TASCAM 122 MK III capstan motor help

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gavin a keable

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Hello,

I have said 122mk iii, I recently opened up and found the notorious broken "Gear C" and replaced it. I also replaced what i believe is the idler rubber roller. So this had the classic running extremely fast capstan motor problem that I have read about in this forum. My original capstan motor control board showed definite trace damage from the caps leaking over time so I decided to replace the SMD electrolytic caps myself. After completion there was no change in behavior. I then decided to purchase a $115 replacement capstan motor control board from Ebay. Now after replacing that... there is NO capstan motor movement at all. FF and RW works flawlessly yet no capstan motor. I'm really hoping a fellow member can help ascertain my problem.
The board I bought was from seller "jpsolarsolutions" Item number 302503922051. I hesitate to think the board is faulty. but I do notice a slight difference in component parts/ traces compared to the original. What I can tell is that the board is getting power and also the windings that needed to be soldered back on all have the same resistance to their respective pairs. I can provide pics if needed. thanks everyone
 
PXL_20210521_180446174.jpg PXL_20210521_180742269.jpg

Above is my original board removed with new SMD electrolytic caps installed. Note the considerable trace damage. Lower image is my replacement board installed. I have noticed a small difference around IC-1 and also a jumper pad just below IC-1 . If anybody can help, I would appreciate it.
 
Well the main reason the E bay board does not work is that the motor coils are missing from the other side. Why would anyone make a board the same wrong way that they did in the first place? The SMD parts in my case are removed and the board repaired in using an DVM to detect broken traces. The edge trace is a ground so that needs to be going to all the places that it was going before. Since none of this is high current I have used 30 ga telco wire and then some smaller gauge wire wrap wire to duplicate traces compromised. I have some motors still being worked on but out of about 135 motors I think I have made 133 good ones. My motors have part either sticking up or mounted so the parts are slightly laying down. It all depends on where they need to go into. The 122 k III is a lot tighter than the 122 Mk II but other decks- some do not have any problem at all. The Mk II is also notorious for the falling apart pitch control pot with 4 terminals that can not be repaired. I have in some units come up with a mod with a 1 million operation plastic conductor linear pot but due to shaft length there is plenty of doctoring to mount it so that the same original knob a D type can be placed at the same position and orientation. I hate surface mount parts as they were never made for a long term devices- only throw away cell phones that last a couple of years. It is junk.
 
C2 needs to be upgraded to a .01 Mylar as it is a filter and goes much better at that size. I had been using .001uFd Polystyrene with no trouble either but the .01uFd is said to provide better filtering. I do not trust any belt kits or parts from E bay at all and I never buy that junk.
 
@SkywaveTDR , Thank You for your time and for your help. My first question is about the motor coils. I thought I could de-solder the coils from the old board, then swap in the new board and solder them back in place. Are you saying that the correct way to replace this board, is to included replacement of the motor coils together like an assembly(assuming that is an actual option)? I understand your insight on fixing traces and using different components in a more practical way. Also thanks for the great tip for the upgrade on C2! I have spent many years behind a solder iron but sadly have barely touched SMD components! I agree that Ebay is a bad Idea when it comes to most things technical on the bench, I had no idea that this was also a bad idea:(. Lastly, would you recommend going back to the original board? If this all doesn't work, can I send this assembly to you for repair? Most bench techs I know won't work on "hacked" equipment. Or in my case a board that's been worked on already.

Thanks again for your valuable insight
 
Well, the reason that buying that expensive board with the wrong parts on it when it does not come with the coils is bad is because a lot of trouble will be had with those coils. Some of them were put on with stress to the soldered lead. Then also the motors when they fail have a lot of vibration that also stress the wires. I have had many that break. There was one case where the break was under the coil so I had to carefully take it off find the lead and attach a piece of wire wrap and then glue it back to the metal plate. many things are critical in these motors that people do not realize that are there. Lubrication is a very big issue. When I use AMS oil in these they just will turn a long time- the servo board need to be on as it lifts the flywheel up but then there is the thrust bearing setting- some people adjust these willy-nilly. There is a test point on the motor that you can see the FG amplified signal. This should be maximized without waveform clipping. A good number of motors I find lose in the mounting due to the vibration from a malfunctioning motor. Motors should turn without sound. My motors all have through hole 105*C cap with exception of the 85*C Bipolars. The use of a DVM on diode test or ohms can allow you to test traces and if they are dark as in corroding already I patch a wire across them. The outer long trace that is the ground is very often compromised.
On the Board- I would have never bought that other one and just fixed the one you have- they are not all that complex and when I take SMD parts off I use solder which and a Weller and I slide the parts off in the plane of the board. I do not pull up. I have been able to get them off almost 100% without damage to foil patterns but if you have a foil that does come off you can re-establish it with a bent piece of wire wrap wire that goes to the next component. I measured the coils on a Mk II and they were 14 ohms each. These are wired in pairs in series. I try not to work on deck parts- the motor work needs to be done in the deck with the pitch control also examined. If that pot had a broken wiper- it is only held on with a tiny piece of plastic then you need the mod kit that I put in. I was going to sell them for $45 but there is so much variation to putting them in sometimes it is not all that straightforward. Plus I do not have that many part kits here. Alex Nikitin sent me a schematic he did from a deck her had but some of the parts don't match but at least it is a help.
 
