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Poqet PC Repair

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gobabushka

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Joined
Mar 29, 2011
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45
Location
Palm Bay, FL
Ok, I just recently aquired a poqet pc handheld. All the books, disk drive, everything! Only problem is...It does nothing and the left hinge is broken. It looks like there is some corrosion in the battery compartment. Any ideas, disassembly guides? I would love to fix it!
 
gobabushka said:
Ok, I just recently aquired a poqet pc handheld. All the books, disk drive, everything! Only problem is...It does nothing and the left hinge is broken. It looks like there is some corrosion in the battery compartment. Any ideas, disassembly guides? I would love to fix it!
Click to expand...

While I don't have any first hand experience on a poqet (though its on my wish list), I will say super/gorilla/crazy-glue (cyanoacrylate) carefully applied will fix most handheld/laptop hinges, and if there's clearance to do so, I will usually glue on an extra bit of thin scrap plastic as sort of a splint to provide more stability (though I doubt there's clearance on a handheld).

Can't help on dissassembly, but I am sure there's someone here that has done it.
 
Well for starters, clean the corrosion off the battery case and off the terminals. The corrosion is probably preventing it from getting power from the batteries.
 
Most of the Poqets are relatively easy to disassemble. Just be careful as you go.

IF I remember correctly, there are a couple of screws under the rubber feet.

Disassembly varies depending on the model. There are actually 2 Poqets and 1 Poqet Plus. The Plus is significantly larger and easier to work on.

Not a whole lot you'll be able to work on tho as it's mostly surface mount devices.

Like mentioned above, first thing is clean the corrossion off the battery leads. That may actually resolve your issues. If not, check the battery leads make sure they're connected. Sometimes wires break!
 
Did you ever make any progress with this?

Did you ever make any progress with this?

gobabushka said:
When I get home, I'll try it and report back!
Click to expand...

I have an original Poqet PC that I just got. It doesn't boot. It just whines softly when batteries are installed, and, if you hold down the reset button, you'll get a one-pixel high line across the screen at a random location. That line will stay there as long as reset is held, and then go away.

BTW, no, they are not held together by screws under the feet. They are held together by plastic weld as Bryan Mason indicated on his FAQ. I was very surprised that there were no photos on the web of the internals of one of these things, so here are a couple. Looks like Fujitsu was actually the original manufacturer (a lot of Fujitsu parts inside, including the RAM chips). By the way, they have parity RAM... not sure why they bothered, as difficult as it would to replace a bad RAM, but I guess that was the tradition at the time.
 

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Parity's more than just about RAM replacement, it's about failure detection, though. If you don't know a bit was flipped, your data can be corrupted without you ever knowing. Especially back then, with RAM reliability not being so hot...
 
bhtooefr said:
Parity's more than just about RAM replacement, it's about failure detection, though. If you don't know a bit was flipped, your data can be corrupted without you ever knowing. Especially back then, with RAM reliability not being so hot...
Click to expand...

It's not about RAM replacement at all in these units. And yes, I do know about this stuff. I was repairing motherboards, power supplies, hard drives, etc, to component level back when this thing was new. My point was that having parity bits on SMD static RAM in a welded together unit is pretty pointless because you can't easily replace the RAM. Parity with DIPs, SIMMs, DIMMs, etc does give you an early warning and you can then fix it. Here you can't do anything about it, and a POST RAM check, or diag app would tell you quickly enough that the RAM (and, effectively, the whole unit) is bad. Adding the parity gives you the slightly earlier warning while also giving you a 12.5% higher likelihood of failure (since there are now 1/8th more RAM chips that might fail. They might as well have saved the money, power, and real estate.

Now, if they had had a way to map out bad bytes, or chips, and use the extra ones as hot spares, that would be a different story.... but I kind of doubt that for this age of a unit.

On the other hand, as I was writing this, I remembered that:
A) There was a variant called the Poqet PC Prime that had 640K - this one, however, has the P/N of the 512K Classic, not the 640K Prime.
and
B) Besides the main memory, there was also a 22K RAM drive. I don't see other obvious RAM on the board. I was thinking that the 834000A-20 might be SRAM, but it's actually 512KB of ROM. So, it seems likely that that 22K is coming out of the additional 64K provided by the two "extra" 32Kx8's. The rest must be some sort of working memory... maybe the video bitmap space.
 
