New to me MCI JH24 - stupid annoying problem

I just saw this today. I worked at MCI and worked on a shitload of JH-24’s. It’s been 30 years since I’ve even thought about these machines. What’s stuck in my memory, is the machine doesn’t know it’s actually in stop so it won’t go into play until you move the supply reel back a bit to add tension.

Look at the Analog Torque Board alignment. This sets tensions and offsets. All you need is a voltmeter, a manual, a tweaker and follow the alignment procedure in the manual. You may as well get your hands dirty because these machines need constant maintenance and there is a huge shortage of people that work on them and we’re all dying off. Once you align the ATB, Then I’d troubleshoot the other problem. The only thing that sticks in my mind is this problem is related to a “motion sensing” issue. I seem to think it’s related to the tachs which are mounted to the rear of the reel motors. They’re not fun to find or replace. Sony pretty much demolished MCI and their support system.

BTW, I currently work for David Kulka at Studio Electronics, but I gave up on tape machines a few years back. You tend to get married to them, if you get my drift, and since you’re always the last to have worked on it, you’re always responsible to keep them running however old they may be.

I would start getting acquainted with the machine and it’s idiosyncrasies. That’s the best advice I can offer you. Getting a hold of Steve Sadler in Nashville may be a good option for you. He charges for telephone support, but he’s been working on these machines longer than I have and if you can figure out how to use a meter and scope, he can walk you through any repair. We did this at MCI for years since the damn things weren’t exactly portable. You can PM me if you have any questions.
 
With reference to running gear '24/7'. I would not because electrolytic capacitors have a finite life and we are talking OLD capacitors to start with!
Most gear was built with '85'C rated capacitors which means they have a life span of just 1000 hours at 85C. Of course that is statistical and in any case the capacitors are not likely to be AT 85C the failure rated decreases as temperature but it is cumulative. Keeping gear on unnecessarily increases the chance of failure.
Any caps' that do need changing can usefully be swapped for 105C types and modern components will likely be no larger than the oldies.

I think the concept of never turning stuff off stated with valves, filament stress. Valves have long since become far more rugged (well some of them!) and a filament failure is a very rare event.

Keeping gear at an equitable temperature but powered down makes sense. You can buy 'Piano Heaters'. Aluminium tubes rated at about 50W per foot and about 3/4" diameter. As the name suggest, these are designed to go into pianos and keep them happy in the cold,cold church. "Tool clip' one under the machine and it will keep it nicely above ambient and quite cheaply.

Dave.
 
I would agree with shutting things down when not in use. I used to live in Florida which had constant lightning and thunderstorms. I would literally unplug things when the weather got bad. As others in this thread have said, if your not going to use the machine shut it down. Warm it up an hour or so before using it. Learn how to do an audio alignment. Back in the ‘70’s and ‘80’s we would align the record Electronics every time we put a reel of tape on the machine. If you’re just playing back, it’s not necessary, but you should know how to align to tones that should have been previously recorded on the tape. Also, you should learn how to adjust azimuth from the tones on the tape.

You’re now the proud owner of a great piece of recording equipment. Don’t rush things and get to know the machine. MCI provided a full set of schematics and alignment procedures with all their equipment. Manufacturers simply don’t do this anymore. If you have any questions, I’d be glad to get the manual out of the garage and help, if I can. Somewhere down the line either hire a tech or learn yourself. It will be an adventure and you’ll learn a lot in the process, although being a tape recorder tech is about as valuable as a toaster repairman these days. I still say Steve Sadler could be your best bet until you feel more comfortable with the machine. He’s a bit on the gruff side, but once you get past that, he’s a great guy. If you need his contact info, let me know.

BTW, your lamp problem is not the result of a blown fuse. It’s possible that it’s a Lamp Driver board, but is more likely a blown device in the remote itself.

Cary
 
Thanks, Cary. I'll power down. I do keep stuff here plugged into a UPS with surge protector, which has save me in brown outs and off/on/off power flashes more than once, but I know lightning will just right over those.

You were the second person to say adjust the DC null and tensions, so I've been working through that this afternoon. Still have to nudge the left reel a little to get it started, but the play and idle tensions were off according to the book, and it ffwd/rwd now tilted back, and it didn't do that before, plus it no longer creeps at idle, so I must be making progress.

Sean
 
My biggest challenge so far was figuring out that when the book says "puck off", they mean "pinch roller defeat". I'm like, "puck off?" "Puck off what??"
 
That was a joke. Instead of fuck off, they used the term puck off. Yes this is the pinch roller defeat switch. Glad you’re reading the manual. We used to call pinch rollers pucks at the factory. So, puck off removes the pinch roller from the capstan.
 
And, to close the loop, I did the tension alignment, and it's playing now when I push the play button. I had to go through the procedures for both idle and play tension like, three times before I wasn't having a problem where I'd adjust one, and have another creep away. I guess it was that much out of adjustment.
But, I did what the manual said, persevered, and it worked!

Thanks again, all!
 
That’s awesome. Good job! Bet that’s satisfying. Yes, you often have to chase a few things around in a circle all the while honing in on everything being set right. I’m just excited it’s working right. :guitar:
 
Good to hear it was just the tension being out of whack, and not a problem with the sensors or anything.
 
