Recent content by Hutch

I always assumed the use case for the IBM 3740 compatibility was as a "key punch" to write code or input data that would eventually be passed to the mainframe for processing. I seems that a SuperPET, with it's serial interface connected to an IBM would make it more useful, though the primary use...

OK. I found a pattern. Bit 0 is alternating between 0 and 1 every other address. I don't think I've seen that mode before. Bit 1 is stuck on always and Bit 2 is sometimes on when it should be off and off when it should be on. I'm assuming the test is repeating and sometimes reading back...

I'm working on an 8032 with bad system ram in both lower and upper banks. Pettester v4 is passing the video ram test and and moving on to 0/1 page. I know the lower bank is bad but I'm trying to figure out which bits/chips are bad, so I don't have to desolder all eight of them. I'm reading now...

The Prototype was wooden with curved styling and a cassette drive. I've never seen that one before, it looks like someone's project. The PCB is from a '79 2001-N and I see what looks like a VIC-20 8K RAM cartridge. The voltage regulators are removed and it looks like a custom power supply...

AFAIK, the 6510 isn't drop-in compatible with the 8501. There are a couple of 8501 replacements being made. This one is FPGA, and he only makes a batch occasionally since they are not in high demand. https://www.sellmyretro.com/offer/details/30475 Another uses a 6502 with an add-on daughter...

Booting to the MLM means the CPU is running into a BRK instruction (00) when it shouldn't. This is normally cause by a bad ROM. NOROM might be OK, and the onboard ROMs fine, but IF the SuperPET ROMs are also on the bus and being selected, that will interfere with the PET ROMs in the same...

The Character ROM is not connected to the CPU Bus so no need to worry about the NOROM signal for the Character ROM. It remains in use no matter which mode you're in. There's no way it could cause either mode to stop working. My earlier mention of the SuperPET RAM and 6551 ACIA is because some...

There's a lot going on with the Super PET. I'm assuming you have the two board system, just the 8032 main board and one SuperPet board? Is the 8032 originally from a SuperPET? There's a mod that's required to send the system clock up the ribbon cable to the 6809. Sounds like it's crashing...

It's tricky to find the right tube that's compatible electrically and mechanically for mounting. FWIW, There has been one success sourcing replacement parts from an old Zenith TV. This was for an older Chicklet PET with the white phosphor screen though. Link...

Ahh, yes. I see, that logic is only there for the read/write signal.

In theory, the MUX should only switch to the CPU address lines when the CPU is actually addressing video RAM. There's some logic with BA11 and SEL8. Unless a program is constantly writing to vRAM, it should only be selected around 60 time a second during the interrupt cycle. But the video...

I haven't seen that one before, but it looks like an upper bit in the video address counter is failed and it's wrapping around to the start of video ram. Hard to count the spaces from the photo. Video RAM is 1024 bytes on a 40 column PET which is 10 bits 1111111111 If the high bit was stuck...

I've seen this before. In my case the vSync was at 1MHz due to a floating output from a 74LS08 AND gate at C6 (on my 2001-8) On the 2001N/30xx it might be the LS74 at G8. A floating output from the LS08 AND gate pin 3, would cause that flip-flop to toggle at the clock rate. Could also be the...

Possible the PCB is slightly warped? 200 ohms should be fine. Have you tried a mild abrasive to remove the hardened rubber surface and make the pads more flexible? There are some chemical rejuvenation methods too <https://youtu.be/n9gGz2n-sBU/>

Commodore didn't include any serial communications with the PET. Unlike the VIC-20 and C64, device #2 on the PET is a second cassette interface. There was a modem sold that connected via the IEEE 488 port, but no RS232 or serial device. There have been a few programs created that use the same...