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.

Tascam 234 4 track tape transport

Looked nicely laid out and well constructed as all this old Tascam equipment seems to be. I thought I’d just take the transport out and it’d be easy. There are just two belts in the 234, the capstan belt and the belt that moves the transport up and down. This cam mode belt had stretched and come off and the capstan belt had pretty much disintegrated. Once I start I find it hard to stop and this isn’t a quick job the first time, you need to be methodical and patient, good screwdrivers help too.

Well here comes the process, it seems pretty daunting at first when you see how many boards, cables and bits you have to remove and disassemble to replace the belts.

Remove Transport

The transport must come out to change belts. The capstan motor and cam motor have to have their mounting plates removed to change the belts and as far as I can see this is impossible unless you remove the transport.

1. Remove all screws holding the transport in. These are on the top and base. Be careful not to round and of the screws.
2. Turn the deck upside down and remove the half of the base plate under the main PCB.
3. You should now have access to all the transport connector blocks. Carefully remove these and clip any cable ties holding bundles together.
4. Now you need to unscrew the pitch control bracket from the front fascia. To do this you’ve got to take the front fascia off, that means all the knobs have to be pulled and the screws top and bottom removed. Remember too the little hidden screws holding the transport control buttons. These are in recessed holes access from underneath. Be careful not to remove them totally and then loose them on the floor like I did! Just undo them a little so the panel comes off and lets to remove the whole fascia so you get access to the power button.
   

   Tascam 234 transport, prepare for removal

5. Now you can unscrew the main power button which will let the transport lift out much more easily.
6. Very carefully ease the transport up and angled out of the machine. Be careful not to snag any cables. You’ll need to be firm but gentle..

Replacing the Belts

1. Now you’ve got the transport free, give yourself some space on your workbench and have a look around the transport to familiarise yourself with it.
2. We need access to the motor and capstan area underneath the control PCB.
   

   Tascam 234 transport control PCB removed

3. Undo the two screws on the control PCB and carefully lift it up so you can unslot the PCB from it’s hinge at the other end.
4. Now you can almost access the cam mode motor and the capstan but you need to remove some more screws.
5. This is where it starts to get tricky! You can do the cam mode belt first. This is the belt that is square sectioned and moved the headblock up and down depending what the tape deck is trying to do.
6. Remove the three screws that hold the metal plate down that the cam mode motor is fixed to.
7. You can now lift this up, and get the old belt out and hook the new belt around the large pulley while lowering the plate back down. You must lift the plate, the belt cannot be replaced without doing this.
8. WARNING – Make sure you clip the white gear with the slot over the section in the large black cam wheel. If you forget or don’t do it right the PLAY, FF, RW etc modes will all be wrong and not work and you’ll have to take the transport all out again! Beware I did it!! I don’t have a picture of it as I was so annoyed at having to do this all again I forgot.
9. Now you can screw the plate back down and using tweezers or a bent paper clip hook the cam belt over the motor pulley. I think I managed to put it on while the plate was off and get it back on without it falling off.
10. Now for the capstan pulley which I found the hardest.
11. Remove a few more screws to lift the plate the capstan pulley and motor is attached to. Now the capstan can be lifted out. Be careful to lit it straight up and not bend it.
12. This is a good time for a bit of lubrication. Put some very light oil on the capstan shaft where it goes into the bushing. I use Prolong Precision Oil which comes in an easy dispenser. Also using IPA clean up the capstan wheel if there’s any left over trace of old belt and put a dab of grease on the end of the capstan where it gets held by the capstan plastic tension screw.
13. What I did next was hook the capstan belt over the capstan, trying not to get any grease or oil on it, then pull it over the motor pulley. You kind of have to hold the plate and motor taught in one hand while you do the belt threading and also keep this up when you relocate then plate in the transport with the screw holes lined up – Took me a few attempts but I got there in the end.

Reassembly

1. Reassembly is the reverse of disassembly as Haynes manuals often say! Just dont rush and it’s worth checking the belts are really on correctly and the little white bit in the cam gears is located correctly.
2. Put the rest of the transport together, the control PCB and relocate the wires that you may have disturbed. There’s black stiff wire that can be wrapped around the cables to stop them fouling anything moving.
3. Put the transport back into the deck but take care to locate the cables so they’re not getting fouled or pulled to tight. You did take some digital photos before you took it apart didn’t you?
4. Remake all the connector connections. You can’t really get these wrong as they are colour coded and different sizes.
5. Screw the power switch back on.
6. Feed the transport control panel cables back in and hook this up to the front panel.
7. Relocate the front panel. You may have to move the VU meters a little to get it to slot back in and nudge the push switches. Just don’t force anything.
8. Almost done now. Just screw everything backup and switch on!

Testing

1. Double check all your connections are right and you haven’t left any screws of tools lying around inside the machine!
2. Power it back on check the transport functions. It should move into play, FF, RW, STOP etc smoothly and quickly. You may need to adjust the STOP control POT to make sure the head base is at it’s lowest position when in stop. Use a ceramic adjuster for this if you have one.
3. If everything is working well done. If it doesn’t go into STOP properly and let you eject and it eats tape you’ve probably done what I did and not locate the cam mode gears / followers correctly and I’m afraid you’ll have to take it all apart to fix. It’s go much quicker the next time though if it makes you feel any better!!