KayPro video issues

[retrobecanes]

My KayPro is giving me only a very thin line in the middle of the screen when it turns on, as if the prompt to insert a disk in drive A was completely crushed. But despite that I can see part of that line that blinks (where the cusor awaits).
I have tried to adjust the image with the different pots on the CRT control board but nothing works. Then if I place another motherboard in that KayPro (one that works for sure), I get a single bright dot in the center of the screen, not even the line.
What could this be?

 

[ldkraemer]

What is the exact model of Kaypro, what is the Motherboard Number, and ROM Number?

Is the thin line all way across the screen or just a portion? How about a Photo?

Larry

 

[Pickelhaube808]

I am no expert in the electronics of CRTs but I would have to say this is related to the circuitry for the vertical deflection. If no pots are changing it, there is likely a bad component somewhere in that part of the circuit that is making it fail. I'd check capacitors first.

 

[retrobecanes]

It is happening on the KayPro II
The CRT control board was recapped and getting 12V.

 

[retrobecanes]

Here is a pic of the motherboard

 

[tradde]

Looks very similar to mine. Although on mine there are some empty sockets where yours has nothing. Same ROM too. I don't see anything suspect, but I am no
expert in that area. Sure looks like it's trying to display but it's scrunched down. Mine is a 2x though not a II.

 

[retrobecanes]

Ok I seem to have found the problem, a couple of cracked traces near the voltage regulators. The image looks better. There are still cracks somewhere as a little pressure on certain points of the board turn the image off. The search continues.

 

[tradde]

Hmmm, curious as to what would cause this. Someone flexed the board too much?

 

[ldkraemer]

retrobecanes,
Why don't you re-flow all of the solder joints for the Power connector J7. I use Kester
63/37 solder and it would re-flow those connections easily.

You Motherboard appears to be the 81-294-n Motherboard with a ROM of 81-292.

Larry

 

[retrobecanes]

So I am glad to report that all issues have been fixed. They seem to have been due to cracked traces on the CRT control board. All else works well. Thanks for your help!!!