Tascam 238 - forward & rewind problem // solved

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pixedelisme

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tascam 424, tascam 688
Hi everybody a friend gave me his tascam 238 for repair: cassettes don't want to rewind or fast forward. Only playing tape is good. I changed all the components I could (electrolytic capacitors C5, C7, C9, C13, C15, the ceramic C2 & the zener diode) on the capstan servo motor. but that doesn't work. when a tape is completely rewound I can fast forward but very little time. when I nsert a cassette in the middle of its duration it does not work at all. Does someone have an idea ? Is there a particular motor that takes care of rewinding or fast forwarding? what is the name of the 2 motors (see picture) is what can cause troubles ?
thank you !
https://ibb.co/4F62RJt
 
Hello,
the capstan motor does not have anything to do with the rewinding and ff functions. It is the role of another motor. It drives through a gear an idler roller which should be replaced by default too. Maybe the gear is broken too, or the motor has some fault. On another note, it was good idea to refurbish the capstan motor board, it is a ticking bomb without this. upload_2021-5-25_0-42-36.png
 
thanks for the reply Laszlo, i was expecting it a bit ... is there any chance to find a tutorial to taking apart this motor? i didn't find on youtube
 
Maybe someone will tell, but per se there is no such tutorial out there. The 238 transport is almost the same as the 122MkIII, so if you download the service manual, you get some drawings which you can use for dissassembling it. These motors are quite common DC motors, probably you can find replacement, but I would first check the gear and the idler rubber wich tend to get stone hard.
 
well i find a new motor cheap same number (RF-510T) but it seems that is not the same idler roller. do you think it comes off? looks like it's hard to remove
 
If you mean the idler rubber, you just brake it and remove from the idler. There is replacement rubber on Ebay, I also bought it from there.
 
no i mean the roller, plastic part - as on the picture here https://ibb.co/phGRmzZ
so i break it and find the whole thing for 238 ?
 
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Dont break it, only the rubber that is usually obtainable. There should be a way to get the assembly off the motor shaft. I never had to do it, so better to ask someone who did it already. Maybe Sam (
SkywaveTDR) if he does not know, noone does :)
 
The Idler tire is what I change and I use a square seal from Mc Master Carr. Those expensive E bay tires are just regular rubber and will harden and wear out faster. My seals work well and have a 10 year shelf life. I tested these in many decks before I let the cat out of the bag. Motor on these usually do not need to be changed yet. I had one deck where the plastic shrunk and caused too much friction to the turning shaft. I use a drill bit to widen the tiny bit and then it worked correctly after that. I also apply AMSoil to all motor bearings as they spin much better once it works in giving you high wind speeds. Reel tables can also be oiled and then they don't screech like they do sometimes.
 
I rarely buy anything on E bay as they 99% of the time are wrong parts. They are just people looking to make money selling anything that they want- they rely on the laziness of people not to send the wrong parts back and that works almost 100% of the time. The Idler is changed by taking the two screw out behind and under the cassette holder. This is removed when I do cleaning and mechanism grease replacement. The screw are Ms and very short so don't drop them as longer ones will not work. Once the screws are taken out the motor with idler drops out the back. I have done 100 of them at least. Don't forget to Deoxit the Pin switches adjacent to the cam motor as these can cause the deck to stop intermittently- they are linked mechanically to the detection levers for record enable and tape in detection.
 
Keep in mind that the reel drive motor is not only for fast winds but that in a lower level of drive it also provides cassette take up torque. This is when the motor will be found to fail as the slower a motor goes the more likely dead spots on commutator will be detected. Fast wind has rotor inertial to keep it going. Often times the new motors you put in will have different screws than what you take out. I have not had to change too many motors on reel drive of these decks. Idler tires yes- they crack and some are even found in the bottom of the deck- the deck will not work at all with a bad idler tire on it. A cracked one can give the symptom of the motor dead spot but the crack tire is the problem.
 
Thank you SkywaveTDR for your precious advice. I was able to easily taking apart the motor and see the idler. As you can see on the picture i don't see anything broked.
https://ibb.co/xD7ZtdP

the idler of the tascam 238 (on the right) is different from the one I found (on the left). it's really strange as problem, it looks like the motor lacks power to advance or rewind when there is too much tape ... what is the ceramic capacitor on the motor for? can it break down if it is broken?
 
I had a weak motor too but it turned out to be shrunk plastic on the rotating shaft. I took off the plastic piece and slid a drill bit through the hole allowing it to clean any burrs or to open it up a little bit. Being the shaft is also rotating inside this plastic I may have put some oil. In the end with new tire the system passed all my tests. I only test deck with C-90 as they are not designed to work with C120 and C-110 are the same tape.
The C2 on the servo card is close to the Zener diode. I suspect it is used as a filter but the humidity and temperature coefficients are so horrible that it changes the circuit as the guy in video found out. This is when my schooling kicked in about parts- that use of a Polystyrene cap would be of the best you can put in there. Some use Wima film caps and I don't think it makes a big difference except that you need to get away from that 1 cent ceramic garbage they put on there- it is like they spared no expense in finding out what was the worse garbage to put on this board starting with SMD parts. If I was to redesign this PCB there would be NO SMD parts on it.
I do not recall seeing that much difference in the motor assemblies like you show.
The one type that I had to use drill on was the type on the left.
 
no i was talking about the only one ceramic on the little motor (see picture here : https://ibb.co/PYfjB72)
It's been a little while since I looked for my problem and I saw that it was advisable to change all the capacitors on the drive motor so I have already done it. well i think my last chance is to spray oil on the gears ;-)
 
eureka everything works !! it was the little spring which did not push the rubber enough, I took it apart and retightened everything works thank you all !!
 
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Don't spray oil and the gears would need grease. Spraying a lubricant is always a bad idea. Then one wonders why the idlers are slipping. Well you fixed it now keep fingers crossed.
The noise mitigation cap on the reel motor is not the one I was referring to. The C2 is on the capstan servo but this deck may not use that motor.
 
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