I have had my eye on this eBay board for some time, but I have been hesitant to buy it for that price because it requires the coils to be transferred to it. @gavin a keable , it seems like you didn't have much trouble with swapping it over. (looks good, at least). I am disappointed to hear that the motor doesn't rotate at all now.

What resistance do you measure on each coil? I measure about 14 ohms on each coil for my 122 MKIII motor that moves. Just wondering if your coils are still good after the swap. Did you bend the Hall effect sensors over and glue them down to the coil plate, like on the original? Those are necessary for the motor driver.

Also, it's strange that there are polarized caps placed for C12 and C14. Originally, they were bipolar caps. At first, I thought this jpsolarsolutions board was just a revised version of the original motor board that maybe ended up on later built units. You can see how R10 and R15 were added to correct the rework that was required using the through-hole resistors on the original board. But now, I'm wondering what the origin of it is...

I wonder if this eBay board has worked successfully for anyone. I'd be interested to hear about it. If not, then maybe it's full of fake parts and just a scam! :p In your case, I certainly hope not.
 
@steve908 , You just told me what I did wrong without knowing it!! Hall Effect sensors you say?! yeah I bent those the OPPOSITE DIRECTION ( my ignorant self thought those were just some kind of transistor that looked like it was in a bad spot) :cry::cry:. I will look very closely at this later when I have time to delicately remove the motor coils for the second time. As for the coils themselves, I have 14.2 ohms on each coil installed on the board. Also I have the same worry about polarized caps at C12 and C14. Talk about a dope slap to the forehead. Best to leave some of these things to the professionals that know what they are doing like @SkywaveTDR . Or maybe I should look at the schematic before instinctually moving things around.........
 
Yes, The Hall effect devices provide a feedback to the driver chip. That is how the driver chip keeps in sequence. Usually those that do not know what they are doing buy this board as any good Technician would fix the old one with less trouble. it only take about $6.00 in parts. I do have a couple of motors that will require my attention to them down the road.
 
@gavin a keable , did you have a chance to bend those sensors in the correct direction and see if the motor driver works properly? Hopefully, the leads don't snap when bending them a second time. I am curious about your results.
 
I do not bend things placed in a certain place unless I know what they are and I did look for replacements but I am not sure they are easy to find. What would make anyone think that hall effect sensors could be placed in another position- don't they pick up a signal and their position is kind of critical I would think. Well I am waiting for some good news but I am afraid of what might be the result when the motor could have been repaired early on with less money spent. I repair them and I have never bought one of those boards as E bay is most certainly not the place to get complicated parts like this.
 
So here I am, Sam ;-)

I have this 122 MKII that was running like a jet. After having watched a video about how to replace the smd caps, I ordered the eBay capstan board as a backup before attempting to remove those smd caps myself.

The caps replacements was successful, but the motor was making some noise after a couple of hours and was going slower. So long story short, I received the new board, switched it successfully, but now, the motor is very slow until it stop. All the mechanical adjustments has been done by the manual. I also was able to calibrate the deck before it started to slow down.

After all the Internet reading and exchange on tapehead.org, I finally finished here asking your help.

I know you don't like these boards. I have probably read all your previous threads already lol...

You can have the full history with pretty good pictures on tapehead thread here:

http://www.tapeheads.net/showthread.php?t=95596&goto=newpost

I really do hope you could help me with all those deck already fixed. I thing I read once about 150 already done? Good job!!

