MCI JH110

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sonicmook56
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MCI JH110

Post by sonicmook56 » Tue Dec 26, 2006 12:30 pm

I should really buy a manual for this thing, but just a few questions first.

How can one tell what model MCI your dealing with? (a,b, or c?) Mine has a autolocator and is electronicly ballanced, but does not say a,b or c anywhere.

Torque limit button? I have no idea what this does.
"bias" button? I have no idea what this does either.

Thanks

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Post by stellavox » Wed Dec 27, 2006 4:58 am

On my decks there is/are one or two small nameplate(s) with the model info on the panel where the power transistors and power cable sockets are located. Also can lool on the large surface where the PC cards are located. The larger card on the left-hand side is the motor torque board. If there is a switch on the bottom with a red knob then the deck is a 110 or 110A, If no switch then it could be a C or D. Original autocorrelator had only two pushbuttons, return and reset - later B decks had a bunch of buttons. Torque limit switch does just that - limits rewind / fast forward torque if you are using reels smaller than 10".

O yeah, later - B/C decks had a 10 turn variable speed adjust pot - earlier machines had single turn pot.

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Post by sonicmook56 » Sun Dec 31, 2006 4:35 pm

That's good info.

I'm about ready to put this deck out on the corner but before I do, I want to adjust proper tension to see if that fixes it. Anyone have a tension procedure for this deck?

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Post by brianroth » Mon Jan 01, 2007 2:28 am

If the MCI has electronically balanced I/O, it will be a "B" or "C".

The "C" decks had TWO rollers that the tape threaded around on the supply side of the tape path (left of the head block). "B" had only a single roller.

Reel servo (and hence tensions) are pretty easy to set up. Part of this is from memory, so I may be slightly off.

1. Adjust the offset nulls. With tape loaded and machine in "stop" and reels not "creeping", measure the voltage at TP1 and TP2 located near the bottom edge of the Analog Torque Board (large card on the left), then tweak the Offset Null pots for as close to 0VDC as possible. It's a touchy adjustment. Each test point is semi-close to the Null pot which will affect it.

2. Adjust the Idle pots. Remove the tape, then put something into the tape sensor (the "electric eyeball" located to the right of the head block) to fool the machine into thinking tape is loaded. Adjust the Idle pots so that each spindle lazily spins at maybe 2-3 seconds per rotation. Reload a full 10" reel pack of tape and verify there is no "creep" with the full tape pack loaded on the supply spindle and then on the takeup spindle. Reduce the setting of the Idle pots a tad if you detect any creeping.

3. I forget the name of the third set of tweaker pots but they set the play tension. Find the ones NOT labelled Idle or Offset. FF a 10" roll of tape to approx. midpoint (equal amounts of tape on both reels). Go into Play, and adjust the left hand pot so that the "dancer arm" (located near the left hand roller) is approx. midway in position. Then while in Play mode, manually push the pinch roller away from the capstan and adjust the right hand pot so that the tape still runs at approx. the correct speed.

There are a ton of other nuances with MCI machines, like does yours have the red colored sockets for the chips on the transport control cards (red sockets = junk/must be replaced)? Have all of the Molex connector pins been resoldered?

Bri
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Post by sonicmook56 » Mon Jan 01, 2007 8:56 pm

Awsome. This is the info I was looking for.

I think I have a "C" machine.

Mine has all the crappy red sockets. Sometimes the transport goes crazy and I have to push on them a bit to bring it around.

Ill replace them if I can get this machine not to sound like complete shit.

resolder the molex pins because of cold solder joints? I'll look at them when I'm setting the tension.

What's the "bias" button on the audio I/O for?

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Post by brianroth » Thu Jan 04, 2007 1:23 am

There are two identical rollers on a "B" (on each side of the head block) that are maybe 1.5" in diameter. The "C" added a second identical roller on the supply side of the head block for a total of three identical rollers. This picture (easy Google find) sure looks like a C and **not** a B since there are 2 rollers to the left of the headblock:

http://analogrules.com/Gallery/MCI/e5_1

The "bad red" IC sockets were only used on a 110B AFAIK.

If the transport totally changes it's mood when you press on the boards under the transport, it can definitely be due to the crappy IC sockets OR the Molex "bed of nails" pins that are soldered onto the transport motherboard (and to a lesser extent the pins that are stuffed inside of the white nylon sockets that are on the rear of the various transport circuit boards).

The bias button is quasi-useless...it gives you a "return to" point on the VU meter when changing bias setup from one tape formulation to another.

