New to me MCI JH24 - stupid annoying problem

seankerns

Member
I picked and '82 JH24 up locally, ostensibly to do transfers, but I like it enough, I may try to do some recording on it.

It's like, 95% perfect, but it has an annoying habit it seems to have developed after I had it for a few days.

I'm not a tape machine tech. Nor do I know any local to me "Cinci". I'm techie enough to work on my own guitar amps and do all my own guitar setups, wiring, neck adjustments, and so forth, and I manage to keep most of my reel to reel and cassette decks running. And I soldered up all six harnesses to get signal in and out of this thing. Whew.

I was fortunate enough to get the big, 3-ring binderized manual and a "Standard Tape Labs" 15IPS calibration, and even has the logic annunciator board with it (which was actually lost inside the cabinet). Anyway, on to the problem. Again, after having it for about a week getting to know it, calibrating for playback, etc., what it's started to do is that when I hit play, the light on the switch lights up, but the tape doesn't move - UNTIL, and this took me some time to figure out - I rock the feed reel clockwise just a smidge, essentially I guess putting a little more tension on the tape.
This seems like something that should be an easy adjustment somewhere. On the logic annunciator board, the light showing "play" was pressed lights up, but the two showing signal to the left and right motors don't light up, until I rock that left reel.
I've been trying to work out what it is I'm affecting when I do that, because it seems like the answer is in there, somewhere.
Again, I have the manual, but the troubleshooting basically says stuff like, "Check IC___". Yeah. No.

Aside from this, the machine plays and records beautifully.

This seems like something that would be pretty common to these machines, so I'm hoping someone else has run into it and can point me in the right direction. I can see that the machine has had lots of maintenance over the years. The dreaded red IC sockets I've read about have been replaced, and I see lots of "newer than '82" caps and IC's in the thing. I got it from the second owner, who himself had it for over thirty years, and both this machine and his studio in general look like he generally too care of his gear.

Thanks in advance,

Sean
 
Greetings, Sean!

So when you hit PLAY do the reels jump a little and then nothing else happens?
 
Greetings, Sean!

So when you hit PLAY do the reels jump a little and then nothing else happens?


I hear a "thunk", and the reels move just a little, then nothing till I rock that feed side reel. I can video the phenomenon if it helps. Thanks, Cory!
 
And BTW, in replacing the burned out VU meter bulbs, I just learned why it's a bad idea to do that with the power on. Does anyone know where the fuse is which controls all the lights on the meter bridge? I've been pulling and testing the ones accessible from the back of the machine on the power supplies, and haven't found it yet.
 
Does the pinch roller engage quickly to the capstan? It should be a crisp action when you hit play.

A video might help.

The proper response is to go through the transport adjustments and setup as laid out in the manual. That will likely reveal the culprit or or culprits to your issue, but making sure the pinch roller snaps into place is one thing, and then the other is related to holdback tension. If the tape is getting slack on the supply side then either the capstan is not driving pulling the tape like it should as quickly as it should, or the supply reel holdback tension is off. This can be resulting from too low a tension when PLAY is engaged, or delayed holdback tension engagement. I don't know how sophisticated the servo system is on the JH24, but they can be fairly complex in order to achieve rapid tape speed stability and gentle tape handling. I'd be refering to the section of the manual that walks you through checking out and setting up the transport adjustments. Another thought...if the machine has physical brake assemblies, chacking to make sure those are releasing promptly when PLAY is engaged.
 
I'll get a video of it here in just a minute and post it. That's probably the easiest way to demo it. Thanks, Cory.
 
Does the pinch roller engage quickly to the capstan? It should be a crisp action when you hit play.

A video might help.

The proper response is to go through the transport adjustments and setup as laid out in the manual. That will likely reveal the culprit or or culprits to your issue, but making sure the pinch roller snaps into place is one thing, and then the other is related to holdback tension. If the tape is getting slack on the supply side then either the capstan is not driving pulling the tape like it should as quickly as it should, or the supply reel holdback tension is off. This can be resulting from too low a tension when PLAY is engaged, or delayed holdback tension engagement. I don't know how sophisticated the servo system is on the JH24, but they can be fairly complex in order to achieve rapid tape speed stability and gentle tape handling. I'd be refering to the section of the manual that walks you through checking out and setting up the transport adjustments. Another thought...if the machine has physical brake assemblies, chacking to make sure those are releasing promptly when PLAY is engaged.

