Kaypro II CRT adjustment help

[r34per]

Finally resurrected my Kaypro II and got it booting cpm. The last thing I wanted to try tackling is getting the display on it adjusted a bit. The image was pretty scrunched, and I used the adjustment knobs on the controller board to make it look more normal. I got it mostly good, but the very top and bottom(more on the top than the bottom though) still seem a bit scrunched compared to the middle no matter how much I adjusted the v.lin and v.height knobs. It's not too bad, and I can deal with it but if there is another adjustment I can make to even it out I'm willing to try it. The corners are also a little blurry, I got it a little better by turning the focus knob though. I know that to an extent that's just how crt's work, but is there something I could do to bring them in focus a bit more? Would adjusting the yoke help with that?

And lastly, and probably the most apparent is that the display seems to "wobble" or "jitter" sometimes. It seems to happen more often when there's activity on the floppy drive but it also just happens when it's doing nothing. The crt and controller board in mine is a toshiba if that helps at all.

Grateful for advice on any of these things, thanks!

 

[VERAULT]

There are some pots on the CRT analog board but they are really hard to get to. You want some plastic CRT tweaking tools with extensions. Amazon sells them pretty cheap I can send a link if youd like.

As far as the wobble mine do that as well. I figure either the PSU needs a recap or the analog board does, but as long as they work I am not inclined to do the recap.

but in truth the CRT's lack some of the other tuning pots most full size monitors have. Get it as best you can. Adjust the yoke with pretty much just help center the image, not much else (centering rings). I am not sure if there is a focus pot on the kaypro CRT.

I wonder if the B+ voltage is off thats why the edges are blurry.

Does anyone have pdf copy of the chiltons kaypro repair manual (or was it haynes)?

 

[tyhoeffer]

It was Chiltons. I have the book, but there are only about 3 paragraphs on the Video unfortunately. There is a PDF document out there for the "ELSTON" CRT board.
Northstar used the elston board & the "00464B_Northstar_Advantage_Technical_Manual_1981.pdf" at https://1library.net/document/z11g09dz-b-northstar-advantage-technical-manual-pdf.html
manual has schematics. Elston has a document covering that board as well "Elston_DM30_DM40.pdf" at http://www.bitsavers.org/pdf/elston/Elston_DM30_DM40.pdf

My Kaypro 4/84 has the Micrex board, and I have found nothing on it. The circuit is quite similiar, so if you have a decent understanding of electronics the ELSTON schematics can help you repair if needed.

My Micrex board had Severe Vertical issues, ( screen wrapped back on itself, but a full Re-Cap of all the electronics fixed it right up.

Ty Hoeffer
Palmyra, VA

 

[acgs]

Does anyone have pdf copy of the chiltons kaypro repair manual (or was it haynes)?

Any member of VCFed can have a copy of the PDF as mentioned in this thread (skip to post #56 for the quick version):

https://forum.vcfed.org/index.php?t...pair-and-maintenance.68104/page-3#post-861992

And the real final say on the subject starts here:

https://forum.vcfed.org/index.php?t...to-kaypro-repair-and-maintenance.68104/page-4

Proving that it pays to ask nicely

 

[r34per]

Good to know! Sounds like the kaypro service manual I have has about the same amount of info on crt adjustment. It very well could be in need of a full recap honestly, one of the electrolytic caps on the crt board was dead and shorted which was why no image came up when I got it. Seems like a good book to have though, I'll shoot him a PM for a copy, thanks!

Really though, I've other projects I'd like to get to and finally get this kaypro ii off my workbench(been sitting there in pieces for a few months now!), so I think I'll just tinker a bit more with the v.lin and v.height to get it "good enough" until I have time to do a full recap. I can get it mostly even other than the very bottom row still being a bit squished. None of the caps are leaking or bulged, so it's most likely fine for the time being. Unless those with more knowledge on these kaypro ii's has some sage wisdom to pass down on some components that should be replaced asap, rifa caps on the PSU aside which I took care of already.

 

[SteveHere]

Thanks @tyhoeffer and VCFed community. I was able to bring back a non-functional Kaypro II based on this advice. Mine has a Toshiba branded CRT and Toshiba 23879862 TLC-134-T-V-O Analog Board. The CRT was showing signs of life (heater OK, High Voltage running), but I couldn't get any raster. Based on the feedback on this thread and some YouTube videos I did a complete recap on the Analog Board and that fixed the issue, I was able to adjust the CRT and the Kaypro II 82 is working now.

A Kaypro II from 1982

My latested repair story is about a Kaypro II from 1982. The Kaypro machines have such an odd numbering scheme. They used Arabic numerals ...

writtenoutput.blogspot.com

 

[VERAULT]

Thanks @tyhoeffer and VCF community. I was able to bring back a non-functional Kaypro II based on this advice. Mine has a Toshiba branded CRT and Toshiba 23879862 TLC-134-T-V-O Analog Board. The CRT was showing signs of life (heater OK, High Voltage running), but I couldn't get any raster. Based on the feedback on this thread and some YouTube videos I did a complete recap on the Analog Board and that fixed the issue, I was able to adjust the CRT and the Kaypro II 82 is working now.

A Kaypro II from 1982

My latested repair story is about a Kaypro II from 1982. The Kaypro machines have such an odd numbering scheme. They used Arabic numerals ...

writtenoutput.blogspot.com

Good Job Steve. Post some photos.

 

[SteveHere]

You bet, here's some pictures, first, the analog board with my cap list...

My handwriting is not great, so in case any one else is going to recap a Toshiba 23879862 TLC-134-T-V-O Analog Board here's a list of the Electrolytics on the board...

C423 = 47uF 16V
C412 = 100uF 16V
C403 = 2.2uF 50V
C301 = 4.7uF 50V
C308 = 10uF 16V
C302 = 33uF 16V
C443 = 47uF 35V
C441 = 47uF 35V
C404 = 100uF 16V
C304 = 1uF 50V
C305 = 10uF 25V
C311 = 47uF 25V
C309 = 220uF 10V
C415 = 47uF 160V
C413 = 22uF 160V
C310 = 1000uF 16V
C430 = 6.8uF 50V Bipolar

Then, when I got the caps I had on hand in, and saw raster for the first time on the screen...


Then, after replacing the remainin caps and adjusting the CRT, the completing the repair...