Reply 16260 of 27457, by creepingnet
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- Oldbie
Not been very active with Vintage computers up until a few days ago because our lunatic neighbor lady finally moved away....so I've been spending over a few months dealing with that and chasing rental houses which amidst COVID-19 has been a royal pain in the rear....looks like the urgency to move is no longer here (don't ask why....that lady was a nightmare).
Since her leaving....I've got a NEC Versa M75 on the way with some weirdo parallel port thing called a Commpac Words+ System 2000. It looks like it has the typical Versa issue of cracking plastic (easily disguised by JB Weld and prevented with a healthy cleaning and dose of STP Axle grease to the hinge). The whole point of me picking it up though is I've been dabbling in Official Hamster Republic RPG Creation Engine and wanting to use it for MIDI. It also means I get another 220MB HDD.....might be fun to put OS/2 2.1 with Win OS/2 and Multimedia Extensions on after I backup all the stuff.
I've almost completely reverse engineered the NEC Versa OP-570-4401 and OP-570-4001 NiMH 3800mah battery packs. I've gotten two of them to charge, though one is bulding now so I'm stopping use until I get some new replacement "A" 1.2v NiMH cells to re-populate. I've blown up 3 cells thus far.
The basic design...as best as I can describe without ripping one apart....is this....
4 Contacts (Left to Right, label side up): - back cells, - front cells, charge sense, + (both packs)
The pack consists of 12 "A" NiMH cells at 1.2v each, and they are packed into 6 "sticks" (turquoise cardboard casings with rubber short protectors on the + end)
The electrical flow goes - terminal, to negative of the first 2 cells, then the postive for the first two cells goes through a Thermal cutoff set for 90 degrees, into the next 2 cells negative terminal, which then exits the positive terminals into a Thermostat for I thikn 100 degrees (Isuzu branded), then into the last pair of cells, which exits to the positive terminal on the battery that powers the laptop computer - there are 2 sets like this sharing a common positive. (remember, electricity flows from negative to positive).
The original pack for the 40EC somewhat works, I find if I turn the brightness down I get about 5 minutes of battery life out of it. However, the other pack I think I messed something up on and probably will need to replace the power board (again) in the 40 EC because the working battery is beign errant now and saying it's full when it's not when the laptop is powered on. Luckily I can find one.
The one component I'm still trying to figure out is the doodad in the picture that measures 10K ohms, at first I thought it was a resistor, but I think that MIGHT have been what killed the other pack.....
The other pack had that part burned up in it, like burned up so much it no longer exists, so the battery would not address when attached. So I crossed my fingers, soldered in a 10K ohm resistor, and it seemed to do the trick. Under both batteries I got about 10 minutes of battery life with the contrast fully down. Seemed like I was on the right track.
However, the next monrning, both batteries had self-discharged from a full charge, and I found the one I fixed the night before after putting it in the laptop again....started making weird noises....so I took it out....it started fizzing, then I heard a loud "POP" while I was in the other room......then I heard it fizzing some more, escalating fast, then another loud "POP!!!" and the case split open...and STILL fizzing, so I threw a washcloth over it and grabbed it with BBQ tongs, and left it outside on the pavement all day while I was at work.
So I came home and replaced the two cells that had popped rather violently with the best ones from another pack. Well.....I started running and charging that battery pack again...still with the 10K ohm resistor. I found it WILL behave in the laptop properly as far as charging and showing proper status, but I also stopped using it immediatley because the non-exchanged cells started to expand toward the ends....and the last thing I want to do is damage more plastic on the Versa from another venting NiMH cell.
But yeah, if anyone knows what the circled component is I'd love to know. My other pack also got it's burned during this stuff (tried a full discharge and it fried it). I'm going to replace the power board beforehand. The reason I thought it was a resistor is because the part in the other pack seemes to be some hair-thin wire attached to an SMD component of some kind that measures at 10K ohms resistance. So either those cells in that battery are so old they are popping under load or charge, the resistor is the wrong part and they are getting over-charged, or both.
I'm not doing this with the M75 when it comes in though.....that one I think uses the "Smart Batteries" anyway. My plans for both batteries are to get all the right components, properly rebuild them with new cells, and then use them that way. Then when I'm done, I plan to see if I can come up with a newer, easy-replace battery version with no soldering involved that will be safe.
After the Versa stuff is all sorted out, I'm breaking out the Tandy 1000 AGain and working on my light pen some more. I just picked up a AMF Barcode Scanner that was mis-represented as a "light pen" and I rewired the end using a breadboard and a spade connected ATari 2600 controller cable to be properly powered by the Tandy's Light pen Port. I'm thinking I might even be able to hack this into a dual purpose Light Pen/Barcode Scanner combo unit. That'd be cool. But that's for another day.
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