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  1. dave_m

    Another PET 2001 with no cursor...

    Hi Philip, Nice to hear from you. I'm impressed you have keep that old Pet working for so long. I remember when you, MikeS and I (plus others) fixed that PET so many many years ago. You took many great scope photos that really helped us find the usual problem (flaky NAND gate?). Looks like you...
  2. dave_m

    Another 8032 to fix!

    Good work daver2 and KevinO...
  3. dave_m

    CBM 8032 won't boot

    Daver, no, as Hugo says, it is a BRK (B*) to the Monitor. If /diag was held Low, it would perform a Call to the Monitor. The Program Counter is sometimes in low RAM and sometimes at $Dxxx.I would guess bad ROM or bad zero page RAM.
  4. dave_m

    New Release: PETSTRIP for PET/CBM 3032 and 4032

    It is amazing what can be done on a 45 year old first generation home computer by creative people.
  5. dave_m

    Converting CBM 8032 PET to switching power supplies

    Yes, the video board by the PET can pass the 21VDC through its full wave rectifier with minor voltage drop and drive the the voltage regulator chip which outputs the required +18VDC. See Video board schematic http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/8032/321448.gif
  6. dave_m

    Commodore PET 2001-8 Question

    That top ROM is stamped 6540-014 and is from a BASIC 1 set and the chip goes into socket H6. Here is the info on that part: H6 901439-06 6540-014 ROM Basic 1 D800-DFFF And note that there are no way to know that this 45 year old part is still working unless it was recently tested.
  7. dave_m

    PET 4032 - can't run d64 images from PETdisk MAX v2

    Yes, the pass thru IEEE port connector is a handy feature.
  8. dave_m

    PET 4032 - can't run d64 images from PETdisk MAX v2

    Whenever I have to do a firmware update on a gadget, I break a sweat thinking of all that can go wrong leaving me in the Twilight Zone.
  9. dave_m

    PET 4032 - can't run d64 images from PETdisk MAX v2

    Perhaps the MAXv2 firmware has been corrupted. Did you try to reload it? It used to be somewhat difficult task requiring an Atmel programmer, but he has added code to do this within his gadget. Of course you may be wary of doing this since the .prg files are working right now, and if the boot...
  10. dave_m

    3032 - 2001N Repair

    If the signal Graphic is stable, then the VIA source is OK. It may be the character generator ROM itself. Can you replace it with a programmed 2816 EEPROM? You want to use the 2K bin file characters-2.901447-10.bin from this page...
  11. dave_m

    Commodore Pet 2001, to buy or not to buy?

    It may also not have the original RAM and ROM chip sets. You would have to look inside to see if it has a RAM/ROM replacement board plugged into the CPU socket. It would be fully functional with a replacement RAM/ROM board and maybe even more reliable, but not worth the top money to a collector...
  12. dave_m

    CBM 4040 5 Flash Failure! Need parts.

    The 6530 RRIOT chip part number for the 4040 drive is: 901466-04 (6530-34) - Shugart SA390 drives in 4040, DOS 2.2 Workarounds include using an old 6532 RIOT chip (still found) with an EPROM to duplicate the 1K ROM in the RRIOT. For design info, see these old designs that are no longer for...
  13. dave_m

    PET 4032 - can't run d64 images from PETdisk MAX v2

    From the max GitHub page. Note that there are no spaces in the command line. D64 The PETdisk MAX currently supports D64 files for both reading and writing. To mount a D64 file stored on either an SD card or network drive, use the following command: LOAD"$:filename.d64",devicenumber This will...
  14. dave_m

    PET 4032 - can't run d64 images from PETdisk MAX v2

    That command should not need the wedge. There is another command that uses the wedge. I’ll have to look it up. You are using the normal/graphic character set that is usually used for games.
  15. dave_m

    PET 4032 - can't run d64 images from PETdisk MAX v2

    You did not say what command you used. Did you mount the image using this command: load "$: petrobots-shareware v1.1.d64", 8 NOTE: do NOT use space after the colon. I had to show it with a space to avoid an unwanted smiley. Then list the directory to view the files.
  16. dave_m

    PET reset switch circuit with a condensator for pulling the diagnostics line down

    Mike, was that your "Soft Reset" for the PET from about 100 years ago? As I recall, it would somehow reset the PET but would keep the user program and variables intact? I wonder if these new circuits will also do that? I think so if the monitor is exited right away?
  17. dave_m

    Dead 2001

    daver, you are correct about the issue with 2516's not good replacements for 2316 ROMs in sockets H5, H6 and H7 due to pin 18 chip enable polarity (CS2). And yes the 2532 can be used with 4K images to replace BASIC 2 in either sockets H1, H2, and H4 for C, D and F ROMs or in sockets H5, H6, and...
  18. dave_m

    Less than 2 weeks to the Commodore Los Angeles Super Show 2023!

    Looking forward to photos!
  19. dave_m


    Hi Hugo, I was working at North American Rockwell (later Rockwell International) when we became the first second-source to MOS Technology on the 6502 family of parts. The R6520 was NMOS, and later the R65C21 was CMOS N-well silicon gate technology which was compatible with the NMOS parts (not...
  20. dave_m


    When ordering the Western Design Center part, make sure to specify the N-MOS compatible part 40-pin DIP as Nivag has listed. It has to do with drive capability I think.