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 portcommodore.com PET/CBM FAQ
 PET/CBM OPERATION AND TROUBLESHOOTING

HOW DO I LOAD A PROGRAM OFF OF A TAPE?

To load a program off of the tape, all you have to do is use the LOAD command. If you use just LOAD you will load the first program the PET finds on the tape deck plugged into port #1. You can specify a file to load by entering:

LOAD"FILENAME"

Where FILENAME is the name of the file. If you mistype the filename the PET will pass by the program if you type the first few characters of a file name you will get the first program that starts with those characters. To specify loading from tape #2, you would enter:

LOAD"FILENAME",2

If you want to load the first program from type 2 you need to still have the quotes, just don't put anything in them:

LOAD"",2

Most programs won't automatically start when loaded, once the program has finished loading enter:

RUN

to start the program. If you think the PET is done with the tape, make sure to press the stop button and rewind the tape (if necessary)

HOW DO I LOAD A PROGRAM FROM A DISK?

I have two great little texts that talk about loading programs from the disk drive, as well as the other necessities such as formatting disks, listing directories, etc.:

Disk Drive Loading Basics - listing disk contents, identifying programs, loading.

Disk Usage Basics - Using the disk drive (formatting disks, etc.)

HOW CAN I GET PET PROGRAMS FROM DISK TO TAPE?

You can just LOAD the program from tape and and SAVE them to disk one after another, of course, if you are using a VIC/64/128, etc. the loading address will get messed up. Fortunately there is a wonderful file copy utility available for PET (4.0), VIC (12k+), and Commodore 64/128, called 'Unicopy'.

Unicopy (written by the famous Commodore enthusiast, Jim Butterfield) allows you to copy from disk directly to tape. This of course preserves the loading address and makes things much easier. (also it performs multiple file copies instead of just one program at a time).

HOW CAN I GET PET TAPE PROGRAMS ONTO DISK?

Again you can do LOAD and SAVE as I mentioned or use a handy little utility I had discovered for the 64 (which I have listed in the PET/CBM Cross-Platform section.

WHERE CAN I GET SOFTWARE FOR MY PET?

Unfortunately PET software is not too easy to come by as it is for 64 and VIC-20 collectors (though originally it was mainly converted PET programs that first appeared for the VIC-20 and Commodore 64.)

I have listed some locations on the PET/CBM Resources section of the PET FAQ.

I HAVE A PET AND IT DOES NOT WORK, BEFORE I LOOK FOR A REPAIR SHOP IS THERE ANYTHING I CAN TRY MYSELF TO REVIVE IT?

PETS are pretty hardy beasties and usually don't die outright, there are times when all you need is just a little user intervention to get them running again.

First check the fuse, which should be next to the power switch on the back, this sometimes can be the culprit (and in the case of schools PETs, sometimes it is missing).

Second, open the case and re-seat the socketed chips. The PET computer chips have a tendency to creep loose of their sockets, you might try (with the PET's power off and you grounded) to first push down on each of the socketed chips (mind any pins sticking out, you don't want to bend them!) usually you will hear a sound of them sinking in a tad more. once done, try the power again.

If that doesn't work; you can pull each of the socketed chips and re-insert them, this has also been proven to work in some cases.

Well, if those don't work, then unless you are an electronics technician, it's off to the shop (also check with your local Commodore users group, they may have some electronic whiz members). Call around to local Computer and TV repair shops and see if they have a technician that can diagnose and repair older electronic equipment (some don't, they just swap circuit boards, which would not be available in this case.) Cross your fingers and hope it isn't some long out of production chips.

EVERYTHING SEEMS TO BE HOOKED UP OK BUT I CAN'T SEEM TO LOAD ANY PROGRAMS

One of the most common occurrences is that you placed your devices (tape, disk drive) to the left of your PET. The monitor on the PET is not as well shielded as modern monitors and puts out a lot of interference where the video flyback circuitry is. Try placing them to the right of the PET.

Other common TAPE problems:

Disk Problems:

    flashes:         4040                             8050
       #   cause:      location:            cause       location
       1  - Zero Page - 6532, C1, E1         Zero Page - 6532, C1, E1
       2  - ROM       - H1                   ROM       - 2364, L1
       3  - ROM       - L1                   ROM       - 2364, H1
       4  - ROM       - J1                   N/A
       5  - Zero Page - 6530, K3, 6504, H3   Zero Page - 6530, K3, 6504, H3
       6  - N/A                              N/A
       7  - RAM       - 2114, D4, D5         RAM       - 2114, D4, D5
       8  - RAM       - 2114, E4, E5         RAM       - 2114, E4, E5
       9  - RAM       - 2114, F4, F5         RAM       - 2114, F4, F5
      10  - ROM       - 6530, K3, 6504, H3   ROM       - 6530, K3, 6504, H3

I'M HAVING KEYBOARD PROBLEMS, WHAT CAN I DO?

