The MCI JH 16 (later series with the JH 114 transport) and all JH24 machines plus the JH110 machines
all come with basically the same Transport Card. That's a great thing, since this
means there is basically ONE alignment you need to do no matter which MCI machine you have!!
There ARE DIFFERENCES - various resistors have different values in order to give the sufficent voltages
and current to the motors for various tape widths. But if you look at a JH 110B Transport card
it looks EXACTLY like a JH24 transport card! Very difficult - almost impossible to tell the difference!
So here's how I align a MCI transport card - in this example I'll be talking about a 2 inch machine.
Step 1): Turn OFF the machine, and gently grasp the edges of the transport card and remove it
from the machine. Using LPS1 or your favorite spray cleaner, spray ALL the molex recepticles.
Re-insert the Transport card gently. One of the great faults that MCI made was allowing the card to
be able to be re-inserted one pin off from the correct position - damaging the card once power
is applied... so make SURE that you've installed the card correctly BEFORE turning power back on!!!!
Tip - I look at the lower 3 pin connections to make sure I've mated the card to the pins correctly.
2nd Tip - some of the Molex connections are NOT fully pinned! That is they are missing a pin, so this
can fool you! Be VERY VERY CAREFUL. Double-check that you've got it in correctly !!!
Step 2):
Next the most important thing is to insure that the Motor connections are good.
Go to the rear of the machine (it's still OFF), find the Molex connector that goes to one of the
reel motors (a 2 pin molex as I recall...) and spray clean this connector for EACH reel motor!
Step 3): Next find the wire that goes from the Reel Motor Tach (which is mounted just below the motor) and follow
that wire down to the molex connector that goes into the large Mother Board. Pull the connector
away from the mother board and spray clean it, then re-insert it.... double checking your connections !!!
Do this for each Reel Motor Tach.
Step 4): Open up the Transport Power Supply.
Take out the Driver Card and visually check for cold solder joints at the Molex Pins. If you
even suspect one, resolder it. IF the card has the 'dreaded Red Sockets', you MUST replace them now!
Check the resistance of EACH high power resistor. These are usually .39 ohms so will almost measure
as a short. If you find one that is open - i.e. a high value, replace it and test all the motor drive
transistors !!!
Step 5): It is ESSENTIAL that ALL your Power Supply fans are working in top condition.
If they are still Original, they're going to go bad soon, so replace them. This is the cheapest
insurance policy you can have in keeping your MCI running well, so check your fans often !!!
Step 5): It is ESSENTIAL that the +15 volt and -15 volt power to the transport card
be within .2 volts or closer... check the voltages on the card, and if there is more than
a .2 volt difference between the Positive and Negative basic 15 volt voltages -
say one is +14.9 and the other -15.6 volts you MUST change the voltage regulators
at the back of the Transport Power Supply.
NOTE: These are 340-15 and 320-15 and/or 7815 and 7915 regulators... cheap and easy to purchase.
NOTE: There is about 20 volts on one of the Regulator cases! Make SURE to replace
the plastic cover over each of the Regulators - or if you've lost them, use electrical tape
and cover the body of each regulator IC. !!!
Since you must set the Reel Tach Null to 'Zero volts' with no reel movement,
which is the exact mid-point voltage between +15 and -15 volts,
you need the proper rail voltages. If the voltages are off
then the DC Null has to be set at something other than zero, which isn't correct and makes the
transport alignment difficult or impossible to do easily.
If you cannot set the Reel Tach Null to Zero volts
and have checked that your +/- 15 volts are correct, and the reels are not moving,
then you should replace the 3 LM741cn IC's #4 and #10 and #11.
Step 7):yet to be finished !!!
Step 8):yet to be finished !!!
The dreaded RED SOCKETS of MCI
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MCI Power Supplies
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