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  • daver2's Avatar
    Yesterday, 11:04 AM
    That’s one of the references I was trying to find. I suspect the voltage will fall not rise if the capacitor fails open circuit though. Dave
    223 replies | 15418 view(s)
  • daver2's Avatar
    Yesterday, 07:05 AM
    Tom, My guess about the isolated transformer secondary and capacitor would be a harmonic filter of some description. If the capacitor goes...
    223 replies | 15418 view(s)
  • daver2's Avatar
    February 28th, 2021, 02:19 PM
    No, I haven’t tried this procedure before. I am just thinking out of the box :-)! It is good that you are seeing some coupling though. I do...
    74 replies | 4784 view(s)
  • daver2's Avatar
    February 28th, 2021, 02:34 AM
    Yes, address $0000 looks fine. However, the interesting thing would be address $0001 (as stated back in post #164). The fact that the machine...
    177 replies | 6664 view(s)
  • daver2's Avatar
    February 25th, 2021, 07:56 AM
    daver2 replied to a thread Cbm 8050 dual drive in Commodore
    Hello again Ilpaninaro. When you say "works fine" do you mean it powers up and the green light comes on only? This is an indication that the...
    3 replies | 99 view(s)
  • daver2's Avatar
    February 24th, 2021, 02:01 AM
    daver2 replied to a thread Hi, I am Dalmas. in Introductions
    I have been able to find the schematics for the SIM4-01 and -02 but not the -03. If they don't exist online, could I ask that you preserve them...
    11 replies | 217 view(s)
  • daver2's Avatar
    February 24th, 2021, 12:22 AM
    Welcome. We are a global mix of both hardware and software. Plenty of people here that would welcome a new member! I am a member of a...
    3 replies | 125 view(s)
  • daver2's Avatar
    February 24th, 2021, 12:12 AM
    daver2 replied to a thread Hi, I am Dalmas. in Introductions
    Welcome to VCFED... Nice little card you have there. Let me get back to you presently about how much of a SIM4-03 you can test without a...
    11 replies | 217 view(s)
  • daver2's Avatar
    February 23rd, 2021, 11:09 AM
    daver2 replied to a thread PET 2001 Cover? in Commodore
    There may be a small market for these types of covers of course... Dave
    3 replies | 89 view(s)
  • daver2's Avatar
    February 21st, 2021, 08:07 AM
    daver2 replied to a thread Tek 405x web-browser emulator in Other
    Thanks Jos, I will add some of my microcode logic diagnostic code to the specific addresses around where it is playing with these locations to see...
    264 replies | 31508 view(s)
  • daver2's Avatar
    February 21st, 2021, 07:07 AM
    daver2 replied to a thread Tek 405x web-browser emulator in Other
    I think (:-)) I have put all of the infrastructure back in for interrupts now... I had to remove all of my diagnostic code within the I/O reads...
    264 replies | 31508 view(s)
  • daver2's Avatar
    February 21st, 2021, 06:26 AM
    daver2 replied to a thread Tek 405x web-browser emulator in Other
    It looks like the write to ROM from the microcode is intentional (unless I have misunderstood the I/D logic somewhere - which wouldn't surprise me of...
    264 replies | 31508 view(s)
  • daver2's Avatar
    February 21st, 2021, 03:54 AM
    The timing should be locked to a clock pulse (one of the 8 phases) and not left to the whim of a gate delay or pull-down capability. At that...
    177 replies | 6664 view(s)
  • daver2's Avatar
    February 21st, 2021, 02:27 AM
    daver2 replied to a thread Tek 405x web-browser emulator in Other
    Hi Monty, Yep, I have that document. This is a listing of the microcode not the firmware itself. It passes the 4052/4054 determination OK...
    264 replies | 31508 view(s)
  • daver2's Avatar
    February 21st, 2021, 01:26 AM
    >>> I know Dave doesn't like swapping stuff randomly, but It worked, so I would take it! Good to see that it passes my PETTESTER code (that...