Bri
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Post by CurtZHP » Thu Jan 04, 2007 10:20 am

RE: Bias button......

Yeah, what Brian said. It doesn't do anything unless you're calibrating the machine.

I have what appears to be a "C" model, that I just finished setting up.
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More on the 110

Post by stellavox » Fri Jan 05, 2007 6:04 am

I have 2 "B"s (or not to be - that is the question; HAD to put in some Shakespeare humor) which have the third large idler wheel on the left hand (supply) side, although one machine looks like it could have been added later.

It appears that MCI went to the heavy, black, head mounting plate with the "B" series. I have an "A" series headblock with a much thinner mounting plate and a light brown cover which snaps down over the whole headblock.

Another difference is that the "A" series appears to use very different record/playback electronics design. The boards look the same when you open the drawer, but careful examination shows them to contain significantly fewer parts. The playback board has a circular, white assembly soldered to it which I believe to be an encapsulated preamplifier - predating the low-noise IC's used in the "B" series. All the heads, although they look identical to the those on the later models, are of MUCH lower impedance and are NOT interchangeable.

I agree that all the IC sockets and interconnecting pins should be cleaned but not necessarily replaced. A few hours spent removing and cleaning all the boards/IC's with Cramolin red should take care of most problems. You will see significant tarnish on IC pins inserted into the dreaded "red sockets". Don't forget the boards/IC's in the R/P electronics.

I'm working on "upgrading" the electronics, as I've found the playback "sound" (at least) to be compromised. Will tackle the record portion next.

FInally, I'm looking for any spare 1/4" heads in decent shape that you may have. Also a flutter roller.

THANKS

Charles
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I am looking for B series heads and/or headblocks if any

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Post by brianroth » Fri Jan 05, 2007 10:54 pm

I had totally forgotten about this fact, but MCI *did* offer an upgrade/update kit for "B" machines after the "C" was introduced. Among other things, a second roller on the supply side was installed.

Sooooo.......the second left hand roller can be due to an after-the-fact upgrade on what was originally a "B" deck.

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Post by sonicmook56 » Sun Sep 23, 2007 10:39 pm

Bringing this post back from the dead...

I finaly got around to doing the transport alignment and now it's moving tape good.

Found a plaque that says this machine is indeed a "B" model with two rollers on the tape supply side... made in April of 81'.

A couple questions about mechanical alignments of the tape heads.

1. On the left side of each head, there is a small set screw to position the head.. Where should it be?

2. Wrap? I've never seen it on a machine before.. I bet it has somthing to do with #1..

3. Where to set the flutter ideler?


Sounds like complete shit. Can't record and reproduce a 1k tone well.

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Post by ladewd » Tue Sep 25, 2007 3:22 pm

The small setscrew to the left of the heads is the azimuth adjust. You'll need an alignment tape and o-scope to set it properly. The front and back set screws are for zenith. These also adjust head height. All three screws form a tripod like mounting for the head and they all interact with one another. You'll need flat plate and a good eye to align the height and zenith. Once you get those right, you can adjust the azimuth. Both channels should be in phase at 10kHz and higher.

Wrap is the angle which the head contacts the tape. This should be adjusted for max output at higher frequencies (10k or higher). Make sure the tensions are correct before adjusting the wrap.

The scrape flutter filter (flutter idler) is a bit painful to adjust. Record a signal at 12-13kHz and listen to the output on some headphones. Stop and start the scrape flutter filter with your finger and you'll hear a high freq noise almost a hissing sound when you stop it. The idea is to only let it barely contact the tape while still filtering out this hi freq sound. It really bothers your ears to do this, and there is a box called an Altair flutter meter that may make it a little less painful, but they're hard to find. If you put too much of this roller into the tape path, it'll screw up tape to head contact.

CA

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Post by ladewd » Tue Sep 25, 2007 8:38 pm

Now that I'm home from work I can get into a little more detail. On the rec and repro heads, you'll see a groove in the head above and below the tracks. These will assist you in eye-balling the correct head height. Adjust the front set screw so that the tape rides in the middle of these grooves. Check the erase head and make sure you can see a bit of the top and bottom part of the silver area in relation to the tape.

Next, you need to get a small flat block and rest it on the incoming guide of the headstack and erase head. Adjust the back screw so that the erase head is flat against the block (you're using the incoming fast guide as your perpendicularity reference). Then you can use the erase head as a reference for the rec head (and rec for repro). When you're doing these adjustments pull the scrape flutter filter (now referred to as the SFF) back so that it doesn't interfere with what you're doing. What you want to achieve is to have all heads straight with one another and the guides. You can eye-ball the azimuth (side to side head tilt) at this point to keep things closer. You'll need to go around a few times until everything looks straight. Its easier than it sounds.

