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PET 3032 no video

T

TommyE

Member
Joined
Nov 19, 2020
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20
Location
Norway
Hello

Wondering if any of you out there with knowledge of the PET 3032 monitor knows if there is a way I can connect e.g. a Commodore 64 to the monitor to test the monitor.
I see from the schematics that there is H, V and Video signals on the internal cable.
Are there any prebuild adapter to buy?
I want to test my PET screen before doing any serious attempt on repairing the machine.

Regards
TommyE
 
If you absolutely want to test it with some other computer, a PC with a CGA card or the 80 col output of a C128 would likely be a better fit. Not sure if the sync polarity is correct or not.

I would recommend that you do things the other way around - I.E. if you want to work on the main PCB in your PET without involving the monitor, build one of the cheap simple composite adapters that connects to the user port (or for that sake connect to the monitor connector).

In general the video generation part that generates the sync pulses are relatively simple and I can't recall ever hearing of damaging a monitor due to faults in this circuit. Power up your PET without power to the monitor, and measure that you have reasonable sync signals, and then just connect the monitor. For all 9" PETs the sync generation is totally separate from the CPU, so as long as the oscillator is running correctly and the counters/dividers are working properly the sync signals should be correct.
 
Thanks for your reply.

I'm new to the PET stuff, but fairly into C64, VICs, Amiga and other stuff so I was hoping to get this newly aquired PET up and running.

I have verified the usual processor stuff, and clocks, busses look ok for now.

As I have no H V or Video signal, I have now disconnected the cables to the monitor, both power and videocable so I can focus on getting the mainboard up and running first.

I have traced back and have so far found that 1/2 of a JK flipflop is gone, no new ones in my drawer so I had to order some...

I assumed that the sync generation was separate from the CPU, but very good to get that verified :) Was about to ask that question actually.

Hoping to get some sync pulses going on the video connector so I can see the screen and eventually see if there are other things wrong..

Will see if I can build a converter so I can hook up a composite monitor. Saw a small circuit with '02 chip, I think it was, somewhere.
 
JK flip flop? Do you have the old original board with a part number like 320008?
A 3032 would have a part number similar to 320351. Can you post a picture of the main board?
Do you have a problem with no vertical drive (60 Hz)? The horizontal drive circuit is more straight forward. Do you have the 15.6 KHz signal of the horizontal drive?
 
dave_m said:
JK flip flop? Do you have the old original board with a part number like 320008?
A 3032 would have a part number similar to 320351. Can you post a picture of the main board?
Do you have a problem with no vertical drive (60 Hz)? The horizontal drive circuit is more straight forward. Do you have the 15.6 KHz signal of the horizontal drive?
Click to expand...
Hello

Well it says 2001-32N C on the back, and 3032 on the front of the machine.


Turning the mainboard over it says : partno 320350 rev E
The chip I've traced to, and tested bad 'till now is H6, a 74LS107

I have no horisontal or vertical signals at all.

Will continue when the 72LS107 arrives.

PET.jpg
 
That is a key flip flop. If the problem is the Q output on pin 3 (RA1) is not toggling then you will not see Horizontal or Vertical drive signals. I assume you are getting the 1 MHz clock on the clock input (pin 12)? After you replace H6, things should greatly improve. If you then get the ~15.6 KHz Horizontal signal and the 60 Hz Vertical signal you will be ready to connect your video board/monitor. Good troubleshooting so far!
 
dave_m said:
That is a key flip flop. If the problem is the Q output on pin 3 (RA1) is not toggling then you will not see Horizontal or Vertical drive signals. I assume you are getting the 1 MHz clock on the clock input (pin 12)? After you replace H6, things should greatly improve. If you then get the ~15.6 KHz Horizontal signal and the 60 Hz Vertical signal you will be ready to connect your video board/monitor. Good troubleshooting so far!
Click to expand...
Thanks for confirming that, my hopes now are high :) Cannot wait getting that chip in. I was even sitting here thinking if I could find a 74ls107 to borrow from some of my other stuff, but haven't found any...
 
