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Author Topic: Otari MX5050 BII repair questions  (Read 18488 times)

Offline miroslav

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Re: Otari MX5050 BII repair questions
« Reply #15 on: July 02, 2009, 10:53:41 PM »
Yes...I knew about all the Record switches...they were all lighting up when engaged, etc.

BUT I HAVE GOOD NEWS!!!

I removed the head block, and ran some continuity tests on the heads, and also checked some of the wiring on the head PCB and on down to the main REC AMP PCB...and during that process, something shifted, and now I can record on both channels!!!
I will still need to locate the cause...though it's looking more and more like just a bad connection or a cold/intermittent solder joint along the path I was checking...though it could also be somewhere else, since I had to move the PCBs around to get inside, and something moved somewhere.
At least I think I've ruled out bad heads or bad switches or blown electronics...now I just have to find the bad connection and fix it so it stay good.
But I made it this far, though I got a migraine staring at the schematics...they could have made them even smaller! ;-)

Now for the next step?
I'm going to throw on a reel of tape, put it in Record, and them gently tap/move/pull on some of the wires/connections while watching the Left VU meter.
Hopefully, I will find the bad connection easy enough...and HEY, so far I haven't broken anything during the process or lost any of the screws! (I'm going to keep my fingers crossed.)  :-D

I should have it sorted out and all back together sometime tomorrow afternoon and I hope to be recording some music by the early evening.

OK...so a couple of days troubleshooting down the drain?but it should be an easy fix in the end, and best of all, no need to take it in for major service, though I still have to check the electronics/calibration, and I don?t have a test tape for it yet, so I?m hoping everything is pretty much spot on and I won?t need to get that serviced, though I won?t care if it has to go in for that, at least the deck is not broken in a bad way like I first thought.

When I locate the source of the problem...I will post back for sure.







Offline ironbut

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Re: Otari MX5050 BII repair questions
« Reply #16 on: July 03, 2009, 02:46:25 AM »
Good deal Miroslav!
I think that edge connectors on one of the boards or multipin connectors to the boards are the usual suspects. One of the drawbacks of a machines lack of use is that oxidation goes unchecked and just moving it a little will scrape a clean connection through the oxidation or whatever happens to be floating around in the air.
If you have the time and patience, it's not a bad idea to pull and replace each multipin a couple of times.
 Having a girlfriend or spouse with tiny hands really comes in handy sometimes. I know that's what I look for in a woman!
steve koto
 Sony scd 777es(R. Kern mods)> Vpi Aires>Dynavector XX-2mkll>Bent mu>CAT ultimate>CJ premeir 140>Magnepan 1.6qr(Jensen xover)Headphone Eddie Current Zana Deux>AT ad2000,HD800 ,Metric Halo ULN-2 (battery powered),
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Offline miroslav

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Re: Otari MX5050 BII repair questions
« Reply #17 on: July 03, 2009, 10:05:45 AM »
I found the culprit!

It wasn't a loose wire or multi-pin connector...it was one of the aluminum electrolytic capacitors that come right before the two relays and the multi-pin connector that feeds the Erase and Record heads.

I was moving the multi-pin connector back and forth, and noticed the Left channel would drop out at times...but it didn't seem to be in sync with my movements of the connector. Then I realized I was brushing my finger against two capacitors (one for the Left channel and the other for the Right).
When I focused on moving them instead of the connector, I quickly found the problem. I guess my fat fingers worked for me this time! :-D
As it turned out...one leg of the capacitor of the Left channel was never properly soldered to the board. It didn't come loose during shipping or break off or cold soldered...it was just NEVER soldered!
It had managed to j-u-s-t make contact with the board, so I bet that's how it passed QC at the factory.
It took me about 2 minutes to fix it once I found it.

I am now of the belief that it is because of this capacitor that I ended with this 5050 in my possession and in this almost-new condition.
My thinking is that the radio station where it came from, probably put it into service and they quickly discovered the Left channel problem. I think someone must have tried to find/fix it, because when I got the deck, all the screws on the access panels were kind of loose, like someone had opened them to look inside, but never screwed them back on tightly. Maybe they were planning to get back to it at some point and so they just left the panels on loose...?
The radio station probably had other decks...so once the problem was discovered with this one, it might have been put back in the stock room for a later repair date because of work schedules or whatnot, and then the radio station closed down...and so the deck never really got repaired or used.

It seems to me like that's what happened now that I put all the pieces of this mystery together. I guess I should be happy that they messed up at the factory, because I ended up with an almost-new deck thanks of a single missed solder joint!!!
Now that I fixed the problem, I think I can gloat just a little and say that this deck only cost me about $550 w/shipping?and they guy who sold it to me, also found the brand-new, in the box w/plastic, remote control for the deck?which I also just purchased for $60.
All in all, not a bad deal for a deck that costs about $6000 new and a remote that costs about $400 new!

Thanks to everyone?s ideas/suggestions! They kept me motivated to look for the problem, since I was finding it hard to believe that a deck in this clean/unused condition would have anything seriously wrong with it. I was really convinced it had to be something minor?like a bad connection.
Today I will put it through its paces and see if the calibration electronics need any tweaking?hopefully they won?t, but I would not be too disappointed if I had to take it in to JRF Magnetics for basic set-up/alignment because I know now that deck is healthy.

