capstan motor

8 track cassette capstan motor tascam 238 syncaset

We specialise in tape transfers, especially cassette tapes.

Tascam, Fostex and Yamaha sold cassette multitrack recorders in the golden days of home recording in the 1980’s and 90’s. The 4 track format was especially popular but an 8 track format was also developed that squeezed even more out of the small tape width of the cassette.

We love these cassette formats and their accessibility helped start many musicians’ careers. Unfortunately one of the best 8 track machines, the Tascam 238 Syncaset also suffers from a common and frustrating problem that renders most of these machines useless over time, the dreaded direct drive capstan motor failure…

The 238 and other 8 track and high quality stereo tape decks, the 688 and 122 MkII and III, used a direct drive capstan motor for precise speed control and reduced speed variation or wow and flutter (w/f). The circuit that controls this motor fails in certain ways causing lack of speed control and in our case the capstan motor wizzing away at a crazy speed, not the 9.5 cm/sec that it should do.

This here is the culprit  – you can see the attempted repairs which didn’t ultimately work.

One common failure is that the surface mount electrolytic capacitors fail or their capacitance changes to such an extent to cause speed problems. These can be changed for standard through hole caps but you do need to be very careful as the tracks are damaged very easily – good tools are essential.

The other point of failure in the circuit is the BA6304F SO16 IC – we even changed this but the motor still didn’t turn!

There was some suggestion from previous repairers that the grease at the end of the capstan flywheel hardens over time. increasing the friction and causing problems with the circuit.

This can become frustrating quickly, especially when you have a large archive of cassettes to digitise.

When we can’t repair we reluctantly do the next best thing and buy the whole replacement part but this is another exercise in frustration. Teac parts and Teac UK don’t have any european supply of this capstan motor (part no. 53700075-01) anymore as of November 2011. Interestingly about 6 months ago they did at around £60 GBP, then about 3 months ago they had one left at £160 GBP!

Lots of emails later to Teac US, Teac Canada and Teac Japan there seem to be a nice stock still on shelves somewhere and at reasonable prices UNTIL you ask them to ship to the UK when you discover they can’t do this and I’d need to go through Teac UK!!! I’m pretty persistent but I gave up finally even though some of the support staff tried to be pretty helpful.

We find support for older machines from the original manufacturers is not good generally and unreasonably expensive when you can find it. This is similar across audio and video, semi-pro and professional products. Some companies are easier to deal with and have better parts situation than other but stockpiling machines, parts, manuals and obsolete knowledge is the best course of action.

What we finally did that worked and was a good solution was purchase 3 Tascam 122 Mk III stereo cassette decks which use the same but a later revision of the capstan motor, (part no. 53700121-00).One machine was donated for the cause and the capstan motor removed, modified and refitted in the 238. The 122 motor has a few factory extras, such as these resistors, shown here:

You also need to solder / desolder the speed pads, to change the motor speed from 4.8 cm/s to 9.6 cm/s that the 238 needs to run at.

It’s also a good idea once you’ve got the capstan motor apart to clean the old grease from the seat, check the end float which can be adjusted using the screw shown on the left and apply new grease to the capstan end.

Put it all back together – be careful to solder the wires to the motor to the correct pads – they’re different on the 122 and test… Ours worked almost perfectly.

As the transport hadn’t been used for a while the reel motor would intermittently stop as if sensing the tape end. This can sometimes be loose counter belts but on the 238 it’s a digitial counter. We cleaned up the leaf switches on the transport top and also sprayed a small amount of deoxit into the inside of the reel motor. A bit more use and it finally worked to spec…

For 4 track and 8 track multitrack cassette transfer please contact us for more information.

 

 

Posted by greatbear in Audio Tape, 8 comments