On your board, the H and V drive signals are generated independently from and CPU activity. There is a description I wrote about how this works here:


Somebody in the past did post a test generator they made to check the VDU on its own.

However, a good move is to simply disconnect the VDU, until you are sure that the mobo is producing the two correct H & V drive signals. The V drive is not an issue no matter how disorganized it is. The H drive, on the other hand, can cause problems in some cases for the VDU if it is grossly abnormal in frequency or duty cycle.
 
Hugo Holden said:
On your board, the H and V drive signals are generated independently from and CPU activity. There is a description I wrote about how this works here:


Somebody in the past did post a test generator they made to check the VDU on its own.

However, a good move is to simply disconnect the VDU, until you are sure that the mobo is producing the two correct H & V drive signals. The V drive is not an issue no matter how disorganized it is. The H drive, on the other hand, can cause problems in some cases for the VDU if it is grossly abnormal in frequency or duty cycle.
Click to expand...
Wow, that was an extensive document. Will bring my ipad to bed today :)

I have alot to learn about the PET, abit different from eg. VIC and C64. Want this up and running so I can try PETSCII robots :)

Yes, agree with you, already disconnected the VDU, both power and signal. Also soldered in a reset button so I dont have to flick the switch on/off all the time.
 
TommyE said:
Wow, that was an extensive document.
Click to expand...
Yes, Hugo has done a great job creating this report. A bad IC on sheet 7 of the 2001N schematic can cause many hours of frustrating troubleshooting. Untold many people have given up trying to fix their machine over the years because of sheet 7. But now thanks to Hugo and his circuit analysis, most can succeed in the repair.

Later model PETs (4000 and 8000 series) replaced the sheet 7 circuitry with the Motorola 6845/MOS Technology 6545 CRT Controller to perform this function. A drawback here is that the CPU must be running properly in program to initialize the CRT Controller registers with the correct parameters and get the Vertical and Horizontal drive signals running.
 
Thank you all for valuable feedback to a complete PET newbie. Started on 0%, already learned a lot. Will come back with an update when my chips arrive.
 
Got my chips this morning, hooked up the scope, put a new 74LS107 in, turned on the PET, got pulsing sync signals, hooked up the monitor again, SUCCESS a nice picture. :)

I must be having an old BASIC no version number on the screen, so now to download and burn the latest versions.

Also, will need to swap out the white sockets as I need to wiggle the ROMS abit from time/time as there is bad connection there, but this is expected I guess after reading about these sockets.

Again, thanks for the pointers.

Regards
Tommy
 
Good work!
Take your time replacing the sockets so the board will not overheat, or you may lift some traces.pads.

If you program a new set of 2532 EPROMs, remember to cover the UV window with a label that indicates the ROM part number or location like D5, D6, etc. I also like to add the type of EPROM and, if there is room on the label, the checksum. This allows for easier reading of the the EPROM in a programmer to verify the contents. The Edit location (D8) can take a 2516, 2532, 2716, or a 2732 if the 2K code is put into the upper half of the 2732.
-dave_m
 
If you post a picture of the start-up screen you can identify which version of BASIC it is from the image.

Likewise, if you post the numbers on the ROMs, you can look them up to obtain the definitive version of BASIC.

EDIT: I see from a photograph you posted that the ROMs have been replaced with EPROMs (minus their labels to tell you what they are)!

Dave
 
There is an interesting thread over here: https://forum.vcfed.org/index.php?threads/c64-in-pet-s-case.1243681/. However, for your (and our) sanity, I would not recommend going this way :)!

The PET monitor is a bit unique; so driving it from most sources (other than the PET itself) is out of the question.

PS: Don't forget to download a copy of my PETTESTER and pop that in place of the EDIT ROM to checkout the functionality of the PET.

