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Otari MX-5050 Restoration Thread

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Otari MX-5050 Restoration Thread

Postby twelvepoint on Thu Oct 16, 2014 7:00 pm

Note: yo may have seen this on the Gear for Sale thread. I decided I'm going to take a stab at getting this thing running again, then maybe sell it. Or maybe not, although my wife would like to see it out of here.

Here's the back story:

Image
Image

I pulled this out of storage this weekend, and, well, it's a mess. First thing is it's filthy, so I need to get out some paper towels and compressed air. The pinch roller turned to goo, so that needs to be rebuilt. When I plugged it in the capstan spun, but the reel motors aren't turning and the solenoids that apply braking to the reels aren't releasing. I notice that with the electronic modules, the VU meters light up, but neither the red LEDs for recording "arm" nor the green LEDs for "sel/rep" are lighting up. This makes me think there's an issue with the power supply, and I just got a manual in the mail to help with the diagnosis.

The heads look decent, at least, and the last time I powered this up, about 7-8 years ago, all the motors worked, albeit a bit sluggishly.
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Re: Otari MX-5050 Restoration Thread

Postby twelvepoint on Thu Oct 16, 2014 7:11 pm

Current status: it's a lot cleaner now. And with the help of the manual I tracked down where several different AC voltages were coming in from the power transformer. In doing so I noticed a problem where 26VAC was coming in, and it turned out there's a problem with a trace on the motherboard, which you can see in the photo here (right above the screwdriver tip). I also noticed there's a 29VAC tap coming in elsewhere, which is fine on the AC side, but isn't producing a voltage on the rectified end.

Image


So, a couple questions:
1) How would you repair this trace? Piece of wire? Blob of solder?
2) Would you be concerned about this trace failure being from a short somewhere? I'm wondering if there might be an issue downstream that could have caused it and if I repair the trace, it might just fry again. Judging from the fact that there's another DC supply that's messed up, too, maybe I should just shotgun the whole supply.
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Re: Otari MX-5050 Restoration Thread

Postby twelvepoint on Thu Oct 16, 2014 10:04 pm

I ended up fixing that trace (used a very small piece of wire to span between the card slot and the PCB hole for the wire) and the transport works fine now. The modules are mostly powering up, except one VU light is out, and none of the green LEDs on the sep/rep buttons (the two black buttons on the lower left) turn on. I'm wondering if this is a power issue, or if I'm just dumb and there's some logical reason for them now working.

So I'll be looking at the power harness and see if all the supply voltages are right. I'm also fixing an issue with the input jacks on one module. Then I need to get that roller recovered.

At that point I should be able to clean the tape path, thread some tape, and do an alignment.

It's also cleaned up pretty nicely. I'll post some more photos next time I'm working on it.
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Re: Otari MX-5050 Restoration Thread

Postby greg on Fri Oct 17, 2014 12:34 pm

Cool!
Keep it coming. I love swamp monsters being brought back to life, cleaned up and taken to the ball.

Athan or Terry's Rubber Rollers can supply a replacement pinch roller.

Usually I bridge a gap in the trace like that with a cut component lead or solid core wire. If it's a wide ground plane, I'll use a flattened, tinned length of solder braid.
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Re: Otari MX-5050 Restoration Thread

Postby twelvepoint on Fri Oct 17, 2014 1:00 pm

The latest problem seems to be that there's a bias circuit that should be powered by +29VDC and that doesn't seem to be getting power. The bias circuit is on the same board as the one I was just looking at and it looks like 29VDC goes off the board, gets switched by a transistor, and comes back to the bias section on the same board.

Without looking at the schematic or researching the type of transistor, I'm seeing 29V going to one leg of the transistor, zero volts coming out, and around 1.6V going to what appears to be the base. I'm assuming this is a transistor that just switches on or off at the full voltage.

Again, I probably need to look at the schematics a little more, but if anyone has a little info on this, that would be helpful.
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Re: Otari MX-5050 Restoration Thread

Postby twelvepoint on Fri Oct 31, 2014 8:56 am

Brief update: I sent the roller out to Terry this week to get recovered. It was only $40, which seems cheap, and it's $40 for any size you send. I remember rollers used to be hundreds to replace on a big 2" machine.

One thing I'm having a problem with is locating the pinout on the power harness. It's some weird Japanese connector that isn't numbered, and from what I can tell, the numbering in the connector isn't in this predictable row/column scheme. I dunno. I'll post some photos and some more info about the connector in a day or two and maybe someone here can help.
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Re: Otari MX-5050 Restoration Thread

Postby twelvepoint on Fri Nov 21, 2014 9:15 am

Another quick update on this:
I got a reconditioned roller back and it looks great.

I was going to try rolling some tape, but although I have some 1/2" 8 track multitrack reels, I didn't seem to have a takeup reel, so I had to get one from eBay, at twice the price I thought I'd pay.

I'm pretty much ready to try it out, except I'm not 100% that every supply voltage is working, and my harness is a bit of a mystery.

Close as I can tell, the power harness that goes to the modules is a Japanese equivalent of a Cinch Jones "310" type 10 pin connector like so:
Image
I am having a really hard time finding pinout info on this connector! It's making checking voltages a pain.

