It sounds like the video clock circuit is not operating properly. Look at he horizontal and vertical drive lines, pins 5 and 3 on the video connector. See the top left corner of page 3 of the schematics. On Tue, 29 Sep 2009, Ethan Dicks wrote: > Hi, All, > > I'm in the middle of resurrecting a Static PET board (that I got last > year from MH Stein in (pre-warned) sad shape). I don't have an > original PET chassis at the moment, but I do have several enclosures > for 2001N/3032 16K/32K PET boards (pre-CRTC). The enclosure I'm > working on has a monitor that works perfectly with the 3032 board > Anders Carlsson sent to me at Pole. When I plug in the Static PET > board, I get characters, but not with the same "spread" across the > CRT. I see 25 rows, but they are about half as tall as I'd expect > (with large blank spots above and below). I do not, however, "see" 40 > columns. I see more like 25-30 columns, then the brightness of some > of them suggests to me that the remainder are "folded" under the > visible ones - a common problem back in the day with wonky video. The > chars are all sharp and stable - no tearing, no walking, no wobbling - > just not 40x25 filling most of the tube (unlike the perfect view with > the 3032 board). > > There are only two potentiometer adjustments on the monitor board - > brightness and V.Height. Both do the expected thing. I can crank up > the height with the 2001-8 installed, but then the 3032 display is way > too "tall". I can't fix the width or the H.Pos or whatever it is that > is causing the issue with the columns. > > I would expect that if there were a severe problem with the video, I'd > get sync problems or tearing or snow or pixel garbage. There's none > of that. > > I've looked around a bit, but the diagnostic information I've found > stops before the component level. Does anyone know of any in-depth > video repair info? I can't imagine there's a problem with the video > board since the 3032 display is flawless - am I wrong in thinking that > the video outputs from the 2001-8 and the 3032 are compatible if not > identical? > > Does anyone recognize these symptoms? Has anyone done chip-level > debugging of the video circuit on a pre-CRTC PET? I have the > schematics, naturally, but since so much works, I'm not sure where to > start. > > Thanks for any suggestions. > > -ethan > > Message was sent through the cbm-hackers mailing list > wlevak@sdf.lonestar.org SDF Public Access UNIX System - http://sdf.lonestar.org Message was sent through the cbm-hackers mailing listReceived on 2009-09-30 06:00:03
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