Once you get the heads straight you'll need to adjust the azimuth with an alignment tape and you can either do an XY pattern on the scope, or look at both sine waves at low and high frequencies to make sure they're in phase throught the frequency sweep. I prefer the latter, but its a bit trickier.

You'll need to adjust azimuth on both rec and repro heads. Then put a blank reel of tape on the machine, put it in record, and monitor the repro head with a scope and make sure everything is still in phase (you'll probably need to adjust one of the heads, so make it the record head and use the repro head as the azimuth reference.

Since you've got your tensions aligned already, you can go to the head wrap adjustment. Put an alignment tape on (15ips is a good choice, but the adjusments get more critical as the tape speed slows down, so at the end check the all azimuth and wrap adjustments at low speed). Adjust the wrap screw so that you get max amplitude out of the head above 10kHz. At 7.5ips, the rec head doesn't have enough frequency response to effectively adjust the wrap (or azimuth) while playing back the alignment tape.

Next put a blank tape on record (monitor off the repro head) and adjust the wrap of both the record and repro heads for max signal at high freqs. If you drag the supply reel with your finger, you shouldn't see the amplitude go up, only down. This is an indication that the wrap is correctly adjusted.

Once you get this done, you can adjust the SFF in the manner I described above.

Have fun and if you need clarification of any of the steps, I'll be glad to help out. There may be some redundancy here, but that's the way I set up a JH110 headstack.

A manual is a must to have lying around.

CA

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Post by brianroth » Tue Sep 25, 2007 10:28 pm

Some random comments....

First of all, be sure the tape transport tensions are set correctly. Assuming that the "dancer arm" (which sits next to the roller to the left of the head block) is approximately centered in it's mechanical range, via the pot on the analog torque board labelled "left play tension" or some such, then by forcing the pinch roller away from the tape and capstan, the play speed should stay rasonably close to speed and not go racing, or drag to a stop. The "right play tension" poy sets that parameter, and it should be pretty much the same regardless of tape pack.

Unless some one has really messed up the head adjustments (or, replaced a head), the height and zenith should be OK, meaning that only azimuth and wrap need to be adjusted.

You can check zenith by "painting" the face of the head with a Sharpie marker pen, then running some "I don't care" tape in play mode for a minute or two. You can then see the "silver" showing where the tape has smoothed off the Sharpie marker, and it should be a rectangle centered top to bottom. Denatured alcohol will clean off the rest of the Sharpie ink after you're done.

For a "flat block", someone at MCI suggested (eons ago!) having some plate glass blocks cut, vs. using a metal machinist blocks, which are aluminum or steel. I still have a set of glass blocks (from 1/4"-thick plate) in various lenghts and widths, which were made up by the same shop which was doing the custom studio windows on a project a couple decades ago <g>.

It's a bigger issue getting everything lined up on, say, a 2" machine vs. a 1/4", but it's still important that everything in the tape path be perpendicular.

Bri
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Post by Jim Williams » Wed Sep 26, 2007 8:23 am

The C is the best machine they ever made. It can be aligned to record at +9 db and still have very low .15% THD. Stock they do +3 at .55% THD. It can also record flat out to 32k hz when properly aligned. Replacing the opamps is needed, the LME49710 singles and the LM4562 duals are great drop in's. Then you have that row of "ceramic" EQ caps for various tape speeds, replace those with Wima FKP-2's or MIT MultiCaps. Replace the dull and small sounding LM394 transistor pair off the heads with the AD MAT-02's. Replace the bipolar coupling caps with Panasonic FM, just orient the + pin towards the + offsets of the opamps. With the National parts, some coupling caps may be able to be bypassed as the opamps have very low dc offset. Do bypass any signal electrolytic caps with Wima MKP-2 .01 uf polyprop caps for details and air.

Then do a precise alignment with an Audio Precision analyzer to nail bias points, etc.
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Post by brianroth » Wed Sep 26, 2007 9:18 am

Thanks Jim! The audio path upgrade info is cool...

I vaguely recall a negative feedback path cap which limited the HF response in the I/O stages, regardless of opamp. Reducing that cap's value opened up the top end, IIRC.

It still takes some TLC to get the tape path dead-nuts-right, but it's a very decent machine....highly under-rated.


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