Failing drive belts among the most frequent problems you encounter when servicing Commodore 1530 and 1531 datasettes. But when should you replace the drive belt and how do you do it?

Commodore’s many datasettes

As illustrated in Giacomo Vernoni’s eBook on the topic, Commodore produced an impressive range of datasettes for use with its range of Commodore’s 8-bit computers.

In this post, I will focus on the later range of datasettes produced for the VIC 20, C64, C16 and Plus/4, i.e. the 1530/1531 going forward. I call it a “range” because there are multiple variants in terms of both the visual appearrance and the internal workings.

As is the case with most of Commodore’s products, the 1530/1531s were made from standard components sourced from various manufacturers. There are two main lines of datasettes produced in respectively Japan and Taiwan. The Taiwanese model (see the right photo) had black tape counter wheels with large, white digits and the Record LED was located near the tape counter. The Japanese line had white counter wheels with small, black digits and the Record LED was located above the Record button. Electronically, the service manual lists six different PCBs. The mechanical parts are however quite similar, and in regard to drive belts, they both use 75mm / 1.2mm square belts as main drive belts. The tape counter belts are 59mm / 1.2mm square belts.

Belts gone bad

What does a bad drive belt look like? I have included a couple of photos. In the first photo, you see a new drive belt (left) and a bad drive belt (right). You will notice is that the bad drive belt has developed a dent from being stuck in the same position for 30+ years.

Below, you see a another good belt on top of a bad belt. You will notice that the bad belt has a visibly larger diameter, even if it remains almost circular.

Belts with dents may still work, but if the dent prevents the tape from running at a constant speed, it is time for a change.

Replace or not replace?

This may be a matter of opinion, but with the exception of preventive repairs (removing leaky batteries and caps), I don’t repair anything unless it has stopped working properly. There is always a risk that losening a screw causes 40-year old plastic to crack etc.

Convince me otherwise but replacing a drive belt serves no preventive purposes. As long as it works, it works. When it stops working, I replace it.

I rarely replace tape counter belts, as I usually find them to be working satisfactory. The amount of load on the tape counter belt is limited, as it only drives the counter. The load on the main belt is considerably larger, as it not only drives the tape but also the tape counter.

In my experience, main belts fail way more often. In a recent lot of 17 datasettes, I replaced 5 main drive belts and no tape counter belts.

If I experience any of the following symptoms, I replace the main drive belt as it usually solves the problem:

• The spindles run at normal speed without a tape inserted, but when the tape is inserted, the speed drops or the tape stops running.
• The tape drive has difficulties driving long tapes, but works with shorter tapes.
• After “Found” is shown, doesn’t recommence loading automatically. You may still be able to complete loading by pressing stop and play manually. The spindles appeared to run at normal speed.

How to replace a drive belt

Replacing a main drive belt requires that you remove the small screw on the side of the wheel mount (red arrow on the left) and loosen the screw holding the cover plate (red arrow on the right). You don’t need to remove the PCB. I usually put the belt in place around the black spindle wheel. Then, I pull it through the opening in the cover plate and position it around the large capton drive wheel before I finally connect it to the motor.

When replacing the tape counter belt, you don’t need to remove any screws. Simply raise the arm (red arrow) that releases the tape door, and put the belt in place around the spindles on either end.