Dave
 
If you anyway are going to program new ROMs, maybe consider using adapters that allow larger ROMs and add a switch so you can select between all relevant ROM versions?

I'm not 100% sure but I think that some software only works with certain ROM version. That might had been the case only for the first and "all other" ROM versions though, and since the first version was only available for the 40 col initial 2001 my idea might not be that useful after all?
 
@dave_m Yes, those are very good remiders :) Sometimes I'm good at doing that. (Have a template and small stickers on sheet, ready to print), other times I just burn and forget, happy it works. Will make proper stickers on the ROMS this time as I'm not that into PET roms just yet.

@daver2 Yes, I saw that thread. I actually tried programming an Arduino to make those sync pulses to make a tester. I sort of got it working, at least so that I was fairly certain that the monitor would be OK. But then the chips came, and it all just started working. Also I found out by looking at the original chips that I had basic 2.0
It even had a Norwegian character ROM in it, so I can type the ØÆÅøæå letters, nice detail for me being a Norwegian.

@MiaM I do have some adapters. I will probably get familiar with all different ROM versions out there and see if I can make up a switcher at some point. I have a stack of small adapter boards for upto 27512. Fired up the old trusty DATA I/O programmer and burned a few 2532's for now :) Looks kind of original.

What I want to do now is to convert a 1541 to IEEE488, saw a mod that seemed doable. Only thing is that I would like to be able to switch between using it in IEC, C64 parallell mode and IEEE488 mode. So I will need to see how much I must change to make that possible. I might be that I just convert a drive and let it be IEEE488 only.

And I have also bought a real mini amplifier that I want to connect to CB2 and a little (maybe 2 small) laptop speakers I have from a Lenovo that I binned.

Another thing. I think I remember reading something about either PACMAN og SpaceInvaders a few years back with a custom graphics ROMS for the PET. I cannot find back to that, so I might be dreaming or if that was for another system... Do any of you know?
 
Sorry if I'm very much Captain Obvious here, but re the ROM version: It's a good idea to test them out in VICE before deciding to actually do anything with them. Also in addition to the character ROM there is also another ROM (not sure if it's the editor or kernal ROM) that handles the keyboard layout. (I.E. if you have the Norwegian letters on the correct places on the keyboard you also need a matching ROM for the keyboard layout).

I also had a look at the project to convert a 1541 to IEEE488. It seems like a cool project, especially making it switchable. However AFAIK there are very little software for PET that actually needs a real physical disk drive, and thus a modern emulator would likely be fine. (One of the few examples of software that needs a real disk drive, or at least emulation of a .d64 disk, is surprisingly Zork. Recently in a Swedish vintage computing Facebook someone discussed this, and someone made patches to make Zork run correctly using an 8050 disk drive :) ).
 
MiaM said:
Sorry if I'm very much Captain Obvious here, but re the ROM version: It's a good idea to test them out in VICE before deciding to actually do anything with them. Also in addition to the character ROM there is also another ROM (not sure if it's the editor or kernal ROM) that handles the keyboard layout. (I.E. if you have the Norwegian letters on the correct places on the keyboard you also need a matching ROM for the keyboard layout).

I also had a look at the project to convert a 1541 to IEEE488. It seems like a cool project, especially making it switchable. However AFAIK there are very little software for PET that actually needs a real physical disk drive, and thus a modern emulator would likely be fine. (One of the few examples of software that needs a real disk drive, or at least emulation of a .d64 disk, is surprisingly Zork. Recently in a Swedish vintage computing Facebook someone discussed this, and someone made patches to make Zork run correctly using an 8050 disk drive :) ).
Click to expand...
daver2 said:
It is the EDIT ROM.

Dave
Click to expand...
Hmm, cannot seem to find anything else than Swedish, German and English (of course) editor roms on zimmers.net, but these are for the 80 column PETs, maybe the 40columns don't have national versions?

It will probably be alot easier with a SD2PET, but hey... :) I'll see what time allows me to do.

@MiaM good tip on VICE.
 
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