MCI JH-416 Story...

[pianodano]

The site above shows several of the Ampex machines with his improved electronics. Nice pitcures of the 416 console also.

 

[briank]

Yeah, Mr. Harned's ideas did go lots of places, but Its interesting to note that the first series of open reel machines they produced looked an awful lot like Ampex 440 fare. In fact the amp cards are interchangeable, as are the electronics power supplies. Hmmm.

Yep! From this article:

"I got into the tape recorder business in an interesting way. I had built a console for Sidney Nation of King Records in Cincinnati and he, Mack Emmerman, and Bob Richardson had a bunch of Ampex 350 tape recorder with transports that still ran well, but electronics that were on the verge of quitting completely. So in 1968 Sid, Bob and Mack got together and hired me to design and build some new "solid state" electronics for the old transports. My electronics proved to be quieter, had lower distortion, and they didn't have the 'Bias Rocks' common to so many earlier designs.

"I filled this order for 100 units and I thought that would be the end of it, but when the word got around the industry that there was this guy in Florida building these 'solid state' electronics, a lot more people became interested in them. All of a sudden I'm sitting there looking at orders for two of three hundred of these things. People bought my electronics to use with the older transports, and we continued to sell these for several years. And that's where it all started for MCI in the tape recorder business.

Cory, thanks for the PSU pics! Nice and simple (and made of tank parts as expected, hehe!) You going to rebuild it? (that was a dumb question, wasn't it?) It actually looks quite a lot like our JH-110's PSU.

 

[sweetbeats]

I'm sure I will rebuild it, initially I may just do the main filter caps. The seller was nice enough to test it and replaced a transistor, the lamps and the cooling fan. Now all rails work.

I was mistaken about the interconnect cable coming with it...it is not BUT he's including the cinch connector so I can make my own and I've already got the perfect bulk cable for the job.

So power supply tested and operational with some new bits, cinch connector and a schematic for $125 + S&H which I consider to be a pretty reasonable deal. By the pictures I would say it is in better than average condition.

 

[briank]

Absolutely, that's a good deal especially with the fresh transistor, lamps, fan and a cinch connector ready to be wired up. What's the transistor, 2N3055H?

 

[sweetbeats]

Yep! 2N3055, assuming it was the pass transistor that was bad (he said the +24V rail was down when he first tested and found a bad transistor and I'm assuming it was the series pass for the +24V rail that was bad).

 

[briank]

Yep! 2N3055, assuming it was the pass transistor that was bad (he said the +24V rail was down when he first tested and found a bad transistor and I'm assuming it was the series pass for the +24V rail that was bad).

Ahh yes, MCIs are chock full of 'em. One thing most MCI guys seem to agree on is that if it's a 2N3055H that comes out, another "H" is what should go back in, I guess they were more rugged. Might want to check and see if these PSUs were originally fitted with the H version...if the replacement isn't but should be and it fries after too long, I'd look at putting in the more rugged version.

Although 2N3055s are cheap and very common, I've read that the H version are out of production and a pain to source, BUT it looks like ON Semiconductor is making an H version...not sure if the specs are the same but I want to look into that, would be great if there was indeed an inexpensive source of them!

 

[RICK FITZPATRICK]

Cory, you're completely insane.

I couldn't help myself

Well then, that explains it.

All I know is you're a complete glutton for analog punishment.

 

[sweetbeats]

I got some clarification...it wasn't the series pass transistor...it was an overload sensing IC which is a 741 in stock trim. The seller replaced it with a 5534 and that cooked under load so he is ordering a proper part.

 

[sweetbeats]

Getting to know you...

Can't help but tear open some of the stuff and have a look inside...been doing a lot of dialoging with some folks on the MCI forum and offline as I come to grips with wiring such a piece of equipment and how signal flows.

Its pretty neat how the global mode switches work in terms of changing the function of the inputs and outputs and the flexibility with the per channel mode control defeat switches.

I had to pull one of the faders and open it up.

Here it is with the mounting plate and dress panel. The mounting plate is a pretty impressive piece just from a machining standpoint as there is a milled section that gets very thin where the fader lever staggers to block dirt infiltration...tiny brass screws affix the dress panel to the mounting plate.

Here is the pack sitting next to an ALPS fader from my Soundtracs MX mixer...these ALPS faders are pretty common in Tascam M-300 and M-500 mixers and many others. The P&G fader has a longer throw and is just a chunk compared to the ALPS fader which is pretty chunky compared to standard faders:

And here it is opened up...you can see two microswitches at the bottom of the fader throw. One is actuated when the fader reaches the bottom of the throw, and the other is actuated if you further pull back on the fader when it is at the bottom of its throw...there is a spring in the wiper carriage to allow this and then to spring the carriage back to neutral once pressure is relaeased. I don't believe either of these switches are used in this application, but I believe they can accomplish a number of things like machine start and stop and that sort of thing.

