Commodore’s datasette is a robust little machine, and many of them still keep spinning. Furthermore, many of the most frequent problems can be fixed easily. This post contains my datasette repair notes, and will be updated regularly.

Before you start

Testing and repairing aren’t always discrete activities when working on datasettes. The items below are the tools I prefer to have available whwen working o As a minimum, I suggest having the following items available for :

• A known working tape
• A known working C64 with a clean tape port edge connector
• A small screw driver, head sice around 2mm
• Isopropylachohol
• Cotton swaps
• Soldering iron
• A cartridge with Azimuth Head Alignment software

I also find it handy to have my component tester and chip tester available. I use the Backbit Chiptester and a cheap component tester from AliExpress.

1. Tape doesn’t load

You test the datasette with a known working tape, but it doesn’t load, no sound is heard from the speaker and no “found” message comes up.

The most common reason for this problem is that the head azimuth setting it wrong. Adjusting azimuth without the necessary software is not easy, but it can be done. I do however recommend using the proper software.

In som cases, tightening the adjustment screw (rotate clockwise) may help out, but it is a bit like navigating a car in the blind.

If the tape is recorded with ABC turbo, and provided you are able to load the turbo loader itself, you may be able to adjust by looking at the rolling strips at the beginning of the load sequence.

2. No signal

You test the datasette with a known working tape, but it doesn’t load, no sound is heard from the speaker and no “found” message comes up. You load Azimuth Head Alignment only to realize that there is no signal at all.

First and foremost, tou should try wiggling the tapedeck connector a bit. You should also do a physical inspection to ensure that all the pins in the connector are intact.

Second, check that the wires from the R/W head still are connected to the PCB. This exact part of the design is fragile, as the wires are soldered directly on to the PCB while the the R/W head assembly is a moving part. Eventually, the solder joints may get damaged.

If the connector and wires are intact, you need to remove the PCB and check the components. The 1530 service manual lists six different PCB versions. With the exception of assembly #320009 and #320109, all of them (#320275, #CMR-001-0, #NP-090 and #017-5001-0) are equipped with a 74LS14 which is likely to fail and cause the problem.

For #320009 and #320109, I have seen the same problem being caused by a failing transistor. Essentially, you should check all of them.

3. Signal bar shows up far right

You test the datasette with a known working tape, but it doesn’t load. You load Azimuth Head Alignment and see a signal, but there aren’t any vertical bars. Instead, you see some black pixels showing up to the far right of the picture. There may also be some noisy dots all over the place.

In these cases, the first thing to try is to clean the r/w head with isopropylalcohol. Keep cleaning until all the brown stuff is gone.

4. Hatch won’t open

You press Eject, the hatch opens but only a few millimeters and then it closes again.

The issue is cause by a small metal arm (see red arrow) being bent slightly out of shape. When the eject button is pressed, the hook under the metal arm is supposed to push the arm upwards, but when the arm is bend out of shape, that won’t happen. To fix this, you simply bend the arm back so that it touches the hook when the eject button isn’t pressed.

5. The datasette is noisy or eats tape

Two different symptoms here, but the root cause might be the same. The first symptom is that when the datasette is supplied with power, it makes a lot of noise even when no tape is inserted and no buttons are pressed.

The other symptom is that the datasette “eats” tape. When you eject a tape, it will be hanging out of the cassette and may be squeezed bwhind the pinch roller.

In some cases, these issues are caused by the small securing ring on the capstan. Under normal circumstances, the securing ring is pressed al the way down to the mount, meaning that the keeps the large drive wheel on the bottom of the tape mechanism in place, but it can somehow move out of position and cause both the aforementioned symptoms. Most of the time, you just need to press the drive wheel upwards and push the securing ring down.

Tapes being eaten may be caused by the pinch roller getting sticky. In those cases, you may be able to clean the pinch roller with isopropylalcohol, alhough the best solution may be to replace it.

6. Twisted signal bands in Azimuth

You insert the tape, load up Azimuth head alignment and adjust the datasette’s r/w head until you have two nice, straight, vertical signal lines on the screen. And then all of a sudden, the signal lines become skewed, start twisting and may even change place. You may hear a crackling sound from the datasette.

This happens because the tape is pulled out of position by the pinch roller. The picture illustrates the position of the magnetic tracks on the tape. Under normal circumstances, the r/w head is aligned with the tracks, but if the tape is being pulled out of position, for example by being squeezed and folded between the capstan and the pinch roller, the magnetic tracks won’t line up with the r/w head.

The few times I have seen this, the fix was to clean the pinch roller with isopropyl alcohol. It usually takes some scrubbing.