otari mtr-90 mkIII transport issues

[digitall2000]

hi all,

having an issue with an otari mrt-90 mkIII, have been using this paper by j. s. smullian to do the transport alignment

https://drive.google.com/file/d/1mST1sGW-5zzIR_jM0RNffXoJjNMAfJ_T/view?sp=sharing

could someone look at this and tell if it is a good reference, used it a while ago and the machine worked well for a while but this issue keeps coming back some sorta ghost in the machine.  or if someone has a better alignment procedure maybe they could enlighten me with it.  the owner wants to use GP9

or any settings, tensions, voltages that may help.
this closed loop servo system is a b!^@h when it's outta whack

the problem is now two fold

1. the machine won't ffwd/rwnd with out "unloading", i say it that way because the button on the far left of the transport control strip at the front of the machine is called "unload button" and this action exactly emulates that, so shortly after initiating  ffwd/rwnd the tape unloads, tape goes slack, brakes kick in and sometimes keep things in proper order, sometimes the tape pack is a mess and can't even run in cue mode at full tilt.

2. all of a sudden the tape position counter doesn't work, don't know if these two are related, but i don't think so because we had the same issue  with the "unloading" before tape counter issue cropped up

so some more history
had this machine working for a little while about 6 months ago and my client was using it to fly tracks in and out of protools and it was working great, sounding great, then all of a sudden it starts acting up again, but this time i notice a slight tick coming from the capstan motor, so in talking to soren he had me send him pics of the capstan motor voltage rail, it was flat-lining at 40v and spiking erratically
so we sent the capstan assembly to soren at cs electronics

CS Electronics
Soren Wittrup
461 W 400 N
Valparaiso, IN. 46385
U.S.A.
ph.: 1 773 562 3527
email: [email protected]

soren disassembled the motor, sent us pictures, the motor was pretty much fried, he  acquired the exact capstan motor from a guy in sweden for @ $200 and attached it to our existing capstan assembly for what i consider a great price and did a great job
the guy in sweden still has some of these motors (tradera.com, ebay.com) if some one needs one afaik.

so on this last pass when getting the motor back from soren i put it in and fired up the machine and it still did not ffwd/rwnd but would play fine so i started on the j.s.smulian setup when i got to the end of page 4 paragraph 5: "this completes the adjustments on the REEL CONTROL card."  i tried the machine and got 3-4 successful ffwd/rwnd runs so decided to move on, that is when things went south again
no ffwr/rwnd again.  also noticed a difference in the capstan tacho board out put

https://drive.google.com/file/d/1m51nNx4BclNKeWzHWF2mF2IHy4uj4xPV/view?usp=sharing
https://drive.google.com/file/d/18859b9IKrMKBq5HA2X8RZWwKxcUAcsqg/view?usp=sharing

so if you look at these pdf's
the top of the sine wave on channel 2 (green) output is chopped off slightly
also on that same signal, channel 2 square wave output, the square wave output goes below
zero volts, don't know if that would affect the logic involved or not, here are the specs.

sine wave
tp101 pk-pk 8.0V ch1
tp201 pk-pk 9.57V ch2
tp 201 is clipped slightly but phase looks goo to me

square wave
tp201  pk-pk 5.02V
tp202  pk-pk 9.57V
min voltage on pt202 drops below 0V whereas tp102 does not

any ideas
thank you in advance
lance

 

[radardoug]

Hmm, crossposting on two forums! See my reply on gearslutz.

 

[digitall2000]

if that is wrong i apologize, but i'm sure every one is not on both
forums and in my experience so far there are only a hand full of
people that really know these machines

i live and this studio is in the central san joaquin  in california
hell  we don't even have a electronic parts store as the last one shut
down 3 months ago and that is in a city of over 500,000, it has always
been kinda a backasswards over sized farm town
so i am grasping at straws here

thanks for your input, it is greatly appreciated
lance

 

[digitall2000]

maybe i ask too many questions

so i would like to solve an issue with the tape position counter
as in neither the one on the machine or the remote work
nothing but zeros, this is new

we got new rollers and springs from athan corp replaced bearings
so all the mechanical issues should be eliminated
athan tested the capstan assembly and said it was in solid working order
https://www.athan.com/store/c19/Otari_MTR-90.html

where is the tape counter card?  is that the small card on the left side roller assembly?
very hard to see
does the machine use the left hand tacho information as par of the transport function?
could it malfunctioning cause a problem like this?

the left side roller assembly is a shadow plate and some sort of photo/sensor assembly
t​he only numbers on it is "N 17k"
does anyone know of a replacement​​?
does anyone know what the output should look like?​

​thanks again for your insight
lance​

 

[digitall2000]

there are no instabilities in the transport, no jiggly swing arms or weird
tape path issues the machine just unloads
we have replaced most of the tape path mechanical system

so last night while researching i saw a reel motor out of the machine
the reel motors also have a "shadow plate"/ir opto sensors
so there are four of these sensor assemblies and this triggered
a memory of something from 25 years ago

1. capstan with two sensors 90 deg out of phase to tell speed and direction
correct or not?

2. left hand idler roller, i take it that is the tape counter part of the system
and is different from the others
correct or not?

3. the two reel motors have yet a different shadow plate/sensor assembly
even though they are different from the others, they are both the same

so don't at least the capstan and reel sensor assemblies need to stay in step
and if any one of these doesn't create a good logic pulse or "hiccups" then the
transport system would "unload" ?

this happened to a 16 track machine in a studio i was working in 25 years ago
we spent a lot of money on two techs and on taking it to the factory rep in
los angeles who fixed it, but on getting it home again they actually did not fix it
until we found a local tech, who won't work on tape machine any more
who knew what the problem was after watching the machine for  five minutes
he traced it down to one of the opto sensors $1 part fixed it

any ideas
thanks
lance