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MCI JH16 2" 16 Track - THE ROAD TO RESURRECTION 2k17 or how I became Steve's apostle
Old 3 weeks ago
  #91
Gear Head
 
S_mask's Avatar
 

You're right that LOW reads as if it should be a voltage.


However, the -110 manual I have shows pin 12 of J61 on its PLL board going to ground via a customary 0,39 R 2W resistor, so perhaps the posters were trying to say '... Volts should be measured 'across' MOTOR HI and LOW...'? That way you'd be O.K. not seeing any voltage on that pin. Is there very low resistance measured between it and ground? 'MOTOR HI' is often paired with 'MOTOR RETURN' on schemos, but op amps which drive such motors' HI or LOW pin (offering backwards drive) may well be given bi-polar supplies for which the terms 'HI' and 'LOW' are germane - not unlike signaling audio which is an alternating curent that has an Absolute electrical and, initially, and ultimately, acoustic polarity.



Fwiw, the -110 manual also states in its Troubleshooting section that for problems similar to what you describe, 'Adjust the Phase Locked loop gain control.'


Have you a manual for your JH14?

'Ere I am, J. H.'

(;
Old 3 weeks ago
  #92
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Brian M. Boykin's Avatar
I have a JH16 manual and a JH110 manual. My JH110 is functioning flawlessly so I’m testing against it now. Don’t know why I didn’t think of that before. I did follow the Hi and Low traces back to the op amps and the rails are switching. The -15 v is constant and the +22v switching with transport function. I’ll be testing against the JH110.
Old 3 weeks ago
  #93
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Brian M. Boykin's Avatar
Update: the +22v rail on the PLL board drops to roughly +8-9v when play is hit on the JH16. On the JH110 it does not. I’m gonna test the two 2n3055 transistors off R47. R47 is getting too hot to touch on the JH16 and it doesn’t even warm up on the JH110.
Old 3 weeks ago
  #94
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Brian M. Boykin's Avatar
It’s something on the PLL board. When it’s off the 22v rail reads fine. When it’s on the 22v rail drops below 9v and the transport takes a crap. I won’t be able to look at this for the next three days. Any ideas give me a shout. Till then.
Old 3 weeks ago
  #95
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Radardoug's Avatar
 

Not knowing the MCI imtimately in this area but based on how most motors work, High should be the supply volts for the motor, and low will vary with the speed regulation. 5 volts does seem low to me for the motor, its a d.c. motor but I would have thought it would have been 12 or 24 volts. Maybe a supply is gone, and 5 volts is creeping through from somewhere?
Old 3 weeks ago
  #96
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Brian M. Boykin's Avatar
Quote:
Originally Posted by Radardoug View Post
Not knowing the MCI imtimately in this area but based on how most motors work, High should be the supply volts for the motor, and low will vary with the speed regulation. 5 volts does seem low to me for the motor, its a d.c. motor but I would have thought it would have been 12 or 24 volts. Maybe a supply is gone, and 5 volts is creeping through from somewhere?
Agreed but the 5v is consistent with the JH110B I have. All the logic commands are initiated with 5v commands so maybe that’s all it is. I need to find out why the 22v rail drops under 9v in play. The JH110 does not do this. I’ll be digging into the manual and schematics over the next two days. Thanks for the insight.
Old 3 weeks ago
  #97
Gear Head
 
S_mask's Avatar
 

I checked my 110 (machine), and pin 12 of J61 is confirmed to be at ground potential. They show the 39 centi-Ohm resistor connecting the trace to ground in the drawing, but the pin is written as 'MOTOR LOW'. Whereas the DC motor's power terminals are wired like a simple light bulb, with the electron holes flowing (normally) from 'MOTOR HI' through the motor windings and out to Ground, so, MCI should have called the other terminal 'MOTOR RETURN'. '[MOTOR] LOW' implies a voltage 'lower' than the baseline 0 V, such as 'minus (something) Volts'.