My bests Regards,

Yves
 
Hi Yves,
The motors can be a headache to fix if they are badly damaged. I never tell people to buy the board on E bay as it is with the same garbage SMD parts that you have trouble with now. I only put in through hole parts that should last as long as the deck from this point forward. In my experience I test the motor and set the thrust point adjustment using a scope as connected to the FG test pin in the lower right corner. This is made maximum without clipping and that would be the nest position. I don't know what that new board has on it as I never buy that. Stability of the motor comes from two things- one is replacement of C2 which is a low grade ceramic and I put either a .01uFd Mylar or in the past the .001uFd Polystyrene. The stability and effect of humidity and temperature disappears. The next thing that has a major impact of motor is the il put in the capstan bearing. Some use 3 in one oil which is a waste product I think. I use AMSoil Signature synthetic oil 0W30 and I always get great results from that oil every time. Some motors are so damaged by leaking electrolyte that some foil patterns need to be patched with wire wrap wire. The ground foil along the edge is very common to be compromised. This job was with Polystyrene cap- upload_2022-3-16_8-31-20.png
 
Thank you Sam!

But as explained, I already did the recap upgrade on the old board and even if it has fixed the jet speed problem and had get back the motor speed to normal, after a couple of hour of playback or recording, it started to make more noise.

Than I received the new board and decided to proceed with the replacement. This board is almost exactly the same as the old one, to the exception that we must remove the motor coil plate and solder it back to the new board. This as gone pretty well in my case. To the exception that now, the speed is verrrry slow and after a couple of second it's stop by the hall effect wheel responsible to detect the end of the tape.

I measured -11.1 VDC and +11.1 VDC to the -12 and +12 VDC at the emitter of Q109 and Q110. So I am wondering if this low voltage could be the source of the new problem and if I should start thinking to recap the whole power supply?

From your answer above, would you suggest to recap anyway all the SMD and C2 of this new board, even if it is fresh new?
 
I have had no problems with 122 Mk III decks with regard to power supply except that some of the soldering in the audio section is pretty much as crappy as most others I see. Wave solder is fast but it is never aerospace grade. The capstan motor only gets 12 Vdc put to it. Why it is slowing I do not know as I never used that garbage E nay board and I suspect it is made in the same poor way with probably 20 year old SMD caps on there. I trust no SMD caps and I would never put them back on a deck like some guys do. SMD parts are made for throw away electronics which means 7 years according to the FTC. People do as they wish in a lot of cases but then they keep on sending me question about item I do not use like that board and do not follow my advice. I get results they might sometimes.
The hall effect and magnetic wheel is on the Mk II deck not the Mk III as this model used opto reflectors at the ends of the reel tables. On the Mk II I take take the reel tables off clean and libricate the shaft with oil the hall wheel gear connected to the right reel table is removed and clean and grease applied under the spring retainer after a good cleaning then oil is applied to the shaft and then the nylon washer and E clip goes on. If you take the brake off the reel table will spin much more free now and even though there is friction from the magnet wheel there is not the screeching noise present from plastic on metal shafts that happens when oil dries out- It happen on Technics decks too RS1700-RS1500 models.
In every case the C2 must be replaced by a better part- not doing so can ask for trouble. The Pitch control pot is also part of the circuit so this might also be considered as on 122 MkII deck many pots have broken inside which required me to come up with a better design using a 1 million operation plastic conductor pot instead of that 10,000 they used.
 
Thank you very much Sam for all your detailed answer! You have convinced me. At this point, I have nothing to loose. I will proceed with the recap of all the SMD and C2 caps on this new board. Seeing it is new with no traces oxidized yet, it should give me a pretty good deck for a long time.

As for the reel tables and all the cleaning you mentioned, I saw a video that explain all the dismantlement and lubrication of the unit. I wanted to replicate all the steps in the video but mine was so clean that I only did a brief cleanup with alcohol and a little silicone grease. I will proceed with all your suggestions, the deck deserve it.

Thanks again for sharing your experience, it is very well appreciate!
Sincerally
Yves
(Tube709 on Tapehead.net)
 
Hello Sam,
You said that you used recently 0,01uF Mylar capacitor for C2. Does Mylar Film Polyester are good for this? The green rectangular one? Or do you use other kind of Mylar caps?
 
I have used the Mylar .01 in a number of decks and it aides in making the unit more quiet as the cap is more a filter for a circuit as the reference is a voltage that you set and the voltage on the board is a little under 9 V due to the Zener diode that is near C2. I have had to measure that and in one case out of 140 motors I think I changed one but I never use SMD parts. This board is entirely capable of using through hole parts if they were to design it right but the SMD parts are cheaper and you know the result. I call those parts junk. So far even though I have stock on chips only one drive chip had to be changed- that is the big one at the top that this one was cracked and burned. IC3.
 
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Hum...

In fact my question is : does the Mylar capacitors you use for C2 are those rectangulars green one ?

I am trying to know the physical type you use. Would you have a picture by any chance ?
 
It all depends on who makes them but in general they look like this-
20175.Jpg
 
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