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[Shawn Sullivan]

OK.......also a very strange development (at least to me and I know nothing) the left motor is running clockwise while the right motor is running counter clockwise! this would rip a tape up pretty good.  I tried un-soldering the brown wire off the rewind button but it still does the same thing. Apparently thats not the problem  (or I unsoldered the wrong wire, or there is another problem) ................Help!

Thanks again guys!

[robk]

Shawn Sullivan wrote on Wed, 24 November 2004 07:15

OK.......also a very strange development (at least to me and I know nothing) the left motor is running clockwise while the right motor is running counter clockwise! this would rip a tape up pretty good.

Well I'm no expert, and don't know that machine - but on machines I had years back that's the way the reels would spin when in 'play' to maintain tape tension  ...and as the lifters don't lift, sounds like yours might be stuck in play?

I recall that on Tascam machines we had, if you pushed the lifters in by hand with no tape loaded, the reels would spin up as you describe - so maybe there's a mechanical or electrical problem with the lifters, and the reel motors are just doing what the lifters are telling them?

Rob
www.visibleform.co.uk

[trexrox]

Can you spot the tape end sensor?  It's between the capstan and the right roller guide...  Make sure the path through that sensor is clean and free of debris.  

There is a function to make the reels spin (albeit, at a very slow speed) when tape is merely threaded.  This is to provide a small, constant tension on the tape.  If adjusted wrongly this can make the reel motors run too fast... There is an adjustment for both left and right idle tension on the Analog Torque Board.  You may want to get out the manual and go through the procedure of adjusting the idle tensions to see if it changes anything here...

[John Klett]

When you turn on a JH-24 with no tape on it the transport should be inert.  No button pushes will do anything.  The transport has to know tape is threaded in order to do anything.  

There is a tape sensor on the right side of the deck.  This is a small rectangular object mounted on the deck that has a slot in the top that the tape would pass through when properly threaded up.  This is an optical "tape break" sensor.  

Normally if you drop something opaque into that slot you will hear a click (the breaks coming off) and the reel motors would turn slowly - the left one clockwise and the right one counterclockwise.  The turn rate should be something like one turn every two or three seconds (not what you are experiencing I take it).  In this state one could grab either reel hub or both and stop the rotation.  

Turns rate is really determined by the amount of current flowing through the motors.  Current determines torque and the torque (rotational force) translates to tape tension (a linear force) which for a given torque will be greater with a shorter radius (less tape on the reel) and less with a larger radius (more tape on the reel).  

In play and wind modes - if you don't have tape on the machine and are simply testing modes with something blocking the tape break sensor the reel hubs will turn fast.  In wind mode the reel that would be picking up tape will turn faster as it is getting the most current...  the feeding reel has to have sufficient torque to produce enough hold back tension to produce a decent tape pack.

So...  If both your reel hubs are turning fast as soon as the machine turns on and assuming you measured your MDA transistors properly you need to step through a couple things.  Are the breaks turning off?  This may be hard to determine but if there are not turning off you would hear them rubbing.  Do the mode switches light up at all?  Do they change status when you push buttons?  Does the pinch roller pull up against the capstan on power up?  Does the capstan turn on power up?  

The way I see this is that the machine could have some sort of logic problem or other component failure that is telling the motors to spin.  This could be something caused by interconnection issues in the machine - not uncommon.  

With the power off --- you can flip down the front panel over the audio drawers and find two quarter turn latches that, when unlatched, will let the transport swing up.  With the transport flipped up you can see all the deck controlling boards.  There is a motherboard and a number of daughterboards mounted to it on pins that stick up from the motherboard through connectors on the daughterboards. Those pins and the mating connectors are made by Molex.  Molex connectors are not bad in themselves but the ones in MCI machines cause a lot of grief and have done so since them machines were fairly new.  MCI = Many Contacts Intermittent.

If both reels are turning and you checked the MDA's then another thing to do is try moving the daughterboards, carefully, up and down on the pins they mate to.  If anything about your deck issues change after giving it the "Molex Wiggle" you may have to invest some time into cleaning up the pins (not with an abrasive and not by "re-tinning" them with solder - that permanently ruins the pins and often the mating connects as well - you would have to replace them if that was done).  Very often a simple exercising of the boards up and down on the pins will clear problems.

Another Molex pin issue is that the solder connections may have cracked.  On thing I did when rebuilding these machines was pull the motherboard out and retouch ALL the solder joints for all the Molex pins.  That ALWAYS helped make the machine more solid and reliable.

There are other connector issues - MCI bought a big load of IC sockets from Aries.  I've used other Aries stuff and had no problems but those RED Aries IC sockets were really awful and caused a lot of problems.  If there are red IC sockets those should go away and be replaced by something new and better.

So - connection issues are one possible cause so before you start trying to trouble shoot logic and commands you should make sure it isn't something mechanical.  Also you should check to make sure your power supply voltages are where they should be.  I don't have a book here and I don't work on MCI machines much any more but someone here should be able to tell you where and what to look for

After you have gotten through connectors and power supply you have to start looking at logic and commands... You would ideally need to have a 'scope and the book for the machine so you can walk through the thing...  are the reels being told to turn...  does the logic latch into a particular mode?  is a chip blown?  are command lines latched or shorted...  and so on...  it's a process.  A tech who has worked on MCI and knows how to get around in the book should be able to figure this out in an hour or less (once he has his tools out and the scope warmed up) at least to the point where parts can be ordered.



Here is a general comment - someone else expressed something like this here recently...  

