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Kaypro II Power Supply Ratings

glitch

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I've got a Kaypro II with no power supply, what current ratings do I need to satisfy to shoehorn a modern switching supply in there?
 
Kaypro Power Suppy Info

Kaypro Power Suppy Info

INFORMATION from my Maintenance Manual:

Kaypro used three different brands of Power Supplies. They are interchangeable with any of the Kaypro Computers. The Power Supply are Astec, Boschert, and Cal DC.

EXCPETION:
If a Power Supply is removed from a 2/83 or a 4/83, and it's going to be used in another computer, it must be used in a 2/83 or 4/83. The Power Supplies used in 2/83 and 4/83
computers are not interchangeable with other Kaypro Computers.

ASTEC Power SUpply:
Identified by a beige board with a white label on the right of the component side.

Picture in my book shows:
ASTEC Model AA12350
Output 65 Watt Max
+5 VDC 5A
+12 VDC 3.5A
-12 VDC .25A

BOSCHERT Power Suply
Identified by the word "Boschert" on the Component side of the board at lower right and above the fuse anc capacitor C2.

CAL D.C. Power Supply
Identified by a bright blue circuit board. A white sticker with "California DC", Model, and Serial Number is located on the solder side of the board.


Astec
1101 Space Park
Santa Clara, CA 95050
408.727.3350

Boschert
384 Santa Trinita Avenue
Sunnyvale, CA 94086
408.732.2240

Cal DC
2150 Anehor Court
Newbury Park, CA 91320
805.499.3621

The address info is probably way out of date. Google for more Info on them.


Hope this helps.

Larry
 
Last edited:
Some more info

Some more info

Also go to bitsavers for a copy of the manual
& search this site for other info in the knowledgebase we developed - there were some soldering issues with some of the power supplies.

Be aware of the possibility of some lethal voltages - so also check this site for them

You may want to use someone who is knowledgeable in electronics.

Good luck !

Please keep us informed of your progress so we can add to the knowledge base.

Frank
 
Frank,
THANKS for the tip on bitsavers. I wasn't aware of it.

Do you know how one makes contributions to bitsavers? I didn't see any information on how to contact the folks there.

I've got some Floppy Drive Manuals that might be of help. I've also got a Document on installing and using 3.5" Drives
on Radio Shack Model 4 Computers, Kaypro's, and my Ampro "Little Board Z80".

Thanks.

Larry
 
Eight years later, I'm finally fixing this particular Kaypro! And this is the first result when searching for Kaypro PSU ratings :)

A Mean-Well RT-85B is looking like a perfect match. I've got one on order and will report back on how well it works in a Kaypro II. Ratings are probably conservative enough for even the Kaypro 10.
 
In my Kaypro 4/83, in which I have added a 10 MB MFM harddisk + controller, I put in a MW MPT-120B Triple Output supply.
It is almost a perfect match only slightly less length (needed to drill two new holes). I could even reuse the original Kaypro connector.
 
In my Kaypro 4/83, in which I have added a 10 MB MFM harddisk + controller, I put in a MW MPT-120B Triple Output supply.
It is almost a perfect match only slightly less length (needed to drill two new holes). I could even reuse the original Kaypro connector.

Nice! The Kaypro chassis would be a good place to use one of the open frame modules, since the original was anyway.
 
In my Kaypro 4/83, in which I have added a 10 MB MFM harddisk + controller, I put in a MW MPT-120B Triple Output supply.
It is almost a perfect match only slightly less length (needed to drill two new holes). I could even reuse the original Kaypro connector.
Thanks for the tip. My Kaypro II Astec AA12350 power supply seems to have died after the main RIFA smoked and I replaced all 3 RIFA's. So I managed to find an MPT-120B locally in Australia very cheap on clearance after finding this thread so will go with that option.

How did you end up reusing the original power connector? Switch pins, cut?

Also, where did you find a suitable hard disk controller?

Cheers
 
glitch i have a spare kaypro psu as well as other kaypro spare parts send me a pm. Funny seeing this thread. i Fired up my kaypro II i got from radracer203 a couple years ago the other day to test the cpu feom a zx sprectrum 48K IM REPAIRING. i wanted to try the cpu in the kaypro II but it shorted 2 seconds after i started it. in the past day i recapped the psu and the crt boars.. turns out the upper floppy drive was the culprit. either way send me a pm. I can gurantee it works.. be willing to trade for an XT ide if you have one.
 
Thanks for the tip. My Kaypro II Astec AA12350 power supply seems to have died after the main RIFA smoked and I replaced all 3 RIFA's. So I managed to find an MPT-120B locally in Australia very cheap on clearance after finding this thread so will go with that option.

How did you end up reusing the original power connector? Switch pins, cut?

Also, where did you find a suitable hard disk controller?