 

[Muckelroy]

Wait, so this *does* or *does not* have moving fader automation? If so, how is it controlled? Did I miss something?

 

[sweetbeats]

No, no it doesn't...I believe P&G faders were the pack of choice for the early automation systems though...I'm pretty sure the JH-500 series mixers were the first MCI consoles to offer automation...that was the JH-50 system but it, uh...wasn't very..."good". But the switching in the faders could apply to all sorts of things as I mentioned machine control functions like stop and start. My Tascam BR-20T has provision for fader start and stop and those signals would come from switching such as is found in these fader packs.

One thing I really like about this mixer is that it is really rudimentary...no fancy bells and whistles like automation. I'm completely happy with the automation found in my own digits and motor control faculties...and I've got a DAW if I get an itch for automation functions since, of course, it is dripping with them.

 

[sweetbeats]

Yeah-yeah-yeah this is supposed to be a back-burner project but I am just smitten with this mixer.

Just a couple updates...I've been working through the very serious matter that the mixer is missing the wiring harness and most of the patchbay.

Part of what makes it a big issue to me is just getting my head around how the wiring works...the whole idea of there being no jacks on the mixer...the whole permanent wiring thing, and then how the patchfield works into things. You guys who have used consoles that are setup this way or worked with extensive patchfields before have this down I'm sure but for somebody like me who has exclusively used consoles with a jack field and where patchbays are sort of a helpful convenience component this is new; having the patchfield as an integral component to signal routing.

So mentally my brain is getting acclimated to how the wiring works which has helped me to solve one of the questionable bits which has to do with the terminal blocks in the back. My console has three blocks with something like 80 terminal sets (3 in and 3 out). The whole idea is that audio wiring from the mixer guts (the motherboard and the patch field) terminates on those blocks and then you terminate your studio wiring onto the corresponding sets of terminals and in this way you can make changes to your studio wiring as far as how it connects to the console without disturbing the internal wiring of the console.

Here's the issue:

The terminal blocks used on the early JH-400 consoles like mine were never really designed to be used with stranded wire...they were designed to be used with solid core telco wire. So there is a concern over connectivity and reliability. They are punch-type blocks so you don't have to solder wires up to it but often people do because of connection issues. My blocks have had such treatment and once you solder to it those terminals never work as punch terminals again.

Well I found these:

ICON Audio Rack-Mount Systems

Actually found 3 of them for $50 shipped.

That will take care of the 240 interconnects on the console with room to spare, they are designed for balanced audio and 22AWG stranded wire, etc. etc.

I had found a fella with a JH-416 that he was thinking of parting out and I was working on getting the complete harness, patchbays and terminal blocks, but I think I can work a higher quality/reliability solution for lower cost so I think I'm going that direction.

Anyway...here's something I didn't think about...since all the knobs are actually affixed with two set-screws each it takes relatively FOREVER to strip the knobs off as opposed to just pulling them off. The Rogan knobs commonly crack on these so I'm stripping them off to get an invenory of what's toasted, what's repairable and what's reusable...after a good cleaning...YOW but somebody shoulda washed their hands before using this thing for the past 3 decades...this is the filthiest mixer I've ever had to clean up.

These pictures just don't do it justice...one fader knob is cleaned up (the one in the foreground) and the gray round knob in the foreground is cleaned up...they take some work to get them clean. Also check out the genuine yellow-zinc plated set screws...

Another fun thing:

This mixer is +4dBu all the way through, whereas a lot of mixers that have +4 ins and outs are -10dBv internally, this mixer's native operating level is +4.

 

[pianodano]

Spray them down with 409. Let them set a minute or 2. Then put them in a pan of warm water with 409 in it and grab a toothbrush. It won't take too long to do them all.

 

[sweetbeats]

I'll have to try that, Danny...thanks!

I usually do soak them for a bit in warm water but with just hand soap...I'll have to try 409.

Finally got all the knobs removed. It took a long time. I sorted them into three categories: good to go, repairable, and toast. Looks like I have enough of the first two categories to cover at least 17 input modules which is good enough for now since my plan is to short-load the frame to 16.

I got the ADC punch panels. Very cool. They'll work out well:

I also discovered that it is very possible to bust the push switches on this thing when attempting to get the switch caps off.

As a result I have figured out how to actually disassemble the switches which will allow for a safe separation of the switch cap and the actuator, and at the same time allows for excellent access for cleaning all the metal contacts. I'm going to go that route with all the switches rather than shootin' DeoxIT in there and hopin' fer th' best. I'll be able to actually clean each contact surface.

