|Kaypro II||by Bill Degnan - 02/19/2022 19:57|
As soon as I saw this raised socket I knew this was not a stock Kaypro II, but other than raising the Z80-PIO chip what else is different? Click image for larger view.
This Kaypro II was donated to Kennett Classic and does not boot, disk drive is not detected. Should be fixable.
James Palic, the original owner of this portable computer writes:
"...Online Consulting is the name of the company that I and my partner started nearly 40 years ago after we left Dupont. Initially we sold Kaypro and other computer hardware. Someone showed us how to modify the boot ROM to have our company name show when booting.
Online Consulting is still around but we're now known by our DBA - ONLC Training Centers.
That particular Kaypro is a very early production model. We were one of the first to sell Kaypro's on the East Coast and had gotten an early version to familiarize ourselves with the product. Maybe that's why it looks a bit different.
We never made any modifications to it other than swapping out the boot ROM...."
The boot ROM has been altered, it says "Online Consulting" where it should print "Kaypro" to the screen. Click image for larger view.
View of the motherboard. A Z80 CPU system with MCM6665AL is a 64Kx1 RAM. Click image for larger view.
The Kaypro II with the outer chassis covered removed. The motherboard sits on top of the CRT. Click image for larger view.
|Mystery Restistor||by Bill Degnan - 03/05/2022 09:54|
Burned out resistor in location R21...but schematics show no resistor is supposed to be here. NOTE: Pink arrow or click for larger view.
I am trying to ID a burned-out resistor on this early Kaypro II motherboard so I can replace it. The schematics I found on the web do not seem to match and I can't locate the value of resistor in R21. See top near middle just to the right of the picture above.
I asked around to see if anyone has an early rev Kaypro II schematic to help ID the value of R21. I know later rev motherboards don't have anything in R21. I realize this might be a very early rev board and maybe just snipping the resistor will be enough, it was redundant perhaps?
Noting the burned out resistor in R21, one can make out the outer bands, but I am unsure if they're discolored.
* * *
ANSWER FROM MIKE LOEWEN:
".. It's a 10-ohm resistor, and shouldn't be necessary with normal printers. Just snip it out. Check out the Kaypro column on page 37 of this Micro Cornucopia issue: ..."
This issue is also available at Kennett Classic's library.
I actually had already snipped it, but given this is a resistor associated with the printer port, I did not expect it to fix the disk boot problem.
I also flip-flopped the disk drives, neither drive as "A" boots or attempts to even lower the drive head to read the disk.
NEXT - Having already flip-flopped the disk drives whatever the problem is, the motherboard appears to be the source of the problem. For example the drive controller / separator chip (FD1793B) or something connected to it.
|Replace Power supply||by Bill Degnan - 07/09/2022 00:48|
Ordered the replacement part described here:
NEXT - Install new supply