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  • dave_m's Avatar
    August 8th, 2020, 02:20 PM
    dave_m replied to a thread Pet 8032 Keyboard mapping in Commodore
    Here is a page with a lot of information on keyboards and creating special EDIT ROMs for them. I'm not sure if this will do exactly what you want....
    2 replies | 95 view(s)
  • dave_m's Avatar
    August 5th, 2020, 09:11 AM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    Yes you can.
    84 replies | 1783 view(s)
  • dave_m's Avatar
    August 5th, 2020, 09:09 AM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    I wanted to make sure that PETTEST runs with those chips in place to make sure they were not shorting an address or data line, but I forgot you have...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    August 5th, 2020, 08:42 AM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    I wouldn't worry about RAM above $0800 right now. That can be fixed later. The system doesn't need to much RAM to boot.
    84 replies | 1783 view(s)
  • dave_m's Avatar
    August 5th, 2020, 08:34 AM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    Yes, with PETTEST installed, all seems fine. If PETTEST passes with all PIAs and the VIA installed, then we could go to the NOP address tester, but...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    August 4th, 2020, 10:12 PM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    My PET has much less ripple. See my message # 35.
    84 replies | 1783 view(s)
  • dave_m's Avatar
    August 4th, 2020, 09:54 PM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    The OP has the original PET 2001 with the 6540 ROMs and 6550 RAMs. 320008-sheets 2 and 3 and 320130-1...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    August 3rd, 2020, 01:59 PM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    As Dwight said in his message, 50 Hz would indicate a bad rectifier and a large 100 Hz ripple may indicate a failing filter cap. My reading at that...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    August 3rd, 2020, 11:39 AM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    After a little searching, I get to instruct Dwight on the operation of a Simpson VOM! (Blushing with pride) :p Here is a blurb from the manual: ...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    August 2nd, 2020, 09:10 AM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    His Dwight, Excellent tutorial. I forgot that simple voltmeters only rectify AC signals to drive the meter movement. On my VOM there is an 'Out'...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 31st, 2020, 03:28 PM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    Hi Dwight, Nice to hear from you on the 'The Commodore Channel'. I see your postings on the other forums. My 3 mV AC reading of the Vcc bus seems...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 31st, 2020, 09:30 AM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    Using a digital DVM, with the black probe clipped on the big cap C1 (23K uF) negative (blk wire) and the red probe in J8- pin 2, I get 0.125 VAC and...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 30th, 2020, 12:16 PM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    I checked the numbers and the correct sum for BASIC 1 for the $F000-FFFF range seems to be 0CA4 so your ROMs are correct, and the manual must be in...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 30th, 2020, 10:47 AM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    Oh! I thought you had compared with the manual. So I'm guessing the 0CD4 in the manual is correct and you may have a bad ROM (one of the 2K F0 or F8...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 29th, 2020, 12:37 PM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    You are correct. The two checksums from sockets H4 and H7 will add up to the 4K checksum for the $F000-FFFF address range and will equal $0CA4. Sorry...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 29th, 2020, 08:36 AM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    You are under no obligation in this forum to quote the price you paid although I would have told him $50 at a flea market and it would have made him...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 28th, 2020, 01:38 PM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    That should be a good place. Make sure the contact is good. All the old PET sockets are are notorious for being intermittent.
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 28th, 2020, 01:34 PM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    Good info, yes ROM at $B000 is empty. Key board is controlled by PIA #1 at G8. Is it in place or removed during this test? Yes it passed up to...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 28th, 2020, 08:45 AM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    This is indicating .75V of noise. This seems way to much for TTL if it is real. Where was your scope return for these measurements? A suggestion -...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 27th, 2020, 09:44 AM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    Eventually you may want the real BASIC 2 (zimmer BASIC3) as it fixes the IEEE port and allows for floppy drives or emulated PET Drives so you can...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 26th, 2020, 04:32 PM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    I think the set you have in your PET now is the BASIC 1 Revised (what zimmer calls BASIC 2). I did not realize the dash numbers on the 6540 ROMs do...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 26th, 2020, 03:56 PM
    No, sorry, I only found the link.
    10 replies | 2085 view(s)
  • dave_m's Avatar
    July 24th, 2020, 01:20 PM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    If it turns out you have a bad mix of ROMs and/or have to replace a bunch of them, consider replacing all of them using The ROMulator. For your...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 24th, 2020, 12:27 PM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    These should be the part numbers and dash numbers for the 6540 ROMs. The parts themselves may just have the dash number such as MPS 6540-013 the rest...
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 24th, 2020, 08:25 AM
    dave_m replied to a thread PETunia's Repair Log in Commodore
    My reading of the schematic indicates the following: C000 H1 901439-13 C800 H5 901439-14 D000 H2 901439-15 D800 H6 901439-16
    84 replies | 1783 view(s)
  • dave_m's Avatar
    July 20th, 2020, 10:02 AM
    Hutch, You did a great job on the video. I wasn't that interested in the project until seeing your video. Now I want one. Tynemouth did a great job...
    12 replies | 942 view(s)
  • luvit's Avatar
    July 19th, 2020, 11:35 AM
    Over for over a decade i've had lightning strikes damage equipment with buried cat5, and I've gone through two damaged fiber optic cables that was in...
    2 replies | 201 view(s)
  • dave_m's Avatar
    July 17th, 2020, 08:22 AM
    SkyCaptain, What happened with the EPROM programming? We could send you a programmed 2532.
    110 replies | 5940 view(s)
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About dave_m

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About dave_m
Biography:
Engineer for North American Aviation and its successors Rockwell and Boeing
Location:
Southern California, USA
Interests:
old computers and test equipment, American Civil War, tennis
Occupation:
Electronics Engineer

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