View Full Version : What the heck does this switch on my kaypro2000 do?

January 12th, 2018, 02:31 PM
so there is a small slide switch located behind the left lcd hinge on the unit. See photo. What does it do? its near the power input and battery lines so I assume something with power or charging but what? I have two battery packs (the internal and the options external pack that came in a canvas pouch) which still manages to hold some juice. I just want to try and see if the unit has any life. I kind of get the feeling some tantalum caps may have already blown.

Anyway, what the heck does this switch do?42991

January 12th, 2018, 03:45 PM
Press it and find out :p

Is that actually a button?

I just looked at mine and mine does not have that. However, a little further behind that should be a lever switch that is engaged when the screen is placed in the "up" position. That is what powers the system on/off. It could be someone wired in an extra switch to act as a reset, or perhaps allow it to run with the the screen down.

BTW, does yours still have the lead battery pack? Mine does, the battery is dead but it just doesn't feel like the good old heavy kaypro without. :)

January 12th, 2018, 04:20 PM
I don't know what the switch does but I have two Kaypro 2000s (neither had a power supply so I have never powered them up :( ). Anyway, one has the same switch but the other does not. Interesting that some have them and some don't.

January 12th, 2018, 05:32 PM
this youtube video makes mention of the switch. https://www.youtube.com/watch?v=pXpbQEtIafU

so anyway, my kaypro 2000 didnt have an AC either... (how can there be all these kaypro laptops with no AC adapters?)

I bought the external battery pack off ebay (comes in the cloth case) I am using my fathers old 1970's era Sears automotive battery charger since it has a 6 and 12 volt option and 1.5 or 10 amp switch too. Im using 6 volts at 1.5 amps to charge the external batttery pack. After 30 something years, It holds a slight charge.. Today for the first time I was able to see it post! it boots, counts the 640KB Ram, Bios rev and date are 1.08X 11-14-1985 it then says no valid boot disk is inserted and clicks a couple times asking for a boot disk and to push any key to continue. Oh yeah, this unit came with the original disk spacer for the floppy drive!
SomeGuy my kaypro 2000 still has the internal batteries. I want to pull them and see if I can wake htme up with the charger too. Does anyone know what the exact power supply specs should be?

I dont know about this switch, I cant imagine half of the ones out there were modded. I think they came that way. Its bizarre.

January 12th, 2018, 05:36 PM
forgot to mention the LCD is so dim! I have to use CTRL-ALT-F2 a few times to make the contract darker but it is still dim at its darkest setting! ?Hope there is a way to fix that.

January 12th, 2018, 07:22 PM
Unfortunately, my power supply has no markings on it. It looks like it had a paper label on it at one time but it fell off a long, long, time ago. That is probably why the power bricks get lost - nobody knows what they are for and they don't fit in the carrying case.

Ah, so you snagged that external battery off of ebay. I was thinking about grabbing it myself, but the last time I tried to power up my Kaypro 2000 something else had gone wrong with it. It looks like that is the same battery they used internally, so if your internal battery is dead you might be able to swap it.

The power supply is a simple DC power brick. I THINK it is supposed to be ~5 volts DC, but when I tried to measure mine I got some odd results. I think it needs a load on it.

Actually - test you external battery after it is charged and see how much voltage it is putting out.

A word of warning: The Kaypro 2000 internals have NO protection against too much voltage or negative voltages. So if you get the voltages wrong, you can smoke the entire thing. Someone on Youtube did that. I'm not even sure if there is any power regulation inside.

The internal battery itself is just wired directly to the DC power. No circuitry other than a fuse!

Nope, the LCD screen is just plain dim. I think some of the much later models had a backlight. All you can do is position the laptop against some good lighting.

January 12th, 2018, 07:34 PM
yeah Im the one who got it off ebay. Told the guy I wasnt gonna pay anywhere near full price because the cells are 30 something years old. I got it for a fair price.
well its been charging for a few hours and its putting out 6.05VDC according to my fluke. Ill try some trickle charging tomorrow too. the batt was pretty warm as well.

January 13th, 2018, 05:52 AM
Ok, I tested my power brick with some different loads on it, and it reads a hair more than 6 volts (it reads much higher with no load, which is not right). Since there is no marking on it, I'm still not 100% confident, but that is close. The round plug has ground on the inner part, and positive power on the outer part.

The kaypro 2000 user guide states "The KAYPRO 2000 operates from one of two power sources : an external 120V AC wall outlet, or the internal 7V DC battery pack.", so certainly no higher than that.

January 13th, 2018, 06:32 AM
This picture is from this Kaypro 2000 eBay listing. https://www.ebay.ca/itm/192357655428 That should answer the question. I have been looking for one for a while but I may just try a 7.5V 2A wall wart and see if that works (like this one https://www.ebay.ca/itm/3112361443737 ).


