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MCI JH-24 maintenance

Discussion in 'Vintage Analog Gear' started by fabmusic, Sep 3, 2010.

  1. fabmusic

    fabmusic Active Member

    I work at my fathers studio. He owns a MCI JH-24, for a while it was not used much due to the inconvenience, but it sounds really good, and we are wanting to use it more. He has asked me to look into what kind of maintenance work needs to be done on it. So I am asking if anyone can refer me to any sort of text or the equivalent so i can figure out how to keep this thing in good shape.:cool:
     
  2. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Where are you located...country, city, etc.?
     
  3. RemyRAD

    RemyRAD Well-Known Member

    A JH 24 can be a finicky beast. This isn't like keeping your car going. So he has the machine does he have the manual? You really need a manual for this TTL based transport. These MCI machines frequently had electronically controlled tape tensions that would frequently drift. And the tape tension adjustments can be extremely infuriating if you don't get them absolutely right. The audio electronics are a little more straightforward & stable in comparison to the transport. Power supply issues are a big factor with the transport. Thankfully, this machine works great with any kind of tape you throw at it. But you're going to need a playback alignment tape such as the MRL Magnetic Reference Laboratory alignment tapes. I recommend you get the inexpensive one with the limited frequency selection. Otherwise if you want the full blown test tape you'll drop a chunk of cash. And don't forget you need a heck of a good head demagnetizer. Then you have to learn how to properly bias the tape. This is both a science and an art that is difficult for folks just getting into it to understand. It not only affects frequency response but how deep the magnetic field is focused into the tape. I could go on but I won't. There aren't any real good books on tape recorder upkeep, maintenance, alignments. And even when you have the manual they are generally rather confusing in their descriptive nature on how to align things. Most folks believe that you need a 3rd harmonic distortion analyzer to properly perform the bias adjustment. But that is not necessarily the Gospel. One can still tweak up a machine if the machines metering is still relatively operational. While we all would like to have a perfectly flat response from 20-20,000 Hz realistically, you're looking at 50-15,000, + or - 2 DB for government work. That's perfectly adequate and perfectly realistic. Most folks are full of hooey that believe they need response beyond those limits. Sure, some folks can hear the difference. But it doesn't make any difference. It's the integrity of your recording capabilities that makes all the difference.

    I think you get the idea?
    Mx. Remy Ann David
     
  4. fabmusic

    fabmusic Active Member

    moonbaby- there are people in my area who can service it, i'm just trying to figure out how i can save a buck

    remyRAD- thank you for your advice. I understand very little of what you are talking about. I am not sure if we own the manual, if not are they hard to find? I know it will take a lot of research, trial and error, and snooping around the internet to figure this stuff out, but i'm willing, and hopefully able.
     
  5. RemyRAD

    RemyRAD Well-Known Member

    All of those MCI machines were popular across our country. And because of their original cloned electronics, it offered complete compatibility with similar Ampex products. Many people feel that the Ampex MM 1000/1100/1200 were the finest tracking recorders of all time. And if you feel that way then the MCI's will also sound like those. I personally liked their transformer based input & output as opposed to all of that transformer less craze we went through in the late 1970s.

    I love old MCI's
    Mx. Remy Ann David
     
  6. Davedog

    Davedog Distinguished Member

    If you are in the DC area then Remy might take a look at it. Remy??
     
  7. RemyRAD

    RemyRAD Well-Known Member

    I tweaked one of those machines last year for someone. Those transport logic boards are big problems in those machines. Plus a lot of those joystick shuttle controllers can no longer be repaired. Not a mechanical problem but are now an unavailable chip. And MCI made one critical mistake in the production of most of their machines. Their transport logic boards are affixed to a transport motherboard via MOLEX connector/pins that are not goldplated. This was stupid personified. Half of the repairs to these machines when they have transport problems is simply crunching the logic or other controller boards off & back on again. Then tweaking all of your tensions, startup torque, etc.. Had they used goldplated pins, these machines would have been a lot more reliable. The analogy would be the goldplated edge connectors & circuit board connections on the Ampex MM 1100/1200 series. Which you'll also find on 3M machines & Studers. So connectivity problems are a frequent issue. Hey, at least they were cheaper. A lot of people think that the Ampex MM 1100/1200 series machines were the finest sounding machines because of their discrete transistor circuitry. If you had an early MCI machine, you have the same audio electronics. However their later machines were all IC chip 5534 series based electronics and while they were clean sounding, they didn't have the balls of the earlier discrete transistor models.

