View Full Version : 8050 PET Drive

September 30th, 2007, 10:09 AM

i am now the proud owner of a PET 8032 - with matching 8050 drives.
however the drive lights all keep flashing. single centre green, then all on - two green and centre red.

as you would imagine the PET cant access the drive.

i have opened it up and the connectors seem fine and the chips seem seated.

erm.. any ideas from here?


September 30th, 2007, 11:43 AM
From the 8050 service manual:


On power up, the three LED's on the drive should blink. The drive LED's go off and the center Tri-State LED remains green. The system has a built in self diagnostic which can be read in the form of a flash code. In the event of a failure, the 3 LED's will blink in a repetitive sequence. The number of blinks between intervals will indicate the possible location of a failure.

ERROR INDICATIONS (#F means number of flashes)

1 Zero Page 6532 UC1,UE1
2 ROM $E000-$EFFF 2364 UL1
3 ROM $C000-$DFFF 2364 UH1
4 Unused
5 Zero Page 6530 UK3, 6502 UH3
6 Common RAM $1000-$13FF 2114 UC4,UC5
7 Common RAM $2000-$23FF 2114 UD4,UD5
8 Common RAM $3000-$33FF 2114 UE4,UE5
9 Common RAM $4000-$43FF 2114 UF4,UF5
10 Controller ROM 6530 UK3, 6502 UH3

If the LED's come on and stay on, the microprocessor UN1 is probably at fault.

Good luck with locating the fault. In the worst case, I might be able to sell you components, a new motherboard or a whole drive (if you mind the steep shipping). PM me if that is an option.

September 30th, 2007, 11:53 AM
so from that description i should take it that:

once the centre lights comes on as green - then goes off to start the blinking pattern - which continues until the centre light goes green again?

the number of blinks between both steady centre greens?

-as a follow on from this - can any of these issues be fixed without having spare parts lying around?

and am i correct in thinking that a vic20/c64 tape deck would work?

sorry for the newbie questions - if indeed thats what they are.


October 1st, 2007, 12:16 AM
Yes, the C2N (1530) is fully compatible over the whole range of Commodore 8-bit computers, with the slight exception of the Plus/4 and Commodore 16 which use a different type of plug but electronically are compatible. Software from a different machine may also be loadable (but not runnable).

I think you would need replacement chips to solve any fault. The 6502 CPU is quite common if you ask the right people. The 6530 and 6532 may be a little harder to come by, but not incredibly hard to get. There also might be modern replacements. The 2364 is a PROM (?) which could be replaced by an EPROM using an adapter circuit. The 2114 is a RAM chip, but I don't know how easy it is to get hold of. Most of these should be socketed with the exception of RAM.

October 1st, 2007, 05:37 PM
When you power on the 8032, and it's properly cabled to the 8050, and the 8050 has already been on for a few minutes....
..you should expect a red-green-red-green exchange and then the green light should stay on. If the drive *continues* to blink, count the number of blinks in the pattern.

The flash code chart Anders posted will then tell you which chip is bad, but there may be more than one. You only get one flash code at a time. You may fix one chip and then get a new flash code for a different bad chip. Once the flash codes end, you're done.

Let us know what you find. I have extra boards for this drive.

P.S. most of time the PET-->IEEE cable will be plugged into the units with the C= sign pointing upwards.

If you want more testing ideas, read #11, #12, #15 from this page:

October 1st, 2007, 11:16 PM
Fortunately, many IEEE cables are keyed so you can't push it in the wrong way without a lot of force. Certainly you can insert it into the wrong slot, i.e. the nearby user port depending on which host computer you use.

October 3rd, 2007, 05:48 PM
I have one IEEE that's upside down (the C= goes on the bottom for some reason) and another without any markings. I have the "normal" ones too.

October 6th, 2007, 12:05 PM
howdy again folks - sorry it took a bit to get back to you.

ok - looking at the LED flashes i am guessing its the Zero Page error, as the lights flash in a steady pattern without any change.

i have checked the 6532 chip at both locations and both seem to be seated.

i have also swapped around the IEEE cable to check, ie 'Commodore' facing up and down and still nowt.

So the chips it is then.

or even an online seller you have used. i am in the UK by the way.