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  • SiriusHardware's Avatar
    Yesterday, 04:20 PM
    Gents, If daver2's 'Flying Doctor' visit results in this issue being solved I hope you'll update us all as to what the problem turned out to be.
    56 replies | 1811 view(s)
  • SiriusHardware's Avatar
    May 10th, 2017, 02:01 PM
    So there is. That one looks like it is involved in generating part of the video blanking signal. You seem to have good stable sync so I wouldn't have...
    56 replies | 1811 view(s)
  • SiriusHardware's Avatar
    May 10th, 2017, 09:39 AM
    Well done, that man. Nice work with the EPROM to PROM pinout converter. I sent a reply to your PM (which see) before I read this post. The...
    56 replies | 1811 view(s)
  • SiriusHardware's Avatar
    May 8th, 2017, 01:46 PM
    OK, just another word in here - the way I read it, you weren't quite sure that the EPROM to PROM adaptor trick was working when you originally tried...
    56 replies | 1811 view(s)
  • SiriusHardware's Avatar
    May 6th, 2017, 02:57 PM
    Since your memory address decoder PROM proved to be toast, is it worth trying a similar test on the I/O address decoder PROM to see if it is OK? The...
    56 replies | 1811 view(s)
  • SiriusHardware's Avatar
    May 4th, 2017, 09:45 AM
    the 27C040 is quite a modern device, so I would have thought it would come in at an acceptable speed for this purpose. When I said use the fastest...
    56 replies | 1811 view(s)
  • SiriusHardware's Avatar
    May 2nd, 2017, 11:36 AM
    Sorry, can you just clarify - by 'nothing' you mean... what? That both pins stayed high / logic 1, regardless of the input pattern? Or do you mean...
    56 replies | 1811 view(s)
  • SiriusHardware's Avatar
    May 2nd, 2017, 10:16 AM
    I think you said you had an eprom programmer? In that case the easiest way to 'fake' the PROM for testing purposes would be to program something like...
    56 replies | 1811 view(s)
  • SiriusHardware's Avatar
    April 28th, 2017, 10:06 AM
    Fair enough, although I think the D0-D7 outputs will be programmed to be normally HIGH and will go LOW to select their specific devices.
    56 replies | 1811 view(s)
  • SiriusHardware's Avatar
    April 27th, 2017, 01:46 PM
    Lack of activity on the PROM pins 1 and 2 doesn't necessarily mean that the PROM is bad, it may just mean that the exact combinations of states...
    56 replies | 1811 view(s)
  • SiriusHardware's Avatar
    April 26th, 2017, 11:05 AM
    Well done on the fault finding so far. That PROM (IC47) looks like it's programmed to be a custom address decoder, to select various ICs or banks...
    56 replies | 1811 view(s)
  • SiriusHardware's Avatar
    April 25th, 2017, 01:30 PM
    I'm surprised you haven't had more interest in this problem. I don't know the system as I never had one (couldn't afford one) but examination of...
    56 replies | 1811 view(s)
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