Miroslav

Offline ironbut

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Re: Otari MX5050 BII repair questions
« Reply #18 on: July 03, 2009, 11:11:30 AM »
Wow! Great success story.

Have fun with your new machine and you have every right to brag about the deal you got!
steve koto
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Offline steveidosound

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Re: Otari MX5050 BII repair questions
« Reply #19 on: July 04, 2009, 01:47:58 AM »
Great job tracking it down and a great story. So glad you got an almost new machine.

Some of us are not so fortunate. I had been wanting a reasonably compact 2 track stereo, 15 ips. 10.5" reel machine from the tube days.
I found a last generation tube Magnecord 1028 made in 1969, 2 owner, documentation from the original owner, all reel hold downs, Balanced XLR mic. and output transformers installed and looking as if it had been little used.
 Well, I have (so far) in an attempt to get it working, found a bad capacitor solder connection on one channel that seems to have been barely soldered - somewhat like your problem, but also an intermittent connection somewhere around the bias trap coil in the other channel, an open channel in the otherwise unworn 2 track playback head, which JRF just replaced for me, (the 1/4 track play head and the record and erase are OK). I still can't seem to figure out why it doesn't want to erase on one channel and despite lubrication the capstan motor (similar to that in an Ampex 350) is making noises like I might have to replace it's bearings. Most of this was caused by extremely rough handling is shipment unfortunately. So rough it actually dented the heavy steel outer case. I guess I should be happy that it seems to have very little hum, the transport handles tape very well and on the inside it is virtually cosmetically perfect.
Steve Williams

you don't want to know what equipment I listen to...

Offline miroslav

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Re: Otari MX5050 BII repair questions
« Reply #20 on: July 04, 2009, 09:22:43 AM »
Most of this was caused by extremely rough handling is shipment unfortunately. So rough it actually dented the heavy steel outer case.

That kind of stuff just makes me so mad!
Were you able to recoup and $$$ from the shipping company...was it insured?

A couple of years ago a purchased a deck mainly to use as a spare/parts machine. I was interested in the motors, the head block...etc.
Well...FedEx must have dropped it down a flight of stairs...and then, they must have replaced the exterior box to cover up the damage. It was just a thin, flimsy cardboard box?with a 75lb deck inside!
When I opened the box...the front face of the machine was completely sheared off!
The rest of the deck was beat up all around. There was nothing I could salvage AFA the transport/reels/head...it's like they were never there. And I know it had to be FedEx that replaced the box, because there were none of the broken parts inside?!
I saw pictures of the deck from the shipper (a music store) before it went out...and the deck looked fine.
I was able to get a full refund from the store...but I was very mad to see that happen to a R2R that could have still lived on.

Well...it sounds like you have your work cut out for you in getting that back to full operation (a lot more than I had to deal with). I can't give you any suggestions on the capstan motor...sounds like the deck got beat up pretty bad.
What a shame. :(

Good luck!

Miroslav

Offline Indyguy

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Re: Otari MX5050 BII repair questions
« Reply #21 on: July 06, 2009, 07:01:04 PM »
Hi miroslav - what a great story!  Sounds like in the end you ended up with a pretty sweet deal - congrats!  I hear you about those schematics though - very small!  I have mine on pdf so I can blow them up on the computer for these old eyes.  The rewind/ff issue is still intermittent on my 5050bII, so I suspect an edge connector.  I was trying to locate the likely culprit from the schematics, but I may just take ironbut's advice and pull each one a couple of times to see if that works it in.  Trying to do this low budget, so learning as I go.  Man these Otari's are built nice - very easy to access everything!  I'll keep the group posted if I find the right connector!  Jim

Offline ed

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Re: Otari MX5050 BII repair questions
« Reply #22 on: February 10, 2012, 08:30:03 PM »
GREAT write-up! I too am having a NO ff/RW situation but fine in PLAY. NOW - thanks to this great post, I know where to focus.

THANK YOU ALL!!

ed

Offline progdrums

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Re: Otari MX5050 BII repair questions
« Reply #23 on: October 08, 2012, 09:16:47 AM »
ED
Get a can of contact cleaner with lubricant and spray out all the switches well as they oxidize and cause alot of problems. This is quite common with otaris, however, they are built from high grade parts and clean up well! The MX5050 had been designed with maintenance in mind and is a pleasure to work on in comparison to other machines of its size.

Offline Listens2tubes

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Re: Otari MX5050 BII repair questions
« Reply #24 on: October 09, 2012, 08:43:03 AM »
Yes cleaning the head and speed switches can fix quite a few odd problems. Also reseating all the plugs on the boards can bring better performance.
Neal - Ampex Fineline F-44, 3 - Otari MX5050BII-2, Revox A77 Mk II , Teac A 4010s, 4070, Sony TC102A, Magnecord 1020, Systemdek IIX/Dynavector Karat 17D2MKII, CEC CD3300 CDP, K Works NanoMax DAC, Van Alsine Transcendence Eight+ tube preamp, Dynaco MkIV amp pair, Paradigm Reference Studio 100 v1

Offline ed

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Re: Otari MX5050 BII repair questions
« Reply #25 on: February 06, 2017, 10:00:56 PM »
WoW - that was awhile ago... have since sent to Gustavo i n P.R. for all work - not even sure which of the 4 MX5050's it was...