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+  MCI Console and Tape Machine Forum
|-+  MCI Tape Machines
| |-+  JH-16 and JH-24 (Moderator: Westrek)
| | |-+  My JH16, a life-journey...
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Author Topic: My JH16, a life-journey...  (Read 215 times)
rennywilson
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« on: June 05, 2017, 10:51:08 PM »

Disclaimer: I am posting in this thread simply because I heard this message board wasn't going away so quickly - since I can still log in, I can only assume the rest of you still can as well!
But alas, a lot of knowledge that was once here has potentially been flushed into oblivion for eternity - then again, I figure what better way to get that info we all need to share regarding the upkeep of these old machines (especially for a young schmuck like myself) than to spit it all back out there. I would also like to say that over the 4 years I've been a part of this message board I've learned so much reading through the posts of the plentiful experts who (used to?) lurk around here.

So as for my JH16

Well, I'll tell ya ppl she wasn't my first...

No, in fact; the JH16 that currently sits unassumingly in the middle of my living room is my second. I used to own the earlier "widebody" model (i think a 74") which is, would you believe it, in the basement of my house! (where the friend I sold it to keeps it)

My current machine is the 78" model with QUIOR, purchased from a fellow member of this forum. It had the audio cards recapped at some point in its recent history, but as I've poked around in the machine (and believe me, over the last year I've done a lot of poking... poking and prodding and accidentally breaking the... anyways  Lips sealed) I've found several old, original, dried-out capacitors, and a spattering of that who's cursed name shall not be spoken (red IC sockets), lots of grime, lots of dirt and dust... The devils advocate known as the many molex that plague these machines are brown, or grey with caked on dust and age (she's got a little bit of intermittence problems you know.) I've cleaned whichever I've come across a good scrubbing with q tips and isopropyl, and a little bit of contact spray in the fem-molex.

Suffice to say it's a bit of a wreck, but I feel like it does have the potential to be a great machine. It's failed on me for various reasons in the past, but I want to help usher my machine out of the darkness and into the light. I want to take it to all new heights. I figure at this point in my owning this (and my former) MCI machine(s) and having become much more confident in my electronics skills (although not too much more knowledgeable about the science of it) I'm ready to face the music - because as all of you older cats know (and have doom-sayed to the younger generation for at least a generation by now,) that is that analog is not a walk in the park. It's a devotion, and if I want this JH16 to be as good as it could be it needs that type of care.

Also, I would like to thank forum member Brian Roth for helping me out via email over the last couple of years. He's always been able to lead me on the right path towards being able to keep the machine afloat in times of need. Thanks Bri! This thread is an attempt to spread the request for knowledge around the MCI hivemind a little more, although Brian may feel free to add more to this convo should he so desire.  Grin

Without further ado, my MCI has the following issues:
  • VU's won't register on several tracks. I've tried checking the connections mounted on the meters themselves but for my channels 3, 14, and 15 I cant get anything (edit: since making this post i've lost VU16 as well. Dropping like flies here!)
  • windy audio on several tracks, this can result in slow drawn out movements in the meter, sometimes it will drift down completely off scale and then return (intermittent much?)
  • Godawful tape jitters, I'd tried some of michael blackmer's "mods" to fix these jitters, but ultimately those mods ended up rendering my machine catatonic for a while. They've been removed - fine modifications indeed. The Autolocator has been narrowed down as the source of the jitters (as it does not when set to the internal oscillator), the timer chip in the ALIII has been swapped, but the jitters continue
  • lmy rewind has seemed very sluggish in comparison to what it used to be, does the supply reel tension have anything to do with this? It's beyond slow, actually
  • Track 11 wont latch  into Rec mode and stay there without holding your finger on the record button. Swapping relays doesn't work. Perhaps cold solder on the Audio card motherboard is the culprit? this issue is very intermittent. It will latch on for periods of time (seemly random, though, I wanted to believe the problem was localized at the relay istelf), while latched it mayfall out of record moment at random, if that helps to give any indication
  • track  10 makes loud clicking thump when engaging and disengaging in record mode

The list goes on...

and aside from these quirks, I've just been overall pondering what could be done to overall improve the machine - I feel like I'm married to this particular machine in a way, and I'd like to try and "make it work" so to speak. It sure ain't perfect, but If I can't make it work then I don't think any analog multitrack would be right for me to swap this one with. I've been considering what It would take to redo all the molex connectors. I was reading through some old GS threads where Brian and Larry, and others, we're BS'ing about MCI machines - it was mentioned in there that someone they knew "did a hardware bypass" on every molex in their JH16, and although it could no longer be worked on it never needed work! The joke was a sham, though, as the aformentioned person who had done this mod eventually chimed in, stating that they replaced all the molex with gold (I'm assuming they are talking about a higher quality variety of molex connector). Is this a known modification? It sounds very involved, but a worthy side-step around the known intermittence issues.

