If you are in the market, searching for a C64 or similar , you will come by those listings where it either is stated explicitly or soon becomes clear that the machine wasn’t tested recently. But how big is the actual risk of buying a untested hardware?

Some background

I keep detailed records of all my purchases, including repair notes for all the computers and peripherals that I repair. Among the advantages of maintaining these records is that it allows me to reuse my repair notes whenever I come by a device with similar symptoms.

Equally interesting, my repair notes provide valuable insight into the overall health status of the generation of computers and peripherals which was first released into the marked in the 1980s.

Risk considerations

With few exceptions, the items that I purchase are sold as “untested”, although it happens now and then that I buy known good or known defective equipment. But the point of this post is to share some insight into the risk considerations when buying untested hardware:

What is respectively the risk of ending up with something, which is completely beyond repair, repairable with a significant effort, repairable with little effort or just plain and simply in perfect working order?

On the basis of my database, I made a statistic covering Commodore 64 and Commodore 1541/1541/1541-II floppy drives.

Commodore 64 and variants

	Commodore 64 / C	C 64 Longboard	C64 Shortboard
No fix / mainboard replacement	11%	12%	8%
Complex repairs, soldering needed	30%	35%	22%
Minor repairs, no soldering needed	7%	4%	10%
Working condition	52%	38%	60%

If you are in the market, looking for a C64, buying an untested machine is getting risky these days.

Nowadays, chances of getting a working machine is close to 50/50, but the risk is significantly bigger with the longboard-based machines (most breadbins) than with the shortboard-based machines (most C64C’s, Aldi’s and C64G’s).

If we include minor repairs (cleaning of contact surfaces, fuse replacements, replacement of key caps and other errors which can be resolved, using nothing but contact cleaner), you should expect luck to be on your side in 70% of the cases for the shortboard-variants but only 42% of the older, longboard-based variants

For both longboards and shortboards, you should expect 1 in 10 machines to be in a state where repairs are unfeasible. This covers dead SID-chips, serious corrosion damage and complex defects requiring multiple hours of troubleshooting.

And then there are the feasible repair jobs, which however require technical skills and equipment: 30% of the longboard-based machines and 22% of the shortboard-based machines had errors, which can be fixed in a reasonable amount of time, provided you have technical skills skills and equipment.

Last but not least, respectively 4% and 10% of the machines, which only required minor work such as cleaning of contact surfaces, fuse replacements. replacement of key caps and everything which can be resolved, using nothing but contact cleaner.

1541 family of floppy drives

The story is quite similar when it comes to floppy-drives. For floppy-drives in general, the crucial part isn’t as much the electronics but rather the R/W head. For the same reason, the percentage of critical defects isn’t as much a question about the generation of the product, as the R/W heads found in the earliest Alps-drives are more reliable than the R/W heads found in later Newtronics / Mitsumi-based 1541-II and 1541C drives.

For those reasons, I didn’t do separate statistics for the various product generations.

Across all variants, chances of finding a working drive is slightly above 50%, and if you are able to clean the R/W and lubricate the drive mechanism, you should be good to go in nearly 2/3 of the cases.

There is however no doubt in my mind that the by far highest probability of success is found on the later Chinon-based 1541-II drives. If you are skilled with a soldering iron, just about any Chinon og Alps-drive will be fixable, although the chances of a working mainboard is significantly higher on the 1541-II drives.

	Commodore 1541 / C / II
No fix / mainboard or drive mechanism replacement needed	11%
Complex repairs, soldering needed	24%
Minor repairs, no soldering needed	8%
Working condition	56%