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Author Topic: MX-5050B2HD on the bench today.  (Read 10333 times)

Offline docb

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MX-5050B2HD on the bench today.
« on: November 07, 2008, 07:23:14 PM »
I acquired a well used MX-5050 this week, which brings the total to four sitting on the shelf. I gave this one to Shawn to work with, to get a feel for how they go together and adjust, so we can address the many requests we have for Otari technical help and mods.

This one has needed a lot of TLC, which is perfect because it's making us go through everything and bench its performance in comparison to the properly set up 5050s we have here.

After a few days with the machine I have some observations for the folks who often want me to explain my choice of the Technics over the Otari for our mods. The Otari is definitely easier to get into. It is laid out with the technician in mind, like a pro machine. It looks more hunky inside.

In terms of pulling tape, I have no reservations about my choice of the Technics. Even though the Otari has what looks to be vastly superior brakes, we have found that with our mod the Technics brakes are just about the same performance-wise and possibly even a little easier to fine tune. In terms of tape path friction, once again with our mods the Technics seems to have less of it than the Otari, though the mods make alignment of the tape path more tricky. A stock Otari can fast wind faster than a stock Technics, but our friction mods seem to make the difference a lot smaller. The big fat capstan on the Technics and the rubber of the pinch wheels seem to be of better materials and finish than the Otari.

This particular 5050 was not running with great stability, at first it was drifting like crazy. We ended up attributing most of that to mucked up, grabby brake pads, some to a brake drum that appears to have a slight wobble on the shaft, a pinch wheel that was needing a bit of smoothing, and possibly a wee bit of bearing wear. After we played with all these issues we have shaken out most of the 2-3 sec wow we first saw in the 10 & 15kHz bands of a tone tape. I have not seen a similar wow issue with any of the Technics machines. Some times we see a small drift or wobble on the strobe with a Technics, but it doesn't usually translate to a visible aberration on the scope, so it could be that the strobe markings are a little inconsistent. Of course the Otari doesn't have a strobe on the front, so it's hard to make a comparison.

The head cable inside the Technics is a nice shielded twisted pair. Inside the Otari it is coax. The head block is very easy to yank on a Technics, but not enough harder on an Otari to quibble about.

That's my observations so far. I'm not calling the Technics a vastly superior machine. I'm just observing that the Otari is a good machine, but not particularly superior to the Technics either. I do find the modded Technics to be a better tape handler and to sound smoother than the stock Otari. We will continue to play with the 5050 and try some of the tape path friction reduction techniques we have done on the Technics. If we find anything encouraging we will report our results.



Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline bobschneider

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Re: MX-5050B2HD on the bench today.
« Reply #1 on: November 07, 2008, 10:20:20 PM »
I for one will be very interested in any good mods you come up with.  I have a B2-HD that was also in rough shape, but which now runs well (new wear parts from Otari helped a lot!)  as well as a BIII.

I also just received today a high speed Revox B77 with half track heads, which appears to be in decent shape, although the heads could use a relapping.  Other than it being an NAB deck, it's set up correctly for TP tapes.  I also found some spare B77 audio boards on fleaBay which should be readily modifiable for IEC 15ips (the PCBs are the same per the service manual, so all I have to do is swap out a few resistors and caps).  Is the reason you haven't been recommending Revox just that the high speed half track configuration is hard to find, or is that only part of it?
Bob Schneider

Offline ironbut

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Re: MX-5050B2HD on the bench today.
« Reply #2 on: November 07, 2008, 10:35:08 PM »
This is great news for the the many Otari users among us. Shawn must be getting to be quite the reel to reel tech by now. I wonder if he had that in mind when he was filling out the Bottlehead job ap?
I would like to say that I've noticed the prices of RS1500's seems to have settled back down to just a little more than normal (they were never what I would call cheap). That's certainly not to say that the 5050's can't be a fantastic Tape Project machine. I'm definitely biased (I still just love my Technics) but I'd like to see how far many of the pro-sumer decks can be taken.
On a related note, there's been a glut of pretty nice looking Studers too. Unfortunately my "mad money" has be spent for the year.
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 Kenkirk

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Re: MX-5050B2HD on the bench today.
« Reply #3 on: November 08, 2008, 08:43:29 AM »
I acquired a well used MX-5050 this week, which brings the total to four sitting on the shelf.




I am glad to see you doing this! I would also like to see you get hold of a  new or just about new MX5050 B III and run it through its paces. I too love the older machines and I am really fond of my Teac X2000r, but I still think there is something to be said for a new machine. I would like to see friction reducing tape path mods become available for the Otari's. I don't know if a fully modded Otari MX 5050BIII would be better than what you have done with the Technics, but it would open up more options in affordable reel to reels. It is nice to be able to pick up the phone and order parts from Otari. They are very nice to deal with. But later when I have my paws on 40 or 50 Tape Project albums, I will hunt down a Studer and pay the big bucks.