And audio. This is a discrete, Xformered machine, loaded with tons of that analog tape mojo yadda yadda. None of that mojo is going away - I really want to get the audio path as clean as it can be in terms of headroom, and unwanted circuit related distortion. It would be amazing to hear some of the methods any of you might have used or even considered in an attempt to clean up the audio path on these units.

And where do you get lightbulbs for this damn thing? Is there a modern, more energy efficient counterpart I could swap in place?

(also thinking about taking this thing apart entierly so that it could have a custom paint job, but now im getting to ahead of myself - did i mention that this machine is cosmetically ugly as hell?)

I'll leave it at that for now,

THANKS Y'ALL
« Last Edit: June 09, 2017, 01:07:48 PM by rennywilson » Logged
rennywilson
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« Reply #1 on: June 08, 2017, 12:12:22 PM »

What's more responsive: a JH16 that just blew all its power transistors or this thread?

LOL, just trying to grease the gears here.

PS I'm going to start adding problems to the list above as they come up.

BUMP
« Last Edit: June 08, 2017, 02:25:17 PM by rennywilson » Logged
stageleft
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« Reply #2 on: June 12, 2017, 11:51:58 AM »

Happy to see this site hanging in there. Here's a Dropbox link to my collection of MCI info

https://www.dropbox.com/sh/dlsmqzt7tcq9e64/AACzMglGEQ1SZksuLzyNGzEoa?dl=0

Most valuable are hi res copies of the original JH416(A) schematics with the discrete modules.

Enjoy ...

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rennywilson
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« Reply #3 on: June 12, 2017, 01:23:56 PM »

Happy to see this site hanging in there. Here's a Dropbox link to my collection of MCI info

https://www.dropbox.com/sh/dlsmqzt7tcq9e64/AACzMglGEQ1SZksuLzyNGzEoa?dl=0

Most valuable are hi res copies of the original JH416(A) schematics with the discrete modules.

Enjoy ...

Thanks for this!

You get them from Corey, sweetbeats? Well if so they came from me! (I fedex'd my originals to him a few years back.)

FTR I own one of the Discreet 416a boards, very cool specimen.

UPDATE:

Through all my poking around in the machine this last week, I was able to get it working on 14 out of 16 tracks! this is a higher number than this tank has ever been able to manage. Not to mention, every  single  vu  meter WORKS all of a sudden, I cant tell what caused this but I feel like there's something to do with the red bias amp push buttons that are shorting the input signal from hitting the VUs. I am very happy about this, as this deck has never had a full compliment of working meters. Rewind tension is still a bit off, but the session ran without a hitch! I did notice some other issues of which I will add to my list, though.

But 3 cheers for my JH (which didn't transport tape/ sound very good a week ago)

 Grin
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Harrison
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« Reply #4 on: June 14, 2017, 08:54:09 AM »

re: AL3 jitters

I've put a reply back in yhe original thread
PC
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Harrison
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« Reply #5 on: June 14, 2017, 09:15:05 AM »

"My rewind has seemed very sluggish in comparison to what it used to be, does the supply reel tension have anything to do with this? It's beyond slow, actually."

Is it supply reel tension? No.

Have you ever resoldered the molex pins on the transport mother board? This is a known problem and requires the removal of the board and closely checking the pins vs pads on both sides. Pins crappy tin plating, joint with pad breaks down
Check that all power trannys in transport chimney are good.
Tensions are adjusted for play only; they have no bearing on any other mode.
How are the idles?

PC

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Harrison
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« Reply #6 on: June 15, 2017, 10:03:16 AM »

Track 11 won't latch  into Rec mode

The fault is on the strip board.  Record completion P7/7 grounds the record relay via the remote ready switch.
Momentary record P12/B puts 24v onto the relay via CR2. The relay is then self held in record via R6 (240R) and lights the record lamp. Q. Does the track record lamp light when you hold the record button down?

So either R6 is blown or solder pad breaking down around this, or the play 24v track from P12/A does not get to the relay socket.

I have seen broken/burnt tracks on these boards
PC
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