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  • daver2's Avatar
    Yesterday, 10:34 PM
    daver2 replied to a thread Mark-8 Clone Project Begins in Other
    Nice look! Dave
    74 replies | 6948 view(s)
  • daver2's Avatar
    September 17th, 2018, 11:15 AM
    More PETs... The more the merrier... Welcome to VCFED. Dave
    223 replies | 9070 view(s)
  • daver2's Avatar
    September 15th, 2018, 11:51 AM
    If you have a 'kettle' lead on your PET - it probably contains an RFI filter - and this is possibly the culprit. Dave
    11 replies | 218 view(s)
  • daver2's Avatar
    September 15th, 2018, 09:19 AM
    daver2 replied to a thread Bigboard II in Other
    The cable you identified is/was designed for an IBM PC parallel (Centronics) port. I don't think there was a specific cable. I think what you will...
    16 replies | 416 view(s)
  • daver2's Avatar
    September 15th, 2018, 08:08 AM
    daver2 replied to a thread Bigboard II in Other
    Falter, Note that what you have referenced on ebay is a 26 way IDC to 25 way D adaptor. 25 pins of the IDC connector will be wired to the 25 ways...
    16 replies | 416 view(s)
  • daver2's Avatar
    September 14th, 2018, 10:12 AM
    Yes, the first test (before anything else) is to disconnect both the monitor and the PET main board from the power supply itself (just leaving the...
    11 replies | 218 view(s)
  • daver2's Avatar
    September 10th, 2018, 11:11 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    It is still not working - but it is not working for potentially the right reason now - if that makes sense?! I think I now need to 'fix' the...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 10th, 2018, 11:01 AM
    daver2 replied to a thread Sketchy auction in Rants
    If I am interested in an item - I put my maximum bid on it and that is that. No messing about. If some other people want to play games with bids -...
    6 replies | 188 view(s)
  • daver2's Avatar
    September 10th, 2018, 10:27 AM
    If you can dig that up I would make an Altair clone just to demo it! Dave
    6 replies | 195 view(s)
  • daver2's Avatar
    September 10th, 2018, 09:33 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Downloading now Al... dave_m: the two devices used in the pipeline are 273 and 374 - both of these are low->high latch. Dave
    34 replies | 703 view(s)
  • daver2's Avatar
    September 10th, 2018, 04:31 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Yep, you're right! a 373 is the transparent version and the 374 is the high-going edge triggered version. I think the problem was it was late at...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 9th, 2018, 10:33 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Still not working - but I have just had a thought (something along the lines of a pipeline issue). What if the flag register changed on every rising...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 9th, 2018, 08:59 AM
    daver2 replied to a thread Bigboard II in Other
    I don't think (from what I've read) you will get a prompt until the monitor sees a <CR> from the parallel keyboard or one of the serial ports. ...
    16 replies | 416 view(s)
  • daver2's Avatar
    September 9th, 2018, 08:24 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    It's a '374 according to the schematic. Latch / flip-flop - the TI data sheet appears to use them interchangeably. The key thing is that the...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 9th, 2018, 07:34 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Many thanks Monty for the help you have given. So, not done a full check of the microcode ROMs - but a very 'quick and dirty' sample check of...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 9th, 2018, 04:37 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Thanks Monty - you are a star! I have downloaded your files and will have a look through them shortly - although I see the addresses are doing...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 8th, 2018, 11:23 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    We only really need one (good) set of traces and, even then, we don't actually need the traces themselves. The URAx bits form an address (lets say a...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 8th, 2018, 02:44 AM
    daver2 replied to a thread Bigboard II in Other
    You should just need +5V for the logic and +/-12V for the RS232 buffers. The unit contains an EPROM programmer. The programming voltage is...
    16 replies | 416 view(s)
  • daver2's Avatar
    September 7th, 2018, 11:14 PM
    daver2 replied to a thread Bigboard II in Other
    I saw a couple of these on e-bay, but decided not to go for them in the end. I did lookup the schematics though, so give me a short while to do a...
    16 replies | 416 view(s)
  • daver2's Avatar
    September 7th, 2018, 01:43 PM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    So, I have been looking a bit further at the microcode and found a few anomalies. The microcode instruction at address 0x03A ends up jumping to...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 7th, 2018, 09:32 AM
    Yeah, Hi guys. Read what it says, not what you think it says... Been there, done that, got the tee shirt :-)! Dave
    25 replies | 402 view(s)
  • daver2's Avatar
    September 7th, 2018, 12:30 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Yes, URA0 through URA9. I don't think URA10 is used (it was reserved for larger microcode ROMs as a later enhancement). If J207 3-4 is made then...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 6th, 2018, 01:49 PM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Everything I have looked at tonight in the emulator looks good. Still doesn't work yet though... I still can't see how it can work if it is...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 6th, 2018, 12:45 PM
    Many years ago I came across IC sockets that had been 'life expired' in the factory by firmware changes before releasing the items to us. We had some...
    24 replies | 621 view(s)
  • daver2's Avatar
    September 6th, 2018, 06:59 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Just been looking at the schematics again. J203 and J204 of the ALU board carry the microcode address to the microcode ROMs. It may be useful to...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 6th, 2018, 04:42 AM
    Nice work dave_m. Yes, some systems fight you all the way... Yes, some sellers are trying to get way too much money for the PETs they think are...
    24 replies | 621 view(s)
  • daver2's Avatar
    September 6th, 2018, 04:37 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Had a thought over lunch... ROMs U170 and U172 decode the CCC microcode bits and define whether byte or word status bits are being monitored. I...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 6th, 2018, 03:03 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    At this point we are not even running code out of ROM. On start-up the microcode machine tests out the ALU circuitry itself to see if it is...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 5th, 2018, 02:03 PM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    I have just re-checked my logic and come to the same conclusions as previously. Microinstruction 36 does something with the registers and...
    34 replies | 703 view(s)
  • daver2's Avatar
    September 5th, 2018, 11:12 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    So, After downloading various VHDL and VERILOG implementations of the AM2901 bitslice processor - and finding all of the implementations different...
    34 replies | 703 view(s)
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    http://www.vintage-computer.com/vcfo...ad.php?t=12058

    EPROM's don't last forever, and eventially you have to reburn them which I think is why your Tektronix isn't working. Have you tried contacting the guy to that website to see if he can reburn your EPROM's for you? Or if you have a EPROM burner, have you asked him to email you an image copy?
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