A lot of people with no technical chops are buying used gear.  The prices are very low and it looks like a good deal.  This gear is old and used and always needs work.  Plug and play does not happen with this equipment.  You pretty much have to be prepared to buy some tools and test equipment and learn some basic electronics and troubleshooting skills if you want to own it.  You can get a lot of help from the community here but any used large gear like tape machines and consoles that you can't simply send out to someone else to fix is going to be yours to deal with.  Hiring a tech is expensive and beyond the budget of a lot of people.  We are dealing with the same things people who buy and restore old cars deal with except we often buy this stuff to use for primary transportation right away.  THAT is not realistic.


Generally...  you must make all efforts to get a complete manual with schematics and technical descriptions.  You have to budget time and money to get the equipment into good enough shape to use...  at today's prices for used gear and keeping in mind that the prices of parts and technical expertise is probably more today than when the equipment was new you should figure that what ever you paid - you will pay that much again to make it work for you (and not against you)

beyond that...  I'll start a topic.



see if you can do the Molex wiggle and characterize what is happening with the brakes and other indications of "mode", pinch etc.  All this will help people here help you figure this out

[xonlocust]

hey shawn -
[non tech advice here] there's been a lot of great advice by people much smarter than i - but in addition you might bookmark this link for some resources - http://groups.yahoo.com/group/sony_apr/ there are a bunch of recent posts about "new mci user advice" that you may find useful, covering a lot of the usual suspects (red socket ICs/molex etc).  by no means am i suggesting any advice here isn't good, i;m just offering more resources for you.  good luck w/it and back to the techs who know what they're talking about...
nick

[Fig]

Shawn Sullivan wrote on Wed, 24 November 2004 01:15

OK.......also a very strange development (at least to me and I know nothing) the left motor is running clockwise while the right motor is running counter clockwise! this would rip a tape up pretty good.

The reverse directions are for tension.  If there was really a tape on there, it would probably be fine.

I agree that it sounds like you are stuck in play.

After you have located the tape sensor, check to see if the bulb is lit?  Its photo optic, right?

I've never had that problem with the MCI, but the old 3M M79 I grew up on had a bulb in plain view that went out once.  

Machine thinks there is tape.

Good luck, I sympathize with your plight.

Furthermore, I agree 100% with John's comments about picking up old gear and think that it SHOULD be its own thread.

John?????

I have spent almost as much after the purchase of old gear on spare parts, new tools, documents (which can cost a fortune!!), training (from an experienced tech) and/or technical services for things beyond my ability.  I have a new mantra -- labor of love, labor of love, labor of love.

It keeps me from taking a hammer to it!

Regards,

Fig  

[Shawn Sullivan]

Thanks John! I figured this would be a nightmare going in (back into a analog deck) and assumed it would cost quite a bit of money and time to keep a machine running and maintained the way I want it to.

Let me answer a couple of questions. The pinch roller does not "pinch" but the capstan is working. The left and right reels spin very fast and hard away from each other. There doesnt seem to be any drag or braking happening that I can hear. Just smooth spinning.  None of the transport lights are on and the machine does not respond to any transport controls. Beyond this I will try reseating the molex connectors and touching up solder points there. I would like to check the photo sensor but dont know how. (i will blow it out as someone else suggested)

Is the photo sensor supposed to light up? beacuse it is dark now.

[Shawn Sullivan]

Thanks!

[John Klett]

The tape break is an LED based opto and when it doesn't work the machine won't go - I have seen them fail on the opto side but not on the LED side...  but it's possible...  the is a sensor sensitivity adjust under the deck.  I don't think it's the sensor AND being jammed into play - that's two problems consipring together.  One is low probablility.  Molexia is the prime suspect and has to be eliminated.

[Shawn Sullivan]

I am very interested in replaceing the molex (since its officially a nightmare to all) with gold plated molex. Are these gold plated connectors available? is it worth it in your opinions? Where can I find them?

I will still trouble shoot the existing to the best of my ability of course.

[John Klett]

Shawn Sullivan wrote on Wed, 24 November 2004 15:28

I am very interested in replaceing the molex (since its officially a nightmare to all) with gold plated molex. Are these gold plated connectors available? is it worth it in your opinions? Where can I find them?

I know a tech - well - a long time ago - I knew a tech at LA Studios (Caheunga) named Kieth S...  can't spell the last name...  cool guy.  Anyway he did that exact upgrade.  Molex had the parts in gold although the females that mounted on the cards did not come with gold mounted in the shells so the original pins had to be slid out and the new gold ones inserted.  It worked well.  This was maybe 15 years ago but Molex has not changed that line of connectors in ages so I imagine that you can still do this.

[Shawn Sullivan]

Here are some pictures of the boards, including one apparently missing an IC.  The part number of the IC's above and below this missing slot are

Texas instruments
618 D B
SN75454BP

Also there is (as you can see) a 90 pin ELCO connector located next to the right motor which seems to be a mod to mate up with the other 90 pin ELCO for the remote. On the remote side there is several wires hanging free (red with black stripe, red w/yellow stripe,  green w/white stripe and lastly solid white)  Of course I have no idea if these were used and just broke off or if they are unused wires for the remote. There are no E-pins lurking around in the connector so it appears that they were unused but I could be dead wrong. One last thing. IC 's 22 and 23 on the analog torque board  (part number below)

AC
TL081 CP

have a black tar looking material on the side of the pins. I pulled them out and reseated them to check it out and they appear a bit corroded compared to all other IC 's I have seen on the board. I was wondering if this was normal.

[Shawn Sullivan]

Here is the 90 pin elco near the right motor (remote mod?

[Shawn Sullivan]

Analog torque board IC's 22 and 23 have black tar like subtance on the sides of the pins.

[Shawn Sullivan]

here is the other 90 pin ELCO on the remote side, presumably to mate with the ELCO inside the machine ( the machine ELCO tail reaches barely to the back of the machine though)  What a cluster! Any ideas on all this info? (besides hire a good tech... which I'll probably have to do anyways)