Quote:
Originally Posted by PJL
It would be an easy test just lifting one end of R41 & R42 (27 ohms) and linking the lifted end across to the opposite resistor hole.
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Yes, I've already described this, from a document on Zimmers? website, a few posts ago.
However, they've already said they don't want to be confused by requests to try many other options at this stage, but to try and work through it in steps from one person.
Having to post updated EPROM's can delay progress a bit, due to not having direct-access to their own IC-programmer (An Arduino / RPi 5V-only one could be quite low cost, if got these) and some DIL 5V parallel FLASH / EEPROM IC's (as it would have been quite easy to have attached various customised diagnostic routines here, to update these with)
- It's a pity that the Dave Roberts PETTESTER V04 EPROM appeared to be staying in its screen-RAM Test routine's repeat whole test in an endless loop on readback-failure (seemingly because it couldn't read this back correctly, even though the first 1000bytes on screen looked at). As this did seem to have a good, full-reporting test of Zero-page etc. Main-RAM from looking through the source code, that would enable you to wrk out exactly which RAM IC(s) weren't working.
So maybe a future V05 (it seems it has been updated a few times recently) of that could time out on screen test (especially if it seems to be mostly working) and try the main-RAM as well. And I presume you can't rely on keyboard / other Inputs working, to be able to control it via a menu etc. If anyone's in touch with him on the vcfed etc. forum, then maybe could make the suggestion to him, rather than potentially hacking the source and re-assembling ourselves to produce different versions to sending to others.
But once all the faults have been identified with Colin's PET (It does appear there's an screen RAM fault lurking somewhere, that doesn't seem to show on the screen - other than now gone? '+32' issue. But it will be much easier to find this from a BASIC program etc., once main-RAM works enough to boot into BASIC), then knowing the exact faults could be useful for determining how future diagnostic versions will work best.