparkfun.com/tutorials/how-to-use-an-oscilloscope

VERAULT
September 28th, 2017, 04:42 AM
Ok, Ill give it a go, Ill do the working unit first so I have a baseline to compare it to.