Cory,

Here's a vid.

YouTube

Still need to find what powers the lights on the meter bridge. Seems like that comes off the connectors from the ALIII, but I don't know where it comes from originally.
 
Your video doesn't allow me to see the whole tape path when you hit PLAY. I need to see supply side to takeup side when you are engaging PLAY. Also, it would help if you could upload that video in HD vs what looks like SD. More light would help too.
 
Great. Forum ate my reply.

Here's the best video/lighting I can get. Very little light in the room. I added a clip light to help, I hope. YT for some reason is not allowing me to choose HD for uploads. No idea why.

YouTube

What I have found that works to make it go every time is to push on that tensioning arm on the left. Whether it's the lever itself, the airpot, an adjustment, I don't know.
 
Looks to me like it's a solenoid/relay issue...some kind of stickiness going on.

Sweetbeats may have a better idea of what it is...he's gone in deeper with this type of stuff than I have. :D
 
Great. Forum ate my reply.

Here's the best video/lighting I can get. Very little light in the room. I added a clip light to help, I hope. YT for some reason is not allowing me to choose HD for uploads. No idea why.

YouTube

What I have found that works to make it go every time is to push on that tensioning arm on the left. Whether it's the lever itself, the airpot, an adjustment, I don't know.

And I don't know either, but your follow up video didn't address any of the elements I'm asking for in order to begin attempting to help you. Let's not get side-tracked with the airpot and tension arm hardware yet.

1. I need to see what happens to the tape path from supply reel to takeup reel when you engage PLAY.
2. I need to see this all at the same time. Get a buddy to hold your video capture device so you can press PLAY while the video is steady and capturing the full tape path.
3. Please have your buddy hold the video capture device in landscape orientation vs portrait...this will maximize the video capturing the stuff we need to see.
4. Figure out how to get more light on the transport when you do the above.

Keep in mind my experience with MCI tape machines is limited...like, I was physically in a room with a JH-110A once. That's it. So you'll need to decide if its too much trouble for you to do what I'm asking above in order to get assistance from somebody that knows nothing about your machine. But if I was there? the first thing I'd be doing is pressing PLAY and watching what happens across the entire tape path...I'm not there, so I'm relying on a video. I don't know how to begin helping without that. From there I'd be cracking open the manual, studying the transport setup and maintenance section as well as the theory of operation section to study electro-mechanically what actually happens when you press PLAY...how it works...hopefully there is a theory of operation section. I don't have a JH-24 manual.
 
So to clarify, you’re looking for an overview of the entire top of the deck when this happens, is that correct? As sad as it’s going to sound I don’t have a buddy. I’m out here all by myself in the middle of nowhere with this machine. I do have a kind of attachment that I’ve made for a mic stand which I may be able to clip the phone to and shoot from a distance while I try it. Hopefully that will show you what you’re looking for. And again I apologize about the lighting and the apparent inability to upload HD video from my phone.
 
Yes that's right...ideally the video capture device is stable and capturing the entire transport from one reel to the other reel. I want to see the behavior of the supply reel, capstan and pinch roller, and takeup reel...the tension arms, and of course the tape. If you have something of a stand/mount for your video capture device use it. show in the video what happens when you go from STOP to PLAY (including getting into PLAY mode with the manipulation of the supply tension arm), then SOPT and PLAY again, then maybe PLAY to FFWD to PLAY, to REW to PLAY, and maybe from the fast-wind modes to STOP. Basically a video taking the transport through all the different mode transitions if that makes sense, but in particular STOP to PLAY to STOP to PLAY.
 
Okay, first off: secret to uploading hi res videos from my phone is to upload from the gallery, not the camera app. So, I have that figured out.
Second, here, I hope, is a video that will show clearly enough what is happening. I've been working on this machine on and off about 40 hours over the last three days, so apologies for the rambling.

YouTube

I have, as I said, a really nice printed manual, and apparently, I can't scan it. These drawings are 11" tall, and some of them several pages long. I did find, as mentioned previously, a PDF version of the manual, here:

Free MCI Schematics and Manuals - from AnalogRules.com

It's available as a free download if you follow his anti spam measures. I don't know the guy who did the scanning, and I don't know how he'd feel about me uploading it somewhere else, but I can. The compressed version is 96MB, so it's not small. The autolocator is ch. 5, and the power supply is ch. 6. It has extensive power supply drawings starting about page 6-3.

