so, speaking of the infamous capstan motor, does anyone have a schematic? digging into the deck, it becomes pretty quickly apparent that the circuitry, not the "motor" itself, is what fails. i keep on putting off shelling out $100 to get a new motor for mine because i remain convinced there must be one of those little dinky resistors or diodes or whatever else is on that board that i could replace for pennies... but without values, nowhere to start
..a monster thread of which the gist is that those same little silver capacitors, when they fail, kill the Dolby S chip, so replace them before that happens, and that that is very fiddly, exacting work requiring a tech experienced with micro circuitry and the precision tools involved.
Tascamwiz of Tascam Forums on Dolby S chip failure wrote:
?90% of the TSR/MSR Dolby-S machines I have worked on (probably more than 20)have problems with the NR in one way or another. Scratcing noises, channels fading in and out, full signal distortion (blowing the studio monitors in the process), just plain dead(no NR at all), etc.....Fostex is not much better, and a whole LOT of Dolby-S cassette decks with malfunctioning NR.....especially the Sony ES and Teac V-8000/8030 series.
Again, it is likely that the issues are caused by tolerance drift of aging circuit components. This coupled with a sensitive Dolby LSI chip causes them to fail at which point circuit diagnosis is impossible. I have tried many different sources for some of these ic's both in the USA and abroad.....no dice. When the chip foundries stop making a particular they apparently do not save the masks and wafer production equipment. There are several different types of Dolby-S NR ic's depending on application and it appears that some major oems like Teac/Tascam had some specific parts made for their machine design.....mainly in bus control and interface logic.
The problem is by the time you hear audible artifacts or notice impaired functioning, the damage to the ic's is most likely already done. The other issue is that unless you happen to live near a shop that can work on these machines, you can rack up $200+ in shipping charges .?
"The interesting thing about Tascam machines in particular is that they can use either the DBX or Dolby-S cards interchangeably as long as they are in the same enable/disable bank. They use the same switching logic interface for both card versions. I had some spare DBX cards for the 238, so I outfitted that particular machine with 4 Dolby-S cards and 4 DBX cards.......worked perfectly fine and the owner was actually happier with the way that worked out. Same thing applies to the TSR/MSR series. If you have one of these machines with bad Dolby cards, you can swap them for DBX cards if you can find them."
witzendoz of Tascam forums on preventing Dolby S failure wrote:
"My Machine had the late type boards, the dolby S failed because the caps went out of spec, as simple as that. What I did was find a tech that could solder the micro caps onto the circuit boards. This is specialized work and needs a lot of skill and special tools, as each board failed I got him to fix it. I also had a spare card which I bought to replace the 1st failure (did not know the problem at that time), so I always had a fixed up board on the shelf to keep going. The repaired boards worked fine and the caps were of better quality than the tascam ones so they will probably outlast me.
The components are off the shelf and even the high spec caps are cheap.
Keeping old gear alive is always a labour of love, its like people that restore old cars (and I was one of those once as well), sometimes you have to source parts and workmanship but at the end you get the reward of have a fine piece of old gear.
Studio-Integra of homerecording.com said:
"Just replace the SMT caps on the motor PCB..."
"When I got my 238, the capstan motor was also spinning too fast.
I have replaced the caps and it is working perfect now."