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  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: ..."
http://bitsavers.trailin...copia_%252323_Apr85.pdf

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.

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