There are two common keyboard problems on the PET, the most common is a dirty keyboard, that is where some or many keys are not working or don't work well. The second my be a loose wire on the keyboard cable, where every other, third or fourth key doesn't work. Both jobs require a little skill with a soldering iron and normal precautions to protect your computer from static. I am going to discuss just cleaning the keyboard; if you think you have a loose connection, you may consider going though this process as it will also give you easy access to the wires that may be broken, and let you do your repairs long the way.

Cleaning the keyboard:

Cleaning the PET's keyboard is not a hard process but a tedious one. Nor is my process a standard or fool-proof; everyone has their own idea on how to do this and I offer no guarantee that it will fix or not damage your computer, if you are uneasy with the steps presented, then you should strongly consider letting an experienced electronics person do the job for you. In order to clean the contacts you will need to remove the keyboard from the computer and partially disassemble it, then re-assemble and test, I have had to disassemble and reassemble stubborn keyboards up to three times to get all the keys working so don't be frustrated if it does not work on the first or second time.

Tools you will need:

 

  1. Open the PET cabinet.
    1. Under the white top of the PET cabinet, near the front on the left and right sides there may be two phillips type screws holding the cabinet shut, remove them.
    2. Lift the white top from the front, (*there is a hinge in the back), careful not to lift too far to stress the keyboard or video connections.)
    3. Locate the wire 'hood prop' (either in the front base or under the hood on the left side, undo from it's hook and place in (or next to) the screw cavity where the case screw was.
  2. Remove the keyboard assembly.
    1. carefully work the keyboard connector loose from the main circuit board (it's been a few years, don't force it too hard.)
    2. remove the large screws holding the keyboard assembly to the case and take the keyboard to your clean work area, be careful of bending the keyboard wires at the PCB, the older the PET the more brittle the connections may be.
  3. Disassemble the keyboard PCB from the keyboard mechanism.
    1. flip the keyboard upside down, you will see the PCB section of the keyboard, along the center there are two wires that are soldered to two pins, this is the shift-lock switch connection. (if you had a steel plate under your keyboard assembly there probably is a square of sticky foam covering those contacts) you will see about 20 or so tiny screws holding the PCB onto the assembly.
    2. With the soldering iron, undo the wires connecting to the shift-lock switch, do not linger on those contacts too long or use a high wattage iron, it could damage the plastic workings of the switch.
    3. With the small screwdriver remove all the tiny screws, make sure the driver has a snug fit, you don't want to strip the screwdriver holes.
    4. Remove the PCB from the keyboard assembly, note: On some boards, the 'little rubber cups' act as a contact and sometimes spring, don't loose track of those, put them back in the receptacles they came out of.
  4. Clean the PCB section.
    1. wipe the PCB section with the towel or cloth to remove any dust.
    2. with the eraser, 'erase' the 'gold fingers' of the key contacts, not too hard else you remove the traces.
    3. wipe the PCB to remove eraser crumbs.
    4. dampen a towel or cloth with the alcohol and then wipe the contacts on the board again (this will help dissolve crud you can't see), make sure it's dry.
  5. Clean the Assembly.
    1. If there is a lot of crud underneath the key caps (non-original PET kbds) you may want to blow the stuff out now with the compressed air, if there is a lot of gunk between keys, you may want to clean that too (I recommend covering a pencil or pen tip with a towel or cloth, to get in the tight places between keys real good)
    2. Bottom of assembly - you will see little dark rubbery or spongy 'feet' below every key assembly these are carbon conductors which bridge the contact of the PCB's 'fingers', they are somewhat fragile so we don't want to punish them too hard.
    3. Blow out any dust with compressed air.
    4. with the eraser lightly wipe each foot, the eraser will pick up some of the graphite, you will need to clean it (the eraser) off by 'erasing' on the paper after every few 'feet'.
    5. blow out the assembly with the air once more.
  6. Re-Assemble and test
    1. before we put everything all together you should do a partial re-assembly and test that till the keys work, some keys may need more attention (or their 'feet' switched with less used keys)
    2. Fit the PCB back on the assembly and put in those 20 or so tiny screws (don't over tighten or you will strip the plastic threading on the assembly!)
    3. To reduce possible heat damage to the shift lock, do not re-connect yet.
    4. Plug in the keyboard connector into the computer's circuit board.
    5. Turn on PET and test keys.
    6. Note problem keys, if the dead keys are in a pattern (every other every third, etc), you may have a broken wire on the keyboard connector. If it is just a couple keys, you will have to un-attach, re-open and concentrate on those keys.
  7. Keys clean! Re-solder and re-assemble!
    1. Once all the keys are clean you can re-solder the shift-lock wires (and replace the foam insulator if it had one)
    2. If you have a plastic cased PET, BE VERY CAREFUL fitting and tightening those keyboard assembly screws, those posts can snap easier than you think!
    3. Fit key keyboard assembly in the PET's case and partially screw in two or three screws. then check the edge keys to make sure they are not rubbing or stuck against the case, and shift the assembly as needed, tighten screws and put in the rest.
    4. Plug back in the keyboard connector and re-test the keyboard.
    5. If all is well put the prop back in its hook, and close the hood and put back in the hood screws.