Odd datasette issue with Commodore PET

[bluejay]

My Commodore PET, upon closer inspection, had a bunch of issues that seriously affected functionality. For one, the entire right half of the keyboard was completely nonfunctional, and the cassette interface is partially broken.

 

The first issue was fixed by creating a few solder bridges over a thin crack across the keyboard PCB; along the way I had to disconnect the shift lock key cables and couldn't solder them back; my dad got rid of my conventional soldering iron when I got the hot air rework station. Anyhow, it's fixed and the keyboard is working fine now other than that shift lock key.

 

The second problem, however, hasn't been resolved. So, the datasette drive is functional, I use it all the time on my VIC-20. When I hook it up to the PET, it seems normal; playing, fast forwarding, and rewinding all work perfectly fine. However, when I actually try to load or save, it seems like the computer is getting no response from the datasette drive. No LOADING or SAVING or anything; the computer just stays at PRESS PLAY(&RECORD) ON TAPE #2 until I press the RUN/STOP key. The SAVE LED on the datasette does light up when I attempt to save a program, but when I play the tape on a standard tape deck it hasn't recorded anything.

 

I tried cleaning the contacts on both the datasette and the PET's cassette connector, and yes, I'm using the second cassette port and LOAD/SAVE"*",2. Should I try cleaning the contacts more thoroughly or might there be an issue with some kind of integrated circuit inside? The PET I have is a 4016-N; an early model with a 9" display and no built in speaker.

 

P.S. Damned commodore punched holes through 4 of the 8 blank RAM sockets; I should still be able to upgrade the thing to 32k using some extra wires right?

[carlsson]

Are your VIA and PIAs verified OK? The fact that half the keyboard + tape didn't work at first made me think of a chip failure but if you fixed the keyboard by soldering perhaps that was not the issue.

 

Can you use port #1 or did I miss something? It sounds like the motor or sense doesn't work if nothing happens when you issue a command. Yet if it winds freely it must get the power.

 

I don't know how much work it is to upgrade it by adding wiring, or if there is a different solution beyond the universal 6502 RAM/ROM board. It was recently mentioned in one of the FB groups. I'm afraid that for once Commodore did a good job when they drilled holes to cut off the tracks but with enough wire in the right places maybe it can be repaired.

[bluejay]

I haven't verified functionality on any ICs because of the fact that there is no even remotely easy way for me to do so. I only one of them are socketed that I can't identify without taking out the motherboard which I will tomorrow.

Tape port #1 is partially obstructed by a huge capacitor, at least, I think it's a capacitor. It's zip tied in place and prevents me from plugging in a datasette. I'll test it when I take the motherboard out.

I mean, to be awfully honest I think the RAM upgrade is going to be a complete pain in the ass. But looking at what's left of the traces I now have a general idea where stuff is supposed to go, and I can probably find a schematic somewhere to make sure I'm not going to be zapping anything.

I'll be back after a good night's sleep.

[bluejay]

I took out the motherboard, and I can confirm that tape#1 has the same issue. It's getting power but won't load/save. How exactly do I test the VIA and PIAs? Is the only way to take them out and put them inside another computer?

The lone socketed IC turned out to be the 6502.

There are 2 empty sockets on the motherboard; I assume they were for optional ROMs?

Upon closer inspection there are two capacitors next to each RAM chip, and empty holes for them next to the blank slots. I assume I'll have to install those as well.

I also discovered it's a REV E motherboard. I assume this PET's a slightly later version, made in the early 80s. Slightly disappointing, I kinda wanted a 70s computer.

 

Hold on, I am ridiculously stupid. I thought the tape port on the back was #2 and the internal one was #1. I tried LOAD and SAVE with the datasette connected to the external port and it worked perfectly.

Edited December 30, 2020 by bluejay

[bluejay]

I'm faced with yet another problem now, using wavprg. I tried using it when I first got my VIC-20 a while ago, back when, you know, I was using a portable DVD player for a monitor and had no floppy drive. I had no luck with it.

Wavprg has no setting for a PET, and a tutorial I found on the web suggests that I should use the VIC20 PAL setting and slow output. It only showed how to convert PRG to TAP, and I wanted WAV, so I inverted the waveform, set the frequency at 44100hz, volume at 254. Recorded it to a tape, and although the PET found the file the name was a random 4 character garble(different every time I tried to load), and it said "?LOAD ERROR".

Next I tried VIC-20 NTSC, frequency at 96000hz(as advised by someone on an old lemon64 thread), inverted waveform, volume 254, slow. This time it didn't detect a file at all.

What's the correct settings I need to use for it to work?

P.S. Having to record the wav to tape every time I want to test the wav file is tedious. Car cassette adapters should work right?

[bluejay]

Update: essentially have given up on working with the tape drive. I'll try a few more things but I'm sick of dealing with tapes now.

Meanwhile, I managed to get a $150 partial refund for a broken keyboard. Seems a bit excessive to me as well but oh well, that's what the seller suggested. I don't want an SD2PET because there exists cheaper alternatives. I'll see what becomes of cbmSD-mini and PETdisk and get one or the other.

Regarding the 32k RAM expansion, it's seems much more wise to get a PETvet than attempt to do what I planned on doing. However, bitfixer doesn't seem to carry them anymore, and Tynemouth Software is closed due to Covid-19. I tried contacting bitfixer about it. We'll see how it goes.

[bluejay]

Update #2: I have excellent news. Bitfixer has now finished development of PETdisk2.0(now called PETdisk MAX according to him) and will be ready for sale very soon. Apparently it comes with a wifi module and can function as a network drive, all at a cheaper cost than the original PETdisk!

Also, it turns out the Romulator is the successor to the PetVet, that has all the same functionality except it's better. It's still in stock available for sale.

 

Now all my problems have been resolved, I have the perfect PET. Also, did I mention that I like PETs with 9" displays more than 12" ones? I used to like the latter because the length of the monitor matched the main case, but having used the 9" one I think the smaller display makes the video look much sharper and generally looks more adorable than the 12" one.

 

Okay, I'm just ranting at this point, I'm so excited!