Thanks again for what you are doing!!!

Ken
Ken Kirkpatrick
Cat Ultimate preamp, Basis Debut Vacuum, Basis Vector tonearm, Urishi,Walker motor drive, Cat JL-1 amps, Sony XA9000Es SACD, Wadia 860,Yamaha CT 7000, Nak Dragon, RX 505, 2 REL Stentor II's, Sonus Faber Amati's, Cardas Golden Cross and Siltec cables, Otari MX 5050 B III, Teac X2000R

Offline docb

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Re: MX-5050B2HD on the bench today.
« Reply #4 on: November 08, 2008, 11:50:00 AM »
Quote
Is the reason you haven't been recommending Revox just that the high speed half track configuration is hard to find, or is that only part of it?

No different reason than not choosing the Otari. The Technics just floated to the top for me. I have a strong preference for constant tension machines over constant torque machines, and I find the isoloop to be very good sounding transport when set up the way it was originally intended, i.e. without the "belt and suspenders" fixed tape guides everywhere. Not to say the Revox isn't a great candidate for TP tapes too. With the difficulty folks seem to have finding competent techs these days, Shawn and I have been talking bit about whether or not we should attempt to take on other types of machines. It complicates things quite a bit in terms of our lab setup, so no decision has been made yet.

Quote
I would also like to see you get hold of a  new or just about new MX5050 B III and run it through its paces.

We'd be happy to evaluate one if anyone wants to send one to us.  A BIII goes for $5900 new. For folks who want a brand new machine it's the only way to go. On the other hand I have seen nice used Nagra Ts selling for around $5500 to $5600 lately. And shoot, there's a Studer A80 for $2K on the bay, that no one has bid on yet with only 20 minutes left. That's a tough market to sell a new machine in. I had hopes that Otari might be more willing to offer a machine for eval and development but that did not come to fruition.

Quote
Shawn must be getting to be quite the reel to reel tech by now.
Yup, he's a very quick study and can nail an alignment pretty easily these days. Naturally at first I worked closely with him on every step. Now I can just take a look at the scope traces and give a listen when he's done.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline jcmusic

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Re: MX-5050B2HD on the bench today.
« Reply #5 on: November 14, 2008, 03:00:26 AM »
This thread is getting better and better, keep up the good work guys.

Jay
Redpoint Model D TT/Soundsmith Sotto Voce Cartridge Otari MX 5050 BII/BH Tube Repro deHavilland Model 222
 Ah Njoe Tjoeb 4000, Rogue Magnum 99, Korneff 45 SET Amp, Klipsch K-Horns Bass Bins/2" Tractrix Horns 2" BMS Drivers, Vintage Tubes.

Offline docb

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Re: MX-5050B2HD on the bench today.
« Reply #6 on: November 14, 2008, 10:01:05 AM »
I posted this last night in a thread about a different machine, so I will repost the info here in this more applicable thread -

We also just finished a full ball bearing on every tape guide mod to a 5050. We will be listening to this with the Tube Repro tomorrow. I had hoped it would be a mod that we could package as a kit. That was the plan until we went to pull the three fixed guides under the head block. Those suckers are glued together with a nasty white Loctite type material that is a total b**ch to get apart. We had to remove each guide assembly with channel locks and a rubber sleeve to protect the finish, then clamp the guide in a vise and use channel locks to take it apart, install a pair of ball bearings and shims, soak the threads in acetone to temporarily soften the thread lock long enough to chase the thread with a SS screw, then soak them again to soften the remaining goo long enough to reassemble the guide before reinstalling it. The thought of giving tech support for that kind of tedious and potentially damaging work is enough to turn me off from writing up a set of instructions. I'll give listening impressions tomorrow. The mods made to the other fixed guides on the machine were listened to one by one and made an audible improvement in terms of resolution so I hope to have positive comments about the fully modded 5050 vs. the stock ones we have here.

I should add, TANSTAAFL*. The ABEC 5 bearings are pretty expensive and two are required at each position because of their narrow width. Thinking out loud, we might consider a setup where the user removes the headblock fixed guides from the chassis and sends them to us to be rebuilt with ball bearings. Then the user could install these reworked guides along with the rest of the mods themselves. This would save the user some money by installing the easy stuff themselves, and save much frustration trying to get those head block guides apart.