    177 replies | 6664 view(s)
  • daver2's Avatar
    February 20th, 2021, 04:24 PM
    daver2 replied to a thread Tek 405x web-browser emulator in Other
    Hi Monty, Yes and no... I keep having a go. I get a bit further and then hit a problem and get distracted by real paying work! I then go...
    264 replies | 31508 view(s)
  • daver2's Avatar
    February 20th, 2021, 05:57 AM
    yep, classic short circuit tantalum capacitor across the power rails by the looks of it. Once it has gone short circuit, it takes the voltage down...
    15 replies | 403 view(s)
  • daver2's Avatar
    February 19th, 2021, 01:20 PM
    Chuck, That’s a nice description and avoids the ‘lazy write’ issue. Dave
    46 replies | 752 view(s)
  • daver2's Avatar
    February 19th, 2021, 11:04 AM
    daver2 replied to a thread PDP11 GUI Crash in DEC
    I am guessing that a new build of PDP11 GUI is going to be required. Either because Microsoft have 'retired' a function or that the parameters have...
    6 replies | 295 view(s)
  • daver2's Avatar
    February 19th, 2021, 02:31 AM
    You need about 10 posts... From the trace back in post #123 I think we concluded that address $0000 was OK and things started to fail at address...
    177 replies | 6664 view(s)
  • daver2's Avatar
    February 18th, 2021, 01:16 PM
    Sorry guys, I got sidetracked with real work today. I had a quick look this morning, and then the problems started that demanded my attention. I...
    177 replies | 6664 view(s)
  • daver2's Avatar
    February 18th, 2021, 05:51 AM
    daver2 replied to a thread PETunia's Repair Log in Commodore
    There is a schematic around - but it may be in one of the other Zimmers directories - and the transformer fitted may be different to the schematic...
    173 replies | 10860 view(s)
  • daver2's Avatar
    February 17th, 2021, 01:58 PM
    daver2 replied to a thread Partial Altair Kit I Bought in S-100
    That sounds like the logical approach! Buy what you really want to keep that interests you when it appears for 'sensible money' - and sell off...
    11 replies | 394 view(s)
  • daver2's Avatar
    February 17th, 2021, 12:46 PM
    daver2 replied to a thread Partial Altair Kit I Bought in S-100
    And I thought you said your collection was large enough now? Does that mean you are going to start selling things off and replacing them with...
    11 replies | 394 view(s)
  • daver2's Avatar
    February 17th, 2021, 05:49 AM
    Yes, weird... >>> I lose track... which memory location is currently being tested? That's why I am interested on the previous WRITE cycle. ...
    177 replies | 6664 view(s)
  • daver2's Avatar
    February 17th, 2021, 02:10 AM
    Mike, good thinking about the difference between the BDOS and COLD loader... Dave
    46 replies | 752 view(s)
  • daver2's Avatar
    February 17th, 2021, 02:01 AM
    Hi Greg, Thanks for the update. FA0 (for the refresh) is generated from RA7 (sourced from schematic sheet 8) and is a lower frequency than...
    177 replies | 6664 view(s)
  • daver2's Avatar
    February 16th, 2021, 02:20 PM
    Mike, There are two (2) ways of achieving the same result: physical and logical. If the physical arrangement of sectors is 1,2,3,4,... on the...
    46 replies | 752 view(s)
  • daver2's Avatar
    February 16th, 2021, 12:07 PM
    SECTRAN is a BIOS entry point to permit CP/M 2 to perform software sector translation (as has been stated above). If you are going to implement...
    46 replies | 752 view(s)
  • daver2's Avatar
    February 14th, 2021, 03:35 PM
    The first thing is to use your eyes and nose and look / smell for the dead components... We can take it from there... My guess would be a RIFA...
    15 replies | 403 view(s)
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