Power supply is on the way.

 

[briank]

Holy macaroni, those are cool lookin'! Glad to see the progress on that console!

 

[sweetbeats]

Holy macaroni, those are cool lookin'! Glad to see the progress on that console!

Yeah, they are heavy-duty...and purpose-built for audio. They require a special punch-down tool but the manual version is, like, $30 or something so its not too bad, and considering I got the three panels for $50 I think I'm sitting pretty good with the cabling interface. It'll be a mini project to devise a system of mounting them on the back of the console in a way that looks like it "belongs", but I'll get there. At least I'm avoiding Tuchel/ELCO/EDAC/DSUB etc. nightmares...

 

[briank]

And how! Soldering Tuchels took me AGES and I still have some non-essential ones to do when time permits...your system looks more pleasant/less tedious for sure! Your re-cap will be much less of a PITA too! I envy the simplicity of that 400 on several levels!

 

[sweetbeats]

And how! Soldering Tuchels took me AGES and I still have some non-essential ones to do when time permits...your system looks more pleasant/less tedious for sure! Your re-cap will be much less of a PITA too! I envy the simplicity of that 400 on several levels!

Well, I'll have the pleasure of soldering up the entire patchbay and motherboard... But, yes, recapping will be relatively painless as will troubleshooting. Who knows how it'll be sonically, and certainly I'll be without some typical control surface conveniences...notice there are no lo-cut filters, phase switches, phantom enable switches...its pretty bare bones...but so is my old Chevy truck and I'll work on that any day as opposed to a contemporary vehicle.

It occurred to me that I never put up a copy of the listing pic...this is what I saw with the simple caption "vintage mixer"...now, wouldn't YOU ask "hey what kind of mier is that anyway?"

 

[briank]

Well, I'll have the pleasure of soldering up the entire patchbay and motherboard... But, yes, recapping will be relatively painless as will troubleshooting. Who knows how it'll be sonically,

Touche!

I'll be interested to see how it sounds (and what actually does sound ) when you get it to the point that you can power it up and run some signal through it.

I can tell you that in addition to increased functionality, there's definitely been a sonic change for the better as I've been re-capping my modules, and lots of things coming back to life...EQ sections that were partially or totally dead before are not only working well but are fairly transparent when switched into the circuit vs. bypassed, lamps are back to life, and as you lose bass as caps go out of spec, I've had quite measurable increases in the low end on many channels. Doing before and after oscillator sweeps, I'm getting back an average of 2.5dB-3.5dB back up to flat between 20hz-250hz in some cases. There are a bunch of different values and cap brands in my modules, and I've found failures in every type, brand and size. After 30+ years in a warm running console, some of 'em just crap out.

I expect that sonically when it's all done, your 400 will probably have more girth in character compared to my 600 with the more generous power rails and the simpler circuits. Sure you don't have the conveniences of high and low pass filters, 48v, phase flips, VCAs etc, but sonically this all translates to pura freakin' vida! I expect this console will in some way have more in common with our 16ch Yamaha PM1000 than my MCI 600, especially in terms of headroom, EQ, and general design simplicity. Your 400 will have some mojo workin' without question!

 

[sweetbeats]

Just some shots of the power supply...

Overview:

Yep...the right rack ear is bent back. Wasn't packed well IMO. Its repairable though I wish I didn't have that to do when it TOTALLY could have been avoided.

Closeup of the damage:

So enough about that...on to the finer points of the supply...

This is a fan-cooled bipolar 24VDC regulated supply that powers the relay logic, lamps and audio on separate legs. It is short circuit and overload protected. The chassis is a really neat design as the regulator card is accessible through a hatch in the front panel that locks with 1/4-turn spring-loaded thumb-screws, and by removing six screws the top plate comes off and the main filter caps are screw terminal and clamp mounted so easy to replace if needed, and my FAVORITE little feature is the series pass transistor heatsink assembly...remove 4 screws and unplug the multipin connector and the whole thing...housing, heatsinks and fan slides out for clear access for cleaning. Very smart design. The main transformer is a hefty chunk. The mixer and power supply interface over a 12-pin Jones Cinch connector. I have to get some cabling, but a used connector came with the supply.

Here's the little hatch removed to access the regulator card which you see in there:

And here's the card itself:

And here's a look inside...from the left the transistor heatsink assembly (you can see the white multipin connector on top there), the regulator card socket and then right next to that the main filter caps (the two silver cans) and then the main transformer:

Unplug the multipin connector to the transistor heatsink assembly...

Remove the pairs of screws to either side of the cooling fan...

And the whole thing slides right out!

Really nice heatsinks...

And a shot of the mixer interface connector and plug:

And last but not least a shot of the one blue eye that says "let's go...punk":