MCI JH110

[brianroth]

While I still think Jeep Harned was a brilliant businessman, he WAS a cheapskate sometimes.

Hence some terrible parts in MCI machinery.

Bri
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http://www.brianroth.com/

[ladewd]

You're right about that Brian, but Jeep did make his price point lower than the competition. We had over 200 PCB assemblers working there, labor was expensive so something had to be cheap.

airloom,

As far as cleaning the IC's, I use a pencil eraser and I rest the IC pins on the pads of my fingers to prevent them from bending. Clean from the top of the pin to the bottom. I clean both sides of the pins. Definitely change the op amp and logic IC on the PLL and torque boards (they're cheap). You may have some trouble finding all the IC's on the Lamp Driver board (depending on the vintage) except I would try and clean up those AD532's unless you can find them at a reasonable price. I seem to remember the later JH machines used AD532's with gold pins.

[sonicmook56]

A greenie worked great for me, to clean the funkey black shit off the IC pins. I don't think you need to replace them all!

~B

[airloom]

we cleaned most of the pins, but we managed to break some of them as well.
And I'll be damned if we didn't order the unsocketed TL081s when we needed them socketed.
Oh well. I don't pretend to know what I'm doing.
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[airloom]

Update for those who care:
We fixed our transport problem, thinking we were in the clear, then opened the channels and found more of those damned red sockets on the removable cards, and the ones below.
So, we're going to try and do this stuff over christmas, and maybe we'll lay down some killer guitar solos and post them.
We def. felt a feeling of accomplishment after the tape transport started working.
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[airloom]

Just for shits:
http://mcirecording.com/index.php

Picked up 2 parts machines last night
JH120/JH110T
AND
JH140/JH110T
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[dirtdog]

After a few weeks off we're visiting this monster in the living room again. We shotgunned all of the ICs and sockets and the transport seems to be rock solid in all speeds. Now we're having trouble trying to get our tape recorder to record.

Audio passes through when the channel is on Input. Nothing comes back when on Repro or Cue. Is there something obvious I'm missing that would prevent the signal from either getting to or returning from the heads? The head connectors on the rear of the electronics are connected.



Also: This machine came from a tv station and we're told that it was a JH-110A that was upgraded. We're running into a few inconsistent things (like I didn't think there were supposed to be these red sockets on an JH-110A but they're all over ours) that are making troubleshooting a little less streamlined than we thought. There is the white cylinderical transformer on the Repro cards which matches our 110A manual but the card also has two 2003M labeled can ICs on the board where the manual shows the 2001. The thought from an earlier post on this thread that the 110A used the 2001 and the 110B used the 2003/5534 (which are in ours on the Bias and Audio Motherboards). Were there a standard set of upgrades to the JH-110A that were frequently done or was it just as much as whatever someone felt like doing?

[dirtdog]

In repro, with the track armed, punching in and out doesn't change the hiss (loud) or faint echoes of what sounds like bulk-erased program material (quiet).

[airloom]

I wish one of the know it alls would come on and just say "oh yeah, just flip this hidden switch."
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[ladewd]

I have no magic switches for you. One thing to keep in mind, the inductance of the repro heads changed with the change from JH110A to JH110B. JH110A repro heads will not work on a JH110B and visa versa. I've never seen a JH110B with transformers that used 5534's (2003's). It is possible the machine was modified to use 5534's, since 2001's are not easy to find. If this is the case, you should see some cuts and jumpers on the repro board around these IC's. The power rail resistors needed to be increased to drop the power supply rails to +/-18v. IIRC, they were changed to about 560 ohms. Pin 1 needed to be cut and various other pins jumpered, but I don't remember the rest of the details.

I would suggest giving Steve Sadler at Blevins Audio a call. He has made a career out of supporting MCI products and I'm sure he remembers the details and history of these machines much better than I do. He charges for his tech assistance, but he's top notch and will help you get your machine running.

Cary

[airloom]

They've already been replaced with the 5534s.
I'll take a look at the rest of the stuff.
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[ladewd]

The point I was trying to make is that the 5534 is not a drop in replacement for a 2001. An unmodfied 110A will cook a 5534.

I don't remember the exact DC resistance of the heads either, but IIRC, the repro and record heads on a 110A have roughly the same resistance (a few ohms difference). On a 110B the resistance difference is much more significant. The repro head has a much higher resistance. You can check this stuff with an ohmeter. I don't know why ~70 ohms is sticking in my head for the repro head on a 110B. Its been way too long for me to remember details like that.

Good luck with it and if I remember anything else, I'll chime in.

[CurtZHP]

After watching this thread for a while, I'm starting to think I got off easy. My JH-110 (C -- I think) only has the dreaded red chip sockets on the Record cards in the audio drawer. Easy enough fix there. All the caps appear in good shape, as well as the heads, and the transport is very well behaved.

The only issue I appear to have is that she's a little noisy (tape hiss?). And you only notice this when there's little or no actual signal (which is why I'm thinking it's just tape hiss).

I've calibrated it as best as I could with an old alignment tape I have, and it appears O.K.
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[CurtZHP]

O.K. I spoke too soon.

While doing some other adjustments on the machine, I'm hearing a noticable hiss in the right channel when recording a 10kHz tone and listening to the output of the playback head (REPRO).

Otherwise, she's fine. Any thoughts?
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[airloom]