What I've found so far is that there don't appear to be any electrolytic caps in the unit... they're all monolithic or maybe tantalum. The power supply seems to be mainly a couple of BI 8B105 DC/DC converters. I can't find a data sheet for these. The 3V from the batteries is being converted to 5.2V (seems a bit high) for logic chips, and maybe +/- 10V or so for the RS232 interface(?).

Nothing obvious wrong. Current draw is about 150mA from the batteries, which seems reasonable.

Need to break out the scope next, I guess, and see what else I can find. I don't think there's anything under the keyboard as far as components, so I'm not sure whether I should remove it... looks like a pain to remove. I'm guessing that the three blobs cover the CPU and probably a couple of LSI chipset chips to cover UART, PIC, DMA, PCMCIA, etc.
 
OK. One more update, though I'm probably running out of options unless I can rig up some sort of POST card or something for this thing:

1. I removed the keyboard, and, sure enough, there are no components under it... just the contact pads for the keys. I wanted to check anyway in case there was damage or corrosion underneath. It's clean, though.

2. Only one of the 8B105's seems to be powering up. It seems to be generating 5.2V, 10V, and -10V all by itself. The other one (on the back side), seems to stay off.

3. The unit draws about 140mA normally, but if I hold reset it drops to 130mA, and then, when I release it, it jumps to about 200mA for a few seconds before settling back down. This leads me to think that there's something that's failing pretty quickly in POST, and, either it's before it can enable video or a beep code, or its POST just doesn't do beep codes.

4. I see signals from the two crystals and at the sysclk pin on the XT bus. I don't see any other bus activity normally. I haven't rigged up enough of a harness to try to monitor the bus immediately after reset... and it's not something you can really do handheld, since all the components are on the back and reset is on the front.
 
Well, one more update. Turns out 8B105 = 628B105, which is actually a resistor array. I have been able to identify all other (non-blobbed) devices on the main board, and none of them are a DC/DC converter... the only item that clearly belongs in a power supply is an LM385-1 voltage reference. At this point, I have no idea where 3V battery power is being converted to 5V, and +/-10V (though, under one of the blobs, seems a likely candidate, especially since one of them does get slightly warm).

However, since I do have 5V (albeit noisy and slightly high), I'm thinking that PS is not the problem and it's failing somewhere in early POST. I'm thinking of bringing out the expansion connector to an ISA bus and then see whether a POST card will be able to read any codes from there.

One other thing I'll probably try, since it's quick, is tapping 5V from an external power supply directly to Vcc and seeing whether it runs from that.
 
I've ordered a backplane (Compaq Deskpro 4000) and a POST card. Looks like I should be able to cut off one of the narrow gauge card edges from the backplane to make a connector for the expansion slot on the Poqet, then wire that up to the ISA part of the backplane to have an external expansion bus for it. Not sure yet whether I'll pull power from the Poqet or provide it externally. For the POST card, I would expect the Poqet to provide enough power, though.

Looking through the Poqet expansion pinouts, it actually looks like it would be feasible to use external 8-bit ISA cards through such an arrangement... finding cards and DOS 3.3 drivers is still a bit of an issue, though...
 
Got all the parts a while ago, but haven't made the time to do much on it. I did cut off the card edges from the backplane, and the two 80 pin ones were exactly the right width for the Poqet expansion port. I cut the alignment notch in one of them, and it fits perfectly and makes correct contact for all pins. Next (long) step will be stripping a bunch of IDE cable wiring and soldering each of the needed pins to the backplane.
 
Hey SQLGuy, I've been waiting 5 years for an update!

My Poqet PC has the same symptom - 1 horizontal line of pixels at a random row when I hit reset.

Any luck getting yours to boot?
 
homebrew port

homebrew port

I'd be very interested in know whether anyone has been successful in making their own Cable Link for the Poqet. I read on another forum where a guy built one from an OLD SIMM. I rummaged and found one that seems to be perfect. But now I'm worried about how I should go about cutting it, as well as the best procedure to re-equip it for the new job. Hopefully some people are still around watching this section!
 
I just got a Poqet today.

Slapped in batteries, got a high pitched whine out of it.

Pressed Reset. One line.

Went HAM on Reset, wiggled, moved, pushed, wobbled, really gave it the beans...

Once I let go, the machine booted.

LCD has a few 'dead' lines at random spots from top to bottom. Wonder if it's a bad cable, cold solder joint, or the lcd itself is damaged.

Poqet.jpg
 
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