I did notice as I was shooting the video that if I put tracks into record mode and hit record and play (while jiggling the tension arm), the blue and red lamps above the appropriate meters do light, even though the VU back lights are still out, and the blue lights do not light as they used to when the "Input" mode was selected on the ALIII.
The manual says to do multi-track recording sync'ed with previous tracks, the procedure is to press both the Input and Auto buttons on the ALIII.
 
I've got the manual from analogrules.com, but its a mess.

Will just take longer to find things because there are duplicate pages and things are out of order.

Anyway, thanks for the effort on the video. It is helpful...I wish there was more machine and less you...no offense. And just be aware many times you are making reference to indicators or switches on things we can't see in the video so there's no way to help with those references.

At 6:10 I *really* wish I could see what the supply side tension arm or "dancer arm" is doing when you are rotating the takeup reel counter clockwise but my view of the left half of the transport is blocked.

At 8:40, Sean, STOP plugging and unplugging things with the machine powered. ALWAYS assume hot plugging/unplugging is a strict no-no. That's how you created one of your current major issues.

Regarding the status lamps and VU lamps, I'll look at the schematic when I have time, but you don't have a simple fuse issue here. Because the status lamps light under some conditions they are supposed to light but not others, there is a switching logic issue, and that is going to be way beyond me to begin sorting out without being able to be at the machine and with my lack of familiarity with the machine. I hate to say it, but I believe something more complex that a fuse got fried when you were hot-swapping lamps. If indeed the lamps are powered by the 24V supply, my hunch is you shorted across the the + and common poles of the lamp socket causing a brief over-current condition effecting logic circuitry. I may be very wrong. I'll see if I can identify where the fuses are located. But, again, that's going to take time for me to read a manual to a machine I don't own, a manual version that is out of order with duplicate and maybe missing pages. I may have time to do this sometime in the next week or two.

As far as the PLAY issue I need to know what the dancer arm does when you are manually rotating the takeup reel counter-clockwise when the machine is in the fault state. Does that make sense?
 
I took another one, where hopefully I stay out of the way enough for you to see that. I'll post the link as soon as it's finished uploading.
 
AFA the video above...and just my gut observation...it's a sensor and/or relay issue.
The reason it's jumping into Play form RW...is that there is still some motion, the tape hasn't stopped and "clicked" into the Stop mode.
When you press play and nothing move...you also hear nothing. When you just lightly bump the reel, you hear that solenoid relay kick in, and the tape starts.

I personally wouldn't think it has anything to do with "tension"...and more to do with a senor/switch/relay not engaging.

On my own MX-80, when it goes into Play from an initial tape loading position...IOW, the tape cover/protector is down...sometimes that cover will not pop-up when Play is engaged (otherwise, my deck works fine)...and if I manually push down on the tape cover and hit the Play button, it will click, and release. That tape cover is also moved by a solenoid type mechanism (I think I'm describing it correctly).
So I think you have the same issue, just with a different switch, in a different place...and I think you already found which one it is in the earlier video when you were looking down underneath, and you push the mechanism and it clicked/release and the tape started moving.

I would trace from the Play button/switch to that mechanism, which to me looks also like a solenoid type relay/switch deal...and see if there are contacts, etc...or it just might be that there is a "dead spot" somewhere and it just sits there at times.

If the deck otherwise performs as it should, I mean, if all you have to do is nudge the reel when you engage Play at times, and otherwise everything else is working well...it's not really a show-stopper, but of course, something you would want to fix is possible.

My tape cover switch...I just keep nudging it. :D
Also...I notice with my deck, that the longer I don't power it up to use it...the more chance that when I do, that cover switch is not going to engage. Then after I have the deck going for a day or two while recording...at some point it "loosens up" and then the tape cover will engage normally every time I hit Play.
If your deck was sitting ins storage for a longer time...it might just be "stiff" and needs some cleaning and TLC and it will all come back to life.
 
Thanks, Miroslav. Sitting doesn't seem to help these machines at all, for sure. This particular one was in use for 30 years, then sat for four years when the previous owner moved to a digital system. Contacts go bad, solenoids get sticky, all kinds of things like that. And that's assuming of course, you don't get help from mice or bugs.
 
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