January 13th, 2018, 07:01 AM
Snuci, I just saw your post this morning but your second link ( https://www.ebay.ca/itm/3112361443737 ) says the posting was removed.. So I dont know what it was. Can you send another example. Id love to find some kind of power source for my unit.

SomeGuy, are you saying the centerpost is negative??!! Thats stupid! I hate when they do that... didnt the round power port Vic20 also have that issue?
the battery pack was down to 5.24VDC this morning, doing some more charging on it right now. The kaypro is on, connected to the ext battery pack. I have jumper leads connected to the battery packs break away connectors and that is where I clipped on the battery charger. its jumping around 6.5vdc right now. I havent taken the kp2000 apart to see anything yet so I dont know the charging circuit. I know everyone says its "nonexistant" but it seems there is no charging happening with the onboard battery pack. When I open this thing up in a few weeks Im going to try some high amp charging and see if I can wake it up or kill it in the process (who cares its most likely dead)

January 13th, 2018, 07:17 AM
VERAULT, try this one: https://www.ebay.ca/itm/332509410759 The main thing is that it does 7.5VDC at 2 amps.

January 13th, 2018, 07:22 AM
thanks snuci, I can see that one. Is SomeGuy right, are the polarities reverses for the kaypro 2000 barrel jack?

January 13th, 2018, 08:28 AM
Thanks for posting the picture of the powersupply, I'll print that label out and put it on mine.

Yes, the center post is ground (negative). You can, and should, sanity test this yourself by doing a continuity test between pin 7 of the serial port (ground) and the center pin of the power socket on the back. There will be full continuity. Note that the metal shield around the serial port may not be grounded.

I can't find a graphic of that off hand, so here is some quick ascii art

+ --| O---- Ground/Negative

7.3 VDC 2 AMP

January 13th, 2018, 08:59 AM
yep, i have continuity between pin 7 and centerpole..... Terrible engineering. Anyway, further tinkering is going to have to wait I accidentily blew the SFE9 fuse in the ext battery pack and I dont have any more. I might have some 5 amp ceramic ones somewhere though....

January 13th, 2018, 09:28 AM
BTW snuci I bought that adapter.....

January 13th, 2018, 10:15 AM
Let me know how it works out. I'm interested in finding out if there are any operating problems at 6v, or if 7.5v is too much "7.3v" seems oddly specific - I'll let you let your magic smoke out :p

If that Kaypro 2000 got a lot of use then the internal battery would certainly be dead, even if it was always used with wall power.

It would be an interesting project to see if a "modern" rechargeable battery of some type could be fitted in the compartment and wired in. It would certainly be a lot lighter, and might even run longer.

January 13th, 2018, 10:35 AM
Guess Ill be the guinea pig...... YAY! Yeah Im just going to get the voltage and reverse the polarity and fire up the new AC and hope for the best (I mean its a cool laptop, but its certainly not my prized possesion)

I was toying with the notion of building a new battery pack for 6.5V for it. I only attempted to do that 10 or so years ago with very bad results so I havent tried anything like that since.

I mean this thing uses huge lead acid gel batteries. Can I just use a similar size 6 volt setup with modern lithium packs and thier own charging circuit rather than reinvent the wheel. All documentation says this thing doesnt even have it own power circuit, its all just direct wired in.

January 15th, 2018, 01:16 PM
VERAULT, try this one: https://www.ebay.ca/itm/332509410759 The main thing is that it does 7.5VDC at 2 amps.

snuci the adapter I bought off ebay was delivered in less than 48 hours! Looking forward to testing it this weekend.

January 19th, 2018, 11:03 AM

So the adapter arrived that I bought off ebay. And it came in an amazon box, dont you love that when you realize you could have found it cheaper on amazon and you paid someone else extra money for no reason!?
Anyway, I couldnt see it on the ad when I ordered it but the multi tips are not reversible! They ahve a thicker post for postive. Luckily I have an old 80's or 90's radio shack multi tip from an old universal psu I used to have and both posts are the same. I set the unit to 7.5Vdcs and tested it and the kaypro 2000 posts with only the AC adapter! YAY. The tip isnt perfect though so I am going to contact the seller, as much good as that will do. I hate how they dumb these things down so you lose functionality. I dont care if someone blows thier electronics because they didnt check polarity! dont punish me for it!

January 19th, 2018, 11:16 AM
https://www.amazon.com/CUGLB-Regulated-Universal-Switching-Speakers/dp/B01CFJH2U4 I paid $7.82 More! Damned stupid impulse buys!

January 21st, 2018, 06:12 AM
fyi there is a center negative version of that

February 19th, 2018, 05:47 PM
fyi there is a center negative version of that

ITs even a better price! I wish I had known that! Its moot at this point and I already have a working AC.

February 19th, 2018, 05:49 PM
On to the next idea, since I have that kaypro external battery pack. I think these would work nicely to replace the 3 d cell lead acid batteries.


And if that works the internal 3 as well. Anyone have any ideas for wiring it as to make sure it wont cause issues or burn up?