Kaypro / Hardware / Part 2


Kaypro hardware

<-- Back to Part 1: Revisions and versions


model name MHz FDD FDD HDD
II/83 2,5 2x SS/DD, 191K h, fh -/-
4/83 2,5 2x DS/DD, 392K h, fh -/-
4/84 4,0 2x DS/DD, 392K h, hh -/-
10/83 4,0 1x DS/DD, 392K v, hh 8,9M
2X 4,0 2x DS/DD, 392K h, hh -/-
10/84 4,0 1x DS/DD, 392K v, hh 8,9M
1 4,0 2x DS/DD, 392K v, hh -/-

v = vertical / h = horizontal / fh = full-high / hh = half-high / SS = single-sided / DD = double-density

Kaypro 10

Hard disk controller

The Kaypro 10/83 uses the WD1002-HDO (hard disk only) version. The floppy drive is connected directly to the mainboard (J8) of the Kaypro 10/83. The 1793-02 IC (U74) is used as floppy disk formatter/controller. In my case this is a SYP1793-002 from the SYNERTEK company.

The WD1002-HDO is a depopulated version of the WD1002-05. All Floppy drive control and associated circuitry has been deleted from the board, providing a Winchester Drive Controller board that will drive up to three 5 1/4" Winchester disk drives.
WD1002-05/HDO Winchester/Floppy Disk Controller OEM Manual
WD1002-HDO (61-031050)
Western Digital - WD1002-HDO (ASSY 61-031050)
Important note for ASSY 61-031050: It is essential to use a plastic screw for fixing at the bottom right hole (red arrow). If you do not do this, you might short-circuit the resistor R57 with the cabinet! If you mount the PCB, this hole is located on the upper left!

If you need to change the hard disk, it is best to use a Seagate ST225. The connection (MFM) is made via the two marked connectors. Your drive must be jumpered as DRIVE 1 (DS1); DS0-DS1-DS2-DS3!

You will immediately notice if the drive has been selected incorrectly because the FORMAT command cannot find the drive.

In the Kaypro, as far as I know, the ASSY (assembly no.) 61-031050 is used. Besides that I found another controller in the internet with the number 61-031093. This one is not from a Kaypro 10.

WD1002-HDO (61-031093)
Western Digital - WD1002-HDO (ASSY 61-031093)

Power supply unit (PSU)

Kaypro is using three different brands of power supplies at the present time. These are Astec, Boschert, and Cal D.C. These three power supplies are interchangeable with any of the Kaypro computers, if the power supply being changed is a new one from the factory.

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.
Kaypro Technical Reference, September 1985, Part Number 1484-F

If your power supply is defective and you have some craftsmanship, you can replace it with a Meanwell RPT-75B (triple output PSU: +12V, -12V, +5V). I am currently testing this.

... to be continued ...


Astec AA 12450
PSU - Astec AA 12450

You can use this power supply up to 55W or 75W (with cooling fan). In the meantime I have replaced the old RIFA interference suppression capacitors.

I have a second one of this power supply unit as a reserve.


PSU - Boschert XL60-3601

Floppy disk drives


Mitsubishi - FD5426A
Mitsubishi - FD5426A

This drive can be recognised by it's characteristic locking mechanism.

Mitsubishi - FD5426A
Mitsubishi - FD5426A

Besides the Mitsubishi - FD5426A there is also the Mitsubishi - FD5401A used in the Kaypro 10. The special thing about this drive is that the termination resistor is soldered and has only 150 Ohm. Kaypro's actually use 470 Ohm resistors.

Mitsubishi - FD5401A
Mitsubishi - FD5401A


Shugart - SA455
Shugart - SA455

You can recognise this drive by the screw hole in the locking knob.

Shugart - SA455
Shugart - SA455

Manuals and information

Data sheets

My series about the: Kaypro

--> Go to Part 3: 8K EPROM Modification