PET 4016 to 4096 Project (+64K RAM)

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PET 4016 to 4096 Project (+64K RAM)	by Bill Degnan - 10/25/2009 00:19
I finally got around to attempting to install a CBM PET 4032 mother board in my 4016 PET. The Commodore PET 4016-12 Computer. The 4016 motherboard can be upgraded with the 4032 (32K RAM version) in a matter of minutes. Aside from doubling the RAM (16K --> 32K) the boards are exactly the same, and so is the power supply. Why go through the effort of getting a paltry 32 more K out of the system? My ultimate goal is to turn my 4016 into a "PET 4096" and only the 4032 is compatible with the 64K memory expansion board. I don't have a 4032 anyway, and it's easier to change the "1" to a "9" on the case if I was to somehow change the front label. Here is a link to the PET 4032 mother board. Note the top line of RAM chips and then compare with this closeup of the PET 4016 mother board RAM. That's how you can tell the two apart. The 4032 board did not work. A non-socketed chip or component of the 4032 board is bad, and the board returns a garbled screen. Commodore 4032 motherboard problem. With the 4032 board still in the 4016 chassis; I swapped the socketed chips including the CPU (6502) and the ROMS, of the 4016 motherboard with the 4032 equivalent. Nothing easy was found to be bad. I put the 4016 board back into the system for now. Some day I will try again, this time in more depth; things like checking voltages of the non-socketed chips. Or just find a 4032 board. Commodore PET 4016 Boot Screen. More Pictures of Commodore PET 4016 Reply
Next Steps PET 4032 Board Repair	by Bill Degnan - 10/29/2009 08:39
I think first however I will check the voltages to all of the chips and components vs. the schematic. There may be an obvious short that I can detect. It may not be RAM because I recall from experience that on an older PET with socketed RAM we could still boot a computer with some bad RAM in any position except the first few slots, the system simply reports less memory. So, I will id which are the RAM that hold the ROMS and the bottom of memory (0000-1000) and replace them first. I don't think it's video RAM, what I believe we're seeing on the screen in the pic is what appears when you first power on a PET, but is then quickly replaced when the system loads BASIC into memory IIRC. Maybe someone else can confirm this. I also remember that on some PET boards (the 2001-8's) the order of the RAM is different, some of them start from the upper left to lower right, some the exact opposite. My hunch is that the RAM in the first slot is the first RAM in the line, etc. So, I am not going to start in the middle of the board. I think I would only do that if the system was acting flaky, or dying after a few minutes. That's the kind of environmental evidence that would indicate a mid board problem, all easy stuff already checked. Reply
PETVet	by Bill Degnan - 01/22/2013 10:43
PETVet http://www.bitfixer.com/bf/petvet Bought one of these devices and used to bypass RAM and ROMS on the 4032 motherboard and successfully boot. This tells me indirectly that there is a bad ROM most likely, or bad RAM. Or both. To upgrade a 4016 motherboard to a 4032; Jumper Z = 32K, Jumper Y = 16K. You can install 4116 RAMs in the empty spaces on the 4016 motherboard. Reply