Cheers
The Kaypro 4/83 and 4/84 have a builtin HDD controller. The Kaypro II does not. If you can find one there is a 8088 DOS upgrade system consisting of 2 cards. Use your machine as an Early MS DOS computer. Whenever they come up on eBay its usually just one of the cards not a complete set.
 
The Kaypro 4/83 and 4/84 have a builtin HDD controller. The Kaypro II does not. If you can find one there is a 8088 DOS upgrade system consisting of 2 cards. Use your machine as an Early MS DOS computer. Whenever they come up on eBay its usually just one of the cards not a complete set.
Thanks for that info VERAULT. The reason I was looking for a hard disk controller is that I was exploring connecting up a FreHD to my Kaypro II as I assumed you still needed a HD controller but I now know you don't. And as you appear to be all too aware (I saw your attempts on a couple of threads), integrating a FreHD into a Kaypro II is either very difficult or maybe impossible without all the correct bits and info. So I am yet to decide if I want to give it a go.

Regarding the power supply, I managed to source the last remaining Mean Well MPT-120B in Australia it seems :) . I connected it up after realising it can in fact use the same power connector as stated above by gertK without any reconfig of pins but you do need to remove the AC Live Neutral and Earth pins and connect those to the separate header on the MPT-120B. It all worked and then the vertical deflection on the CRT collapsed so now I have another problem to solve.

I'll start my own Kaypro thread with my various problems to solve and mods to do so I don't keep digging up old threads, even though they have some valuable information which could be lost otherwise.
 
Thanks for the tip. My Kaypro II Astec AA12350 power supply seems to have died after the main RIFA smoked and I replaced all 3 RIFA's. So I managed to find an MPT-120B locally in Australia very cheap on clearance after finding this thread so will go with that option.

How did you end up reusing the original power connector? Switch pins, cut?

Also, where did you find a suitable hard disk controller?

Cheers
Sorry for the late reply.

I cut the original connector in two parts (AC and DC) and then the separate parts matched the layout of the pins of the MeanWell supply.

The harddisk controller is a homebrew adaptation of an ISA 8 bit controller from WD. I needed to write my own drivers though.
 
The Kaypro 4/83 and 4/84 have a builtin HDD controller. The Kaypro II does not. If you can find one there is a 8088 DOS upgrade system consisting of 2 cards. Use your machine as an Early MS DOS computer. Whenever they come up on eBay its usually just one of the cards not a complete set.
The Kaypro 4/83 here does not have a HDD controller, nor a connector or pads to connect one. I ended up connecting an ISA 8 bit MFM controller with a small ratsnest of cables and a self-written driver.

The 4/84 have a connector (sometimes only pads) to connect a MFM controller.
 
Sorry for the late reply.

I cut the original connector in two parts (AC and DC) and then the separate parts matched the layout of the pins of the MeanWell supply.

The harddisk controller is a homebrew adaptation of an ISA 8 bit controller from WD. I needed to write my own drivers though.
Thank you. Yes I was amazed that when I actually got the new power supply in my hands it was actually pin compatible except for needing to cut the connector. I wasn’t going to cut it as I like to keep everythhing original but can still be used with the original power supply if I ever repair it. Have not been well lately so will get back to it all soon.
 
Thank you. Yes I was amazed that when I actually got the new power supply in my hands it was actually pin compatible except for needing to cut the connector. I wasn’t going to cut it as I like to keep everything original but can still be used with the original power supply if I ever repair it. Have not been well lately so will get back to it all soon.
Firstly, hope you are feeling better.

Wonder if you got around to finishing this up as yet? I have a 2X that was failing and have tracked it down to it's power supply. (Well, I am 99% confident that's the problem.) I encountered this thread and another that recommended the Mean Well T120B SMPS.

In searching eBay, I came across this type that had "pin outs" (actually screw lugs) similar to the pin outs on my defunct PS and wanted to verify that this would be suitable. Here are the connections:

Mean Well T120B connections.png

Also, here are the ratings -- that seem to be adequate:

ratings of T-120B from Texas.jpg

The dimensions are well within the footprint of the old PS and I do not mind savaging the existing Molex connector and replacing the connectors with spade lugs. I originally did a diagram of the rat's nest wire harness to clear things up and now have expanded it to include the conversion to the T120B PS (attached) if anyone is interested.

I have a T120B on order from China and will proceed to experiment. If any comments or corrections, I would be obliged to hear of them.
 

Attachments

  • Visio-Kaypro Wire Harness Diagram.pdf
    156.3 KB · Views: 19
>> I do not mind savaging the existing Molex connector and replacing the connectors with spade lugs
Another option is to make up a cable to connect to the existing Molex connector and crimp spade lugs on that to connect to the new power supply.
 
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