    I don't own any just Scully & Ampex and a few others
    Mx. Remy Ann David
     
  8. fabmusic

    fabmusic Active Member

    so i found out that we have the alignment tape and the manual. I'm currently going over the manual so i can understand this hunk of machinery. One thing i read is that i have to replace all of the red IC connectors, any comments?
     
  9. RemyRAD

    RemyRAD Well-Known Member

    LOL, don't eat the brown acid either. Depending upon the age, the alignment tape may or may not be usable? And you don't want to use the alignment tape without de-magnetizing the entire head stack assembly. Not doing that can result in the erasure of those most important high frequencies on the tape that you need for proper calibration. And de-magnetizing a 2 inch stack cannot be done with a little toy head de-magnetizer from RadioShack. And then there's the art in the process of doing it. Never quickly and never perpendicular to the face of the head. And even though your Test Tape has low frequencies on it, YOU DON'T TOUCH THE PLAYBACK LOW-FREQUENCY EQUALIZER CONTROLS WITH THE PLAYBACK ALIGNMENT TAPE. Those get adjusted while you're recording, in playback monitor. You only use the test tape at those frequencies in playback for a rough observation and they will always be higher at the low frequencies than they should be. This is due to " Fringing effect". That is unless an announcement is made at the beginning of the tape or there is some notification on the box that the tape has been adjusted for multi-track playback. Otherwise, this tape is a single 2 inch wide track made from special custom heads. So many people make that mistake that it's not even funny. Even NBC radio in Washington DC had made that mistake when I came on board in 1981. And to think, RCA actually made their own tape recorders and RCA owned NBC. We had plenty of RCA reel to reel recorders back then. Thankfully, they purchased some good cart machines. Have you ever considered matrixing your left & right record channels into MS/Middle Side and then decoding back to left & right on playback? No more foggy sounding azimuth errors that way. Just a little shift in the left right imaging which is a lot easier to deal with especially on a mono radio. So while people like to utilize MS miking and recording applications, it has many other applications when processing audio. I think I'm rambling??

    Actually, I should walk everybody through a simple alignment procedure. A lot of test equipment really isn't necessary. In fact, your DAW can be utilized quite nicely in this application. Unfortunately, doing a third harmonic distortion analyzation would most certainly require a workstation with 192 kHz sampling frequency and preferably 24-bit. But then most folks really don't care about the third harmonic anymore anyhow. Most folks just measure THD instead of just the third. And while most recorders VU meters are not super accurate, they are accurate enough to get you within 1 DB generally. Which is all we ever did at Media Sound in NYC. Of course you go the extra mile if the machine needs any kind of real service. And if you are doing most of your work in-house, record a line that only needs to be done when you change batches of tape or interchange between other studios. Of course periodic alignment is necessary since tape is essentially a long-running 1.5 mil thick metal file. And while " glass heads", ferrite & ceramics could make the heads last a long time, the softer the metal the more ferrous. So actually they had to did last the longest were the best sounding and then you could also have them professionally refinished which would give you added life while also improving the way the head functioned because the thinner the gap the better. Not wider except for the record head. This is why most early multitrack machines sounded horrible when you played back through the record head. Lousy high frequency response and lower output level. The later 1970s brought us machines whose record head playback function was more like the playback head. I'm still rambling. I'm a plethora of useless information in the 21st century.

    Did I say I still have my custom silverplated 1881 Cornet? No, I didn't get it new!
    Mx. Remy Ann David
     
  10. Chris Uehlein

    Chris Uehlein Active Member

    Boy, I got an MCI JH24 fully refurbished by Chris Mara in Nashville and he is a ringer! What a genius, he got this thing sounding absolutely perfect. There is a machine he refurbished up on eBay right now and I've been watching it and drooling, hoping someone cool will be able to bid on it! Not a single bid yet!
     
  11. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    I was about to talk about Chris Mara too
    I found this video on vintage king :
    View: https://www.youtube.com/watch?v=UVWEMhP6-qs#t=18

    Seems that they restore them entirely including boards etc... They might have the ressources to get you going.
     

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