The JH-114 uses the same capstan motor as the -110s, but with the longer shaft. Perhaps your JH14 does, as well.

When I was testing spares of these motors and adjusting the quadrature of the pulses from the tach, I only needed to supply about 2.5 V in order to get the thing spinning. Never needed to put more than about 3 V on it in order to see what I was looking for on the 'scope (...a 20-µs pulse train of unipolar squares).

I encourage you to test all the components on the PLL, but also carefully to cycle (again and again) all the Molex connectors and re-seat (again and again) not only all the boards, but also any socketed chips. Only partial removal of a chip from its socket is needed for the helpful effects of reinsertion that scrapes off signal-interfering oxide form the pins. De-Oxit is very effective on them, and if you have time to paint the socket holes, go ahead and fully remove each chip. Should last 6- 12 months before it needs another treatment, and sometimes can go much longer, if you use the machine often. HOWEVER, one must be very careful about reinserting the pins of a DIL chip, lest one of them gets bent under the package. It might look fine from above and yet not be correctly inserted.
Old 3 weeks ago
  #98
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Brian M. Boykin's Avatar
I’ve reset all the cards multiple times. All the molex solder points were reflowed approximately 2 month ago which is what originally fixed all issues and had the transport operating appropriately. Also, all red sockets have been replaced with machined sockets. This has been developmental. It started with just randomly slowing down and then speeding back up. Then progressed to just a slow speed and sometimes not coming on. This is over the course of 3 to 4 hrs of searching for the issue with short runs of running tape. My hunch is a connection or a failing/failed part. 741 op amps are so cheap I thought about ordering a bunch to just swap in and toss the old one. $30 for 100. I’d have spares for years to come.
Old 3 weeks ago
  #99
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Brian M. Boykin's Avatar
I had about an hour to play with this this evening. I think I may have found the problem. I moved to the logic board. Without going into super detail the FF, RW,Play, and Stop logic functions can be tested at P31 pins 1-5. Tape load, record, and others are pins 5-8. Anyway, they are +5v when tape is loaded in the tape photo cell. When you press a transport button the corresponding pin will drop to 0v thereby initiating FF,RW,Play etc... once let go the voltage returns to 5v. Well when play is pressed I see the 0v drop but stop also drops to 1.3v and stays there while the deck is trying to play. This means it’s trying to play and stop at the same time. The JH110 transport does not do this. Now to find the cause.
Old 3 weeks ago
  #100
Gear Maniac
 
2Low's Avatar
 

Quote:
Originally Posted by Brian M. Boykin View Post
This means it’s trying to play and stop at the same time.
I have seen this on my JH100 also ..occasionally
Both transport switches are on , Play and Stop
Hope you find a solution !


I´m working on the buss boards at the moment
There are mechanical / connection problems
One channel has dropouts when i move the drawer ( 1-8 )
Attached Thumbnails
MCI JH16 2" 16 Track - THE ROAD TO RESURRECTION 2k17 or how I became Steve's apostle-mci-jh100-bussboards.jpg  
Old 3 weeks ago
  #101
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Brian M. Boykin's Avatar
Quote:
Originally Posted by 2Low View Post
I have seen this on my JH100 also ..occasionally
Both transport switches are on , Play and Stop
Hope you find a solution !


I´m working on the buss boards at the moment
There are mechanical / connection problems
One channel has dropouts when i move the drawer ( 1-8 )
Exactly. In fact, the stop lamp will stay lit and the play lamp is flickering on and off. Monday I’ll be back at it. I’ll be checking connections and cleaning sockets. My JH110 did something similar and Steve helped me locate it. A bad stop switch. The deck was stuck in stop. May be a similar issue.
Old 3 weeks ago
  #102
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2Low's Avatar
 

I´m trying to adjust the VU meters on my JH16/100 machine
before any other serious level adjustments
and found out that the balanced signal is „unbalanced“

I send a perfect balanced 0db ( 1,228 V ) in
and get f.x. 1,425 V and 0,205 V on pin 2 + 3 on the XLR outputs
Its the same on all channels

Does anybody know where / how to adjust it ?

