Teac A3440 parts commonality

[suebutcher]

Season's greetings. I'm working on a neglected Teac A3440 tape recorder. It seems fixable, but the capstan roller had surface rust. Now that I've cleaned it off, the surface is covered in tiny pits. The roller feels smooth, but I'm worried about the effect on the tape; if the rest of the machine checks out, I'll look for a replacement capstan. A3440 parts are getting hard to find, though. The question is, what other Teac or Fostex machines also used this part? Here's the specs:

Capstan overall length 74mm
Capstan roller length 18mm
Capstan roller diameter 12mm
Capstan spindle length 56mm
Capstan spindle diameter 6mm

[John Caswell]

Hi,
Well it might be worth refitting it to see what happens, obviously using a rubbish tape.
Failing that there are companies that can "sputter" new material onto it and regrind it to its original dimensions.
Nagravox in Sydney may be able to help/advise

John

[TIMTAPE]

It does look rough but when new they're sand blasted to a mildly abrasive finish. As John says it might be worth trying it out, (with a new well adjusted pinch roller) and see how the tape copes with it... More of a problem might be cyclic speed variation due to being not completely concentric any more if the rust was worse on one side of the shaft than the other.

I think from memory the previous A 3340 used the same shaft although the capstan motor was a much more rugged AC type.

With the 3440 you could perhaps have the capstan area lathed down just enough to remove the damaged surface. The diameter will be slightly smaller but the 3440 uses an electronically adjustable DC motor so it could probably be trimmed back up to standard 7.5/15ips without issue.

Be careful, the small DC capstan motor works fine if everything is in order but it has little tolerance for overloads such as playing sticky binder tapes, or sometimes when the tape on the supply reel wont release at the end of the reel and the motor can grind itself into destruction while the owner is out of the room and oblivious. The replacement motors are still available but not cheap.

Also if there's been a lot of rust on the capstan shaft there could be even more inside the machine. With a range of similar Teac machines, printed circuit boards had the printed tracks facing upwards. Dirt could accumulate, attracting moisture. The tracks under the lacquer can corrode badly, requiring a lot of time consuming work to repair them. Might be worth inspecting this if you haven't already.

Tim.

[suebutcher]

The pits aren't deep, so perhaps the capstan could be reground. The inside of the machine looks OK, but the debris from the perished capstan belt has fallen on the switch circuit board so I must check this for corrosion. Typical story, it was given to me not working and I put it in the shed, but it was so heavy I couldn't easily move it into the house. So I forgot about it. I've got a garden cart now, no worries!

Picture shows internal dust, and the usual rusty screw heads you get on the outside of Japanese gear. The stuff that looks like fag ash is the dried up remains of the old belt.

[suebutcher]

By yesterday all the mechanical functions were working, so I tried a thirty year old four channel music recording - not one of my best - and the playback was fine. No damage to the tape from the capstan pits either. But the capstan was shiny from the rust removal, and I don't have access to sandblasting gear to restore its original grippy matt finish. What I did instead was remove the capstan and roll it between a table and a plane surface, both covered in 240 grade wet-and-dry. (Bearing shaft protected with masking tape of course!) With a lot of hand pressure and ten minutes rolling, this is the result.

[John Caswell]

Hi Sue,
Well looks pretty good to me and if it works OK what the heck.
Out of curiosity record and playback a 1KHz tone to see if the work has had any effect, especially "flutter" as according to Tim the absolute speed can be adjusted electronically.

John

[TIMTAPE]

The relatively large diameter shaft on this model means there's lots of surface area to grip the tape so slippage normally isn't an issue, even without the sand blasted finish.

It also helps that the pinch roller surface is flat and wide. It not only presses the tape onto the shaft but on either side of the tape it contacts the shaft itself. So as well as the capstan shaft drive, the pinch roller is driven directly by the shaft, and so also drives the tape from its back side.
This works on the largish diameter shaft but on smaller diameters it can cause problems as the front and back sides of the tape are more forced to move at two slightly different speeds. Even on the 3440 you can sometimes hear a squealing sound from the capstan area which I've always assumed is the sound of the tape caught between these two slightly conflicting speeds.

On other tape machines with a smaller diameter shaft, the makers do the opposite and make the pinch roller rubber no wider than the tape itself, avoiding the problem of the two slightly different speeds.

[suebutcher]

I put my test tape through the machine yesterday, and everything seems fine. I haven't touched the heads, they're original and are still at the factory settings. Even though the wear is obvious, there was no trouble adjusting the play response back to flat using the trimmer pots. No audible flutter either. It's a keeper! I may not need my Ferrograph Seven any more.

[suebutcher]

Here's another parts interchange question. One of the reel tables has a broken spline. Obviously the Teac A3340 and A3440 reel turntables are the same part, but I can't find one for sale a reasonable price. Will a Teac/Tascam 80-8 table fit? Apart from the rubber mat and the different reel retaining hardware (the 80-8 is a 1/2" machine), they look like the same part. If Teac was as cost-conscious the Ford Motor Company they'd have to be the same part, but I don't know Teac that well.

[suebutcher]

Answering my own question, they are the same part in this case, though the reel tables may have changed on later 80-8's. At present the 80-8 is poorly regarded, so these machines are more likely to be broken for spares than an A3340 or A3440, making 80-8 reel tables a cheaper option.