Compaq LTE/286 - capacitor plague?

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Compaq LTE/286 - capacitor plague?

Postby 133MHz » 2014-2-23 @ 04:03

Today at the usual flea market I picked up a Compaq LTE/286 laptop, no accessories, but for a mere $2 I couldn't say no! :lol: Aside from being dirty and missing the side covers it seems to be in good cosmetic condition.

I couldn't find the AC adapter specs (voltage/current/pinout) but I found out that the battery input takes 4.8V @ 5A, so I hooked it up to the +5V rail of an AT PSU to test it out. The hard drive spins up, but the power LED lights up for a split second and the computer itself stays dead. I unplugged the hard drive and the computer sprung back to life, but with the following symptoms:
  • No backlight.
  • Audible DC-DC SMPS squealing, varying in pitch with the display contrast setting.
  • BIOS throws up 601 Diskette controller error in conjunction with the usual dead CMOS battery issues.
  • Can't get it to boot off a floppy, no floppy access is being made by the system, and when a disk is inserted one of the motors runs continuously until said disk is ejected.

I had a closer look at the motherboard and noticed corrosion on the legs of almost every capacitor, suggesting electrolyte leakage a la Sega Game Gear (even the caps look physically similar to those of the GG). Does this mean that the Compaq LTE/286 suffers from capacitor plague like some Macintosh logic boards? I didn't find any mention of capacitor problems on these machines, and I find it hard to believe that mine is the only one like this.

Image

My plan is to recap the board with cheap 'lytics and hope that fixes the FDC issue. Since this is one of those Compaq machines where you need a setup disk to configure the CMOS, I guess that if the FDC is toast then the entire machine is done for. :depressed:
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Re: Compaq LTE/286 - capacitor plague?

Postby matze79 » 2016-2-06 @ 15:48

any progress ?
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Re: Compaq LTE/286 - capacitor plague?

Postby Logistics » 2016-2-06 @ 17:13

Oh, man! Even if you replace capacitors, you gotta get that junk off the motherboard--there is way too much oxidation and corrosion going on. I would be tempted to use some sort of agent to get rid of it.

The long, arduous way would probably be to use a white-vinegar and water mix, and a toothbrush to slowly get rid of it all. I would remove all the capacitors which you intend to replace, first. If the board was in MY possession, I would use ZEP Acidic Toilet Bowl Cleaner. I use it all over my house to get rid of the calcium build-up on the toilet, sinks, tub, faucets, etc. It also cleans up copper and brass in a hurry. I wouldn't leave it on for long as it probably wouldn't be good for something in the long-term, but the board needs to be washed, anyway so I would do a section, rinse, do another section, rinse, etc., then let the board dry out and recap it.
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Re: Compaq LTE/286 - capacitor plague?

Postby Asaki » 2016-2-07 @ 11:57

133MHz wrote:
  • Can't get it to boot off a floppy, no floppy access is being made by the system, and when a disk is inserted one of the motors runs continuously until said disk is ejected.


If it's anything like the LTE Elite, the belt inside has turned into dust. I have to put the HDD into a different laptop, or use my PCMCIA CF card adapter if I want to install anything.
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Re: Compaq LTE/286 - capacitor plague?

Postby 386_junkie » 2016-2-07 @ 14:07

Just replace the caps, and maybe give the board a clean... you'll find pretty much all functions will return back to normal. It is these caps that drive most (if not all) the system... if they leak, the system ain't getting the juice!
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Re: Compaq LTE/286 - capacitor plague?

Postby matze79 » 2016-2-07 @ 14:30

Asaki wrote:
133MHz wrote:
  • Can't get it to boot off a floppy, no floppy access is being made by the system, and when a disk is inserted one of the motors runs continuously until said disk is ejected.


If it's anything like the LTE Elite, the belt inside has turned into dust. I have to put the HDD into a different laptop, or use my PCMCIA CF card adapter if I want to install anything.


This damn Compaq needs to load its setup program from floppy to setup bios settings.. :O
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Re: Compaq LTE/286 - capacitor plague?

Postby 133MHz » 2016-2-08 @ 00:10

Wow, didn't realize this was almost two years ago! 8-O
From what I remember, when I began to clean up the board from the electrolyte residue several traces and vias started disintegrating due to the advanced corrosion, traces/vias so fine you'd need a single strand of fine copper to be able to repair them. I handed the board over to a friend who is more skilled than me at precision soldering, since it was only a favor it's probably still sitting on his 'pending' pile to this day.

I'm afraid it's probably too far gone at this point, if the corrosion managed to get into the intermediate layers through the vias and whatnot any efforts of cleaning, bridging and recapping might end up wasted.
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Re: Compaq LTE/286 - capacitor plague?

Postby matze79 » 2016-2-20 @ 14:54

The backlit on all units i have doesnt work.
I have 3 LTE's sitting here a LTE and 2x LTE/286

The floppy uses a belt, which needs to be replaced if it doesnt work anymore
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Re: Compaq LTE/286 - capacitor plague?

Postby matze79 » 2016-3-07 @ 17:41

Compaq LTE:
Image


Compaq 286LTE:
Image


Trying to Fix 286LTE:[img]
Image

Image
Soldered small wires on the tracks and run a wire from top to back (broken VIA).

i have now four of this compaq's.. 3 aluminium caps are leaking (always same 3) or burnt (short circuit)
leading into broken VIA's, broken pcb tracks

My boards are different from yours, i have less aluminium caps inside :O
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Re: Compaq LTE/286 - capacitor plague?

Postby matze79 » 2016-3-12 @ 17:15

Image

I got the Backlight working, unfortunally it don't won't boot from floppy, i already tried a different drive with new belt.
But no success, maybe the drivehead is bad.

All LTE's 8086 suffer from heavy capacitor leaking... i have two now. And both are really gone.
Even the Floppydrive has leaking Capacitors..
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Re: Compaq LTE/286 - capacitor plague?

Postby ultimate386 » 2016-3-12 @ 18:29

Wow, I had a LTE/286 about 10-15 years ago that had practically the exact same patch of dead pixels on the screen when I bought it on eBay. Fortunately I was able to find a NOS replacement screen on eBay as well! Alas, I ended up selling the system, carrying case and all, for all of $25 back on eBay when the power supply died :depressed: .
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Re: Compaq LTE/286 - capacitor plague?

Postby matze79 » 2016-3-20 @ 06:04

I got another LTE/286 working:

Image
Image

More Pictures here:
http://www.dosforum.de/viewtopic.php?f= ... =15#p64717

Same VIA defective as above, same capacitors.
All others make a nice fish smell..
need a replacment for them too. Hopefully they don't contain PCB poison.. :O
Unfortunaly they are soldered and glued to the pcb..
so its not easy to get them offboard

(Please correct me, if my english is wrong, grammars suffer.. i tend to use it like german words.)
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