The JH-24 was a very analog machine. Yes, there are many logic chips controlling things, but the tension calculations and obviously the audio is all analog. The only microprocessor in the machine is in the Auto-Locator. You’ll find with many of the analog adjustments you have to go around in circles a few times before everything comes into spec. The adjustments, especially on the Analog Torque Board are very interactive. One adjustment affects the other 3 so going through the adjustment several times is always neccesary. Just have confidence that what’s in the manual is tried and true. If something looks off by a mile, then something is broken. I never paid much attention to the troubleshooting hints in the manual. Although sometimes they can possibly point you in the right direction, more often than not, their solutions are not very effective.

Also keep the logic annunciator board around. We never used them at the factory, but they can come in handy if you ever need to troubleshoot any logic problems. It’s funny you found the board inside the machine, it was an option when purchasing the machine new. You’d think people would take care of them! Did the machine come with Extender cards for the audio boards? There should be a set of 3 if I remember correctly. You won’t need these for audio alignments, but if you ever need to troubleshoot an individual audio card, they are a necessity.

What year was the machine manufactured? We made them from around 1982 to 1987. The ones built after 1984 had Sony logos on them as well as MCI.

Cary
 
The JH-24 was a very analog machine. Yes, there are many logic chips controlling things, but the tension calculations and obviously the audio is all analog. The only microprocessor in the machine is in the Auto-Locator. You’ll find with many of the analog adjustments you have to go around in circles a few times before everything comes into spec. The adjustments, especially on the Analog Torque Board are very interactive. One adjustment affects the other 3 so going through the adjustment several times is always neccesary. Just have confidence that what’s in the manual is tried and true. If something looks off by a mile, then something is broken. I never paid much attention to the troubleshooting hints in the manual. Although sometimes they can possibly point you in the right direction, more often than not, their solutions are not very effective.

Also keep the logic annunciator board around. We never used them at the factory, but they can come in handy if you ever need to troubleshoot any logic problems. It’s funny you found the board inside the machine, it was an option when purchasing the machine new. You’d think people would take care of them! Did the machine come with Extender cards for the audio boards? There should be a set of 3 if I remember correctly. You won’t need these for audio alignments, but if you ever need to troubleshoot an individual audio card, they are a necessity.

What year was the machine manufactured? We made them from around 1982 to 1987. The ones built after 1984 had Sony logos on them as well as MCI.

Cary

This says it was made in July, 1982.

Extender cards? What do those do? I definitely don't have any, but I'll hunt for some if it's something I need.

Sean
 
Extender cards? What do those do?

This is what an extender card looks like, though this is for an Otari deck...but the ones for the MCI should look similar.

OTARI MTR10 / MTR12 AUDIO EXTENDER CARD | eBay

What they do is allow you to pull an audio card out...stick the extender in that channel slot...and then stick the audio card onto the extender.
That allows you full access to a given audio/channel card to work on it, adjust it, while it is plugged in and the deck powered up.

Without the extender card...you only really have access to the front edge of your audio/channel cards and whatever adjustment pots are there...which is OK for basic calibration stuff...but when you have to troubleshoot a card/channel...the extender card makes it a lot easier.

I have two for my Otari MX-80...I almost bought a 3rd as a back up. :D
That way I can have to audio/channel cards sticking out if needed rather than pull one out, test, put it back, move the extender card...etc...etc.

Also have an extender card for my Trident console, so I can raise up/out on channel strip and still have it connected to the console...and it has been a big help on a few occasions when I was overhauling the console and needed to troubleshoot a couple of odd issues.
 
One is all you really need....I just happened to run across a couple more, so I grabbed a second one as these are parts that are no longer manufactured.
 
On the JH-24 there are 3 different Extender cards. One for the reproduce board, one for the Rec/Cue card and one for the Bias card. They shouldn’t be too hard to find, there are a lot of these machines out there. You could contact David at Studio Electronics and see if he has a set. Every once and a while there’s a JH-24 sitting in the shop when I come in. We usually sell the parts and scrap them. It’s kind of painful for me seeing things I built getting junked. I don’t participate in that area of the business. I like to repair things.
 
On the JH-24 there are 3 different Extender cards. One for the reproduce board, one for the Rec/Cue card and one for the Bias card. They shouldn’t be too hard to find, there are a lot of these machines out there. You could contact David at Studio Electronics and see if he has a set. Every once and a while there’s a JH-24 sitting in the shop when I come in. We usually sell the parts and scrap them. It’s kind of painful for me seeing things I built getting junked. I don’t participate in that area of the business. I like to repair things.

Cool, thanks Cary. I only found one set, but the person who has them (though he does have all three) doesn't seem to know enough about them that I'd risk $60 each for a set.

Actually, I've bought a bunch of (so far little) stuff from Studio Electronics already. They were like the first result when I searched for replacement lamps for the VU meters. They seem very nice, and they ship really quickly, considering they're on the other side of the country from me. I haven't seen the cards on their site, but I'll keep looking. Weird that the optional Logic Annunciator was there, but not the standard extenders.
Hmm. Maybe, given where the annunciator was, I should hunt around in there with a flashlight.
 
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