I'll post some photos or a video when I'm able to roll some tape through.
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Re: Otari MX-5050 Restoration Thread

Postby elisavage on Sun Mar 01, 2015 10:59 pm

I nearly cried when I found this thread for the restoration of an Otari MX505 8 SHD.

I picked one up a few years ago without the power connector for the preamps (the cinch jones 10 pin cable) I spent so much time trawling the forums trying to find a pinout because acquiring an original cable seemed unlikely. I even found a copy of the manual with schematics and blown up build instructions, but there was nothing about that pinout. If you get this figured out I would be ETERNALLY grateful if you could share it.

Thanks,
Eli

And great job so far!
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Re: Otari MX-5050 Restoration Thread

Postby elisavage on Tue Mar 03, 2015 10:09 pm

I also have a manual with schematics that I can copy for you if you need that.
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Re: Otari MX-5050 Restoration Thread

Postby Adam Smith on Fri Mar 20, 2015 9:57 am

These usually have the light purple panasonic caps that, by now, are leaking. I just re-capped one and in some cases the leaking caps had corroded the PCBs. If you are having power rail problems, you might want to look around for corroded traces near caps. I strongly suggest re-capping it ASAP. The audio cards aren't too bad, but there are seven caps on the audio motherboards that need replaced too and you have to carefully remove the board, you can't do it with the board mounted, its a pain.
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Re: Otari MX-5050 Restoration Thread

Postby ludwighart on Wed Mar 16, 2016 6:24 pm

Great to follow!

I'm a reel to reel fan from Sweden who just got my hand on a MX-5050 8SHD, is there any chance anyone of you could help me out sharing your manual and schematics?

Send me a message her or to my email (ludwighartmusic@gmail.com).

It would be too great!

Best, L
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Re: Otari MX-5050 Restoration Thread

Postby GaryV on Mon Jan 29, 2018 6:26 pm

Hi,
I have a MX 5050 2 SHTD.
Having trouble rounding up tech data. My Capstan motor won't run. Cleaned all the switches, no signs of Corrosion on the boards. I would like to check voltages to the motor, but I can't find stats. Any ideas?
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Re: Otari MX-5050 Restoration Thread

Postby tmoneygetpaid on Wed Jan 31, 2018 4:23 pm

Did you find this post on google?

"Oh... THAT is a minipro.

Yeah, good luck with that one. NOT AT ALL like the 5050MKI to III

This deck is built like a Teac A series and uses a plain induction motor. Simple and AC driven.

Check the micro switch(es) on the take up tension arm. They can go open and the capstan won't spin.

This IS a good deck, but you won't find any info on it.

BTW, it is a very rare deck, so it would be great to fix it. "

Also, looks like Hifi Engine has a maintenance manual and schematics if you just search MX5050. The 2SHD, if I'm remembering correctly, will be lumped in with the 2SH. I can't remember what the letters mean, but if I understand they designate the type of headstack.
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Re: Otari MX-5050 Restoration Thread

Postby tmoneygetpaid on Wed Jan 31, 2018 4:42 pm

Also apparently the very oldest versions of the first MX5050s had belts, so check that there isn't a broken belt or the goopy remnants of one inside.
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Re: Otari MX-5050 Restoration Thread

Postby GaryV on Thu Feb 01, 2018 12:27 am

Thanks for replying. My machine does not have belts. It has a servo motor. I will check the switches tomorrow. Is it better to approach them from the front or back?
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Re: Otari MX-5050 Restoration Thread

Postby twelvepoint on Thu Feb 01, 2018 7:15 am

For some reason I didn't see the old replies to this until the thread was recently revived. Anyway, I did manage to find the power issue - there was a broken circuit trace on one of the power boards and now the machine seems to run ok. I've wanted to get an MRL tape and calibrate it properly, but I haven't been able to justify dropping a couple bills on a machine I won't be using right away. I We recently moved and the machine is boxed up but once I get my shop in order I'll unpack it and take some photos and see where I left off. Yikes, it's crazy that it's been over 3 years since I last touched this machine!
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Re: Otari MX-5050 Restoration Thread

Postby tmoneygetpaid on Thu Feb 01, 2018 10:56 am

GaryV wrote:Thanks for replying. My machine does not have belts. It has a servo motor. I will check the switches tomorrow. Is it better to approach them from the front or back?


Not sure- you should check out the manual on HiFi Engine and see if it details how to get to those switches. If not, I'd remove the tension arm(s) and see if you can access the switch(es).

I had an MX5050 8-track, and when the tension arm swung out to a certain point in its rotation, the capstan would start spinning. So that's what you're trying to get to happen, and the guy who posted above suggested that those switches fail open. To test that it is, indeed, the switch, you could bypass the switch by directly connecting whatever's on either end of it (ie whatever connection the switch makes when it's "on" just momentarily connect manually) to see if the capstan starts spinning.

The manual has a few different suggestions for things that may cause the capstan to not start, I've attached a shot of that bit of the manual.
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Screen Shot 2018-02-01 at 9.48.19 AM.png
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