Thanks !!!

Unfortunately i still haven't found a manual for the machine ...
Old 3 weeks ago
  #103
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Your post is confusing. Do you mean that you measure 1.425v between pin 2 and ground and .205v between pin 3 and ground?

The outputs were originally fitted with transformers so that might not be relevant. If you think the outputs are unbalanced, look at the transformers to see if they have been bypassed or jumpered. Or maybe something in your cabling or signal flow is causing the outputs to be unbalanced. You can check for this by looking for a low resistance between ground and pin 3 with everything powered down.

The VU meters are calibrated by feeding an oscillator signal into the input and adjusting it so that 1.23v is seen on the output XLR with an external meter that is known to be accurate. Then adjust the small trimmer on the VU board to make the machine meter read zero VU.
Old 3 weeks ago
  #104
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2Low's Avatar
 

Quote:
Originally Posted by David Kulka View Post
Your post is confusing. Do you mean that you measure 1.425v between pin 2 and ground and .205v between pin 3 and ground?

Sorry ..my english is bad
but: Yes

Quote:
Originally Posted by David Kulka View Post
The outputs were originally fitted with transformers so that might not be relevant. If you think the outputs are unbalanced, look at the transformers to see if they have been bypassed or jumpered.
I don´t think so, no mods, all transformers in place

Quote:
Originally Posted by David Kulka View Post
The VU meters are calibrated by feeding an oscillator signal into the input and adjusting it so that 1.23v is seen on the output XLR with an external meter that is known to be accurate. Then adjust the small trimmer on the VU board to make the machine meter read zero VU.
I send an 1Khz - balanced 1,23v signal from an Pro Tools output , measured the volts

The signal in front of the MCI XLR Inputs is 1,23V on both sides
The outputs on the MCI´s XLR is something like 1.425v between pin 2 and ground and .205v between pin 3 and ground

Thanks David !
I will do it from scratch tomorrow
Old 3 weeks ago
  #105
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Because the machine has transformers on the outputs, the voltages between 2 / 3 and ground are not really of interest. Those voltages will be random and don't mean anything because the outputs are floating, with no true ground reference.

Make your measurements between 2 and 3, and ignore ground.
Old 3 weeks ago
  #106
Gear Maniac
 
2Low's Avatar
 

Thanks !!

whats the right value between pin 2 /3 ?
Old 3 weeks ago
  #107
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...

Quote:
Originally Posted by David Kulka View Post
The VU meters are calibrated by feeding an oscillator signal into the input and adjusting it so that 1.23v is seen on the output XLR...
Old 3 weeks ago
  #108
Gear Maniac
 
2Low's Avatar
 

Old 3 weeks ago
  #109
Cheers to you fine gentlemen. This thread makes me feel even more grateful I found a tech local to work on my Tascam 32,38. More power to you guys.
Old 1 week ago
  #110
Gear Maniac
 
2Low's Avatar
 

Tape Tension Question for the JH16 specialists :

I adjusted my transport according to the instructions in the manual
Good readings for tension ( " fish scale method " 6 oz + 12o z ), Idle, Offset null etc.

I read very often :
" For take up tension, just push the pinch roller away from the capstan and adjust the tension so that the speed does not vary significantly "

This doesn´t work on my machine ( JH100 non Quior - no dancer arm ! )
The tape slows down and stops .. what to do ?

Reduce the Supply Reel tension or increase the Take Up Reel tension ?
With the same amount of tape on both reels or for Full Reel / Empty Reel individualy ?

thanks
Old 1 week ago
  #111
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Quote:
Originally Posted by 2Low View Post
...Reduce the Supply Reel tension or increase the Take Up Reel tension?
Maybe a little bit of both. But also, make sure that nothing in the tape path or deck is creating friction (tape rubbing, sticky brake, etc.)

