I didn't have a 5k resistor, so I used a 2k instead!!!!! I grounded all the pins (3,4,5,6,11,12,13,14) and found that pin 6 had the lease effect. If anything it just slightly solidified the lines that were already there. All other pins created new vertical lines. Phil On May 13, 2011, at 10:07 AM, Philip Lord wrote: > Hi, > I tried the step up transformer but that didn't seem to change anything. > I just tried RAM in I7, I8, J7 and J8...again, no noticeable change. I believe Ethan had checked all these ROMs as good, but I guess that didn't stop the CG ROM from going bad somewhere in transit between US and Japan. > I'll try the 5k resistor trick sometime today. I'll do this with the CG ROM removed so it'll be easy to see the lines. > > Phil > > > On May 13, 2011, at 9:08 AM, MikeS wrote: > >> Hi Philip, >> >> If you get that vertical line with the CG completely removed it is almost certainly a bit stuck low in B2, the 74LS165 shift register, or a short somewhere on the PCB around it. If you have a 5K or so resistor you could try shorting each of the pins (3,4,5,6,11,12,13,14) to ground through that; each one should add a line and the one that doesn't is presumably already grounded internally or externally somewhere. You may well also have another issue, but I'd start by checking for a short and/or replacing that chip. >> >> BTW, if you have four good spare RAM chips why not install them in I and J 7 >> & 8; if your ROMs are good that's all you need. >> >> Good luck! >> >> mike >> >> ----- Original Message ----- From: "Philip Lord" <random6000@mac.com> >> To: <cbm-hackers@musoftware.de> >> Sent: Thursday, May 12, 2011 4:30 PM >> Subject: Re: PET 2001 fix Part 3 - RAM/ROM board etc. >> >> >>> Hi guys, >>> It's early here (5:06am), so please excuse the brevity of my message as >>> I'll be going back to bed for a couple more hours after. >>> >>> I did change out the video SRAM as there were a few left over from the >>> main RAM that were still good. Unfortunately this did not change the >>> problem. Pulling the SRAM completely created a checkerboard effect, but >>> there were diagonal lines strafing through the pattern. I'll test this >>> again because at the time I didn't realize this was a valid testing >>> technique. >>> >>> Pulling the CG ROM takes the image back to its original state, blocks and >>> lines. >>> >>> One thing, late last night as I was briefly poking around with the logic >>> probe, there seemed to be many places where I probed that slightly >>> effected the pixel flicker. I didn't do much testing as it seemed a little >>> random and inconsistent. So maybe as Mike mentioned, it could be a power >>> issue. I have the board out on my desk hooked up to an original spare US >>> PET 2001 transformer. Maybe there is some issue with it being a US version >>> on 100v Japanese power. I think I have a JPN to US power step up converter >>> somewhere, maybe I'll try to find that. >>> >>> Thanks again >>> >>> ZZZzzz... >>> >>> >>> On May 13, 2011, at 4:31 AM, MikeS wrote: >>> >>>> >>>> ----- Original Message ----- From: "MikeS" <dm561@torfree.net> >>>> To: <cbm-hackers@musoftware.de> >>>> Sent: Thursday, May 12, 2011 3:28 PM >>>> Subject: Re: PET 2001 fix Part 3 - RAM/ROM board etc. >>>> >>>> >>>>> Looks like the problem is mostly in the fifth character column; wonder >>>>> if >>>>> that's where the horizontal line was originally? >>>> >>>> D'oh! VERTICAL line of course... >>>> >>>> Message was sent through the cbm-hackers mailing list >>> >>> >>> Message was sent through the cbm-hackers mailing list >> >> >> Message was sent through the cbm-hackers mailing list > > > Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing listReceived on 2011-05-13 02:00:25
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