* There Ain't No Such Thing As A Free Lunch
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline Ben

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Re: MX-5050B2HD on the bench today.
« Reply #7 on: November 14, 2008, 01:15:50 PM »
If it where not for shipping worries, I would rather send the whole Otari head assembly out to you. One could get new guilds and a new 2 track head put in and the record heads removed ( less friction ).
Set 45,Open baffle speakers,Otari 5050,,Pioneer DV-79AVi DVD/CD/SCAD player

Offline bobschneider

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Re: MX-5050B2HD on the bench today.
« Reply #8 on: November 14, 2008, 02:37:02 PM »
I'd definately be interested in the bearing tape guide mod for the MX-5050, as long as the price isn't too painful.  BMW parts prices would be OK, but Ferrari prices would be tough...
Bob Schneider

Offline Ben

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Re: MX-5050B2HD on the bench today.
« Reply #9 on: November 14, 2008, 02:46:53 PM »
 VW!  :)

Wait a minute ... Japan and Germany for R2R stuff ...
Sounds like a plot by the Axis[1] Country's to take over.

Has there been any mods to the solid state logic on the Otari MX5050
to improve the sound. I'd like to make a remove the switching logic from the record
head and just run the playback head to the pre-amp.
The only I worry about is any leakage current back to the tape head.

[1]However both places still believe good sounding music.   
« Last Edit: November 14, 2008, 02:58:35 PM by Ben »
Set 45,Open baffle speakers,Otari 5050,,Pioneer DV-79AVi DVD/CD/SCAD player

Offline docb

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Re: MX-5050B2HD on the bench today.
« Reply #10 on: November 14, 2008, 03:17:14 PM »
The fixed guides actually remain on the chassis when you remove the head block. The head block screws down to them and the guides are screwed to the chassis at the back end. So one could remove the head block without needing to disturb the guides, and it is actually a separate operation to get the guides off the chassis.

I don't have a clear picture of what pricing would have to be yet. The ball bearings get fairly spendy when you install 12 of them as we have. There may some compromise we can make to keep the costs to a certain price point without losing the bulk of the improvement. We will continue to play with the idea.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline jcmusic

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Re: MX-5050B2HD on the bench today.
« Reply #11 on: November 15, 2008, 02:41:56 AM »
Hi Doc,
That some really good stuff, please keep us informed.

Jay
Redpoint Model D TT/Soundsmith Sotto Voce Cartridge Otari MX 5050 BII/BH Tube Repro deHavilland Model 222
 Ah Njoe Tjoeb 4000, Rogue Magnum 99, Korneff 45 SET Amp, Klipsch K-Horns Bass Bins/2" Tractrix Horns 2" BMS Drivers, Vintage Tubes.

Offline docb

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Re: MX-5050B2HD on the bench today.
« Reply #12 on: November 15, 2008, 11:32:01 AM »
OK, first issue -

with ball bearings throughout we are having some stability issues. It seems like there may need to be a little bit of drag in the tape path to keep the tape in stable contact across the playback heads. What we see is an amplitude bobble on the left channel and what we hear is the treble cutting in and out on the left channel. The tape appears to be traveling OK across the heads visually, so the lifting of the tape must be pretty subtle and the mechanism behind the problem is difficult to spot. We spent way too much time yesterday trying to sort this out by adjusting wrap on the heads, guide positions, brakes, checking bearings, etc.,etc.  Not sure if this particular machine has a separate issue that is creating the problem or if it's entirely the fault of the the mod. We will need to try the mod on another machine or two to get a handle on it.

I have quite a bit of cover art work to complete right now, so it may be a while before we have answers.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline ironbut

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Re: MX-5050B2HD on the bench today.
« Reply #13 on: November 15, 2008, 12:06:43 PM »
If any of the heads have the least bit of grooving and there's room for even a tiny bit of wandering than that would make sense. When a spec of dust can cause an audible drop out even the least little loss of contact would cause loss of signal. I think that any machine will have a tendency for the tape to wander in one direction more than another. I have a grooved 1/4 track head that I have to constantly keep an eye on because oxide collects in the edge of those grooves and can snowball into tape damage if I don't keep it super clean. I believe that if it weren't for the reversing roller (on my Technics,.. doesn't exist on a 5050) that I might have the same symptoms you're talking about on the 1/2 track head. Maybe that's another reason that the flutter roller is between the heads on the Sony Apr series,.. to isolate the heads and effectively shorten the un-supported tape length.
Just a wild guess,.. again!
steve koto
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 HE Audio Jades

Offline Ben

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Re: MX-5050B2HD on the bench today.
« Reply #14 on: November 15, 2008, 12:13:02 PM »
What I would like to see is a rotating spindle on the tension arms. That is where you have the most friction.
Set 45,Open baffle speakers,Otari 5050,,Pioneer DV-79AVi DVD/CD/SCAD player