Don't expect that tape will move at 15 or 30 ips with no pinch roller contact...that's wishing for too much. Just be sure that if you give the the take up reel a gentle spin, the tape will at least keep moving forward for several seconds from the momentum of the reels and isn't being held back.

You might need a Tentelometer to verify correct tensions in play mode. Otherwise, unless you have enough experience to adjust it by feel, I'm not sure how you could do it properly. The "free wheel" method will help you make sure that the tensions aren't interfering with tape speed (differential in tension between the two motors), but that doesn't mean that tension across the heads is really correct in play mode.

Last edited by David Kulka; 1 week ago at 05:14 PM..
Old 1 week ago
  #112
Here for the gear
MCI analog torque board

Does anyone have a spare analog torque board for a JH110?
Old 1 week ago
  #113
Gear Maniac
 
2Low's Avatar
 

Quote:
Originally Posted by Eddybopp View Post
Does anyone have a spare analog torque board for a JH110?


Talk to David
https://studioelectronics.biz

or Randy
http://www.blevinsaudio.net/main.htm
Old 1 week ago
  #114
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Brian M. Boykin's Avatar
Quote:
Originally Posted by Eddybopp View Post
Does anyone have a spare analog torque board for a JH110?
Because yours took a crap or you need one for rebuild?
Old 1 week ago
  #115
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Quote:
Originally Posted by Brian M. Boykin View Post
Because yours took a crap or you need one for rebuild?
replacement, board burned after a short out.
Old 1 week ago
  #116
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Brian M. Boykin's Avatar
Quote:
Originally Posted by Eddybopp View Post
replacement, board burned after a short out.
It’s unable to be repaired? In any case, try the sources 2Low suggested and watch EBay and Reverb like a hawk. I see JH110 parts coming up daily but they go fast if they’re priced to move.
Old 1 day ago
  #117
Gear Maniac
 
2Low's Avatar
 

Does anybody know how to adjust the height of the Impedence Roller on a JH 100 ?

My Transport looks pretty good , but this roller needs a little adjustment ..

Thanks !
Attached Thumbnails
MCI JH16 2" 16 Track - THE ROAD TO RESURRECTION 2k17 or how I became Steve's apostle-zroller.jpg   MCI JH16 2" 16 Track - THE ROAD TO RESURRECTION 2k17 or how I became Steve's apostle-bildschirmfoto-2020-01-27-um-21.42.33.jpg  
Old 16 hours ago
  #118
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MCI / Sony used to sell machined alignment blocks that could be used to check tape path height but in truth they were not a great solution for this. (Among other issues, the coating of paint on the deck plate will never be perfectly even.) The best thing is really to carefully inspect the tape path by eye under a bright light. Make sure the tape is centered across all the guides and heads and forms perfectly smooth planes between the various components with no wrinkles or ripples in play mode. This is a tricky process that can be affected by height, wear patterns, and zenith in all the guides and rollers, capstan azimuth, condition and alignment of all the heads, reel motor height, etc. You can simplify things a little initially by putting the machine in MVC mode or putting it into play with the pinch roller held back and spinning the take up reel by hand, which lets you check tape path with the capstan motor out of the picture.

Since gravity will always pull the tape down to some degree, the capstan motor is normally shimmed by a tiny amount to slightly to pull the tape upward and counteract that.

2low, if everything looks good in your tape path except for the roller in your photo, re-shim it for smoothest tape path.
Old 13 hours ago
  #119
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crosscutred's Avatar
Quote:
Originally Posted by 2Low View Post
Does anybody know how to adjust the height of the Impedence Roller on a JH 100 ?

My Transport looks pretty good , but this roller needs a little adjustment ..

Thanks !
It might be worth considering if the height of the supply reel is the possible culprit.

Are the fixings holding the reel motor all tight?
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