Otari Deck Owners

[jcmusic]

How many of you use the SRL switch on your deck? When playing TP tapes does it push your meters into the red alot? Is that just the way they are recorded?

Jay

[joeljoel1947]

The SRL switch bypasses the volume pot on the front so that IN THEORY it should sound better. If your hitting the reds hard in SRL mode, you might even hear some distortion if its bad enough (lights on steady). The adjustment for the SRL level is inside the machine and is set during the calibration process. Better left to a pro if you don't have the equipment pictured below.

I won't have my TP tapes till end of next week so I can't comment how hot they recorded them. As long as the meters don't peg in SRL mode and you don't hear distortion I wouldn't lose sleep. Also, remember, you can just get it out of SRL mode and solve you problem and make the meters any level you'd like with the volume knobs!

http://i251.photobucket.com/albums/gg315/JoelKozlowski_2007/Testequipmentmadness.jpg

[jcmusic]

Hi Joel,
Yes you are correct about getting out of SRL mode, I was just curious as to what others thought about this. The peak lights will come on from time to time, also the meters will get pegged once in a while. I will wait to hear what you expirence when you get your tapes.

Jay

[joeljoel1947]

Well, it's pretty much a crapshoot with regards to the red lights. The red lights mean nothing. Believe it or not, the Otari is so sophistocated you can tell those red lights WHEN to come on and by how much intensity----there are adjustments on the motherboard for that too!

Unless you hear distortion when they are pegged for a few seconds, you are safe and not overloading the output itself. Agian, the red lights mean nothing......

[jcmusic]

Joel I won't argue about the lights, but if they mean nothing why put them there? Are they just for recording? Also I do not hear any distotion at all I was just curious what others thought.

Jay

[joeljoel1947]

I say they only mean nothing because they are all relative. You can make the red lights come on when the meters touch +1dB or you can make them come on when the meters are fully pegged and buried past +3dB. It's your choice!! In other words, its nothing accurate unless you know what you are doing setting the deck up.

The small pots for these adjustments are on the internal motherboards. You can dial those red lights in any way you like. That's why I wouldn't get too hung up on them. You can even dial in the INTENSITY of the lights. Want a flicker at +2dB?? No problem. Want a steady HARD RED at +2dB?? No problem as well!!!

They put them there (the red lights) so that when you have the deck properly calibrated to the tape you are using, you will know what is REALLY red and what is not. You would need a professional calibration using the alignment tape for the Tape project (or another calibration tape) to know for sure.

Not sure that you will get too many responses on this type of thing because you are asking about 1 deck and 1 question. It's going to be a needle in the haystack type of deal. I am so lucky to have Joseph from Award Audio right here next to me in Michigan. Otherwise, I'd be lost in Otari-land. This guy knows more then Otari themselves about these decks. Not even joking----, I wish I was!!!! :-)<-

If you hear no distortion, you are fine. Again, don't worry what the meters are telling you, they are relative and mean (probably) nothing!!!!

[jcmusic]

OK Joel sounds good to me, thats good to know about the meters. The next time my decks needs attention I will get the meters set the way I want them.

Jay

[Joseph L]

Of course your right Joel, The led's can be set for a wide range of peak output level. From the manual specs they should light at about +16db with 250nwb (+3) tape. The VU meters are calibrated relative to the tape in use so you know what level you are getting on the tape when you record. On a pro machine, like the Otari,when you are playing a calibration tape with a 1khz tone at the reference level (i.e. 250nwb), you should see +4db at the outputs. On a consumer machine you would see -10db at the output. This is because pro level output is hotter than consumer level. Here is where all the db levels and VU meter readings become confusing, you have to separate in your mind that db on tape, db at machine output and VU may all be different or perhaps not. To add to the confusion there are different names used for the same thing i.e. dBm, dBv, db and VU which may equal any or one of these. Yes I know, two confusing and contradictory sentences, well that is the problem!

Ok, what is 0db (dBm) in audio context? For audio purposes and in reference to tape machines a db or dBm or dBu would equal the reference voltage of 0.775 RMS ("root mean square" don't worry about what this means it is simply a way a tester reads voltage and you need a RMS tester to come up with this reading). Using this as a reference voltage, +4db would equal 1.23v. It is standard practice that when a machine's VU meters read "0" the output will be either the pro level of +4db or the consumer level of -10db.

addendum: Jay Pemberton has pointed out that..."The -10 level is referenced to 1 volt, not to .775 volt (which was one milliwatt into 600 ohms). As the difference between .775 volt and 1 volt is 2.2 dB, the actual difference between the -10 and +4 levels is 11.8 dB." Thank you Jay!
Now lets define tape db, Tape is made with different densities of iron oxide (magnetic particles) expressed in "nWbm" (nanowebers per meter) each increase in density allows the tape to output more voltage (flux) from the magnetic head before the tape becomes saturated. The first commonly used tape was 185nwb which was called 0db tape because when this tape is played on a properly calibrated machine it should output 0db. But in this case "0db" could simply be said to be "0" or standard reference level. Because on a pro machine this would really be +4db at the output and -10db on a consumer machine. In all cases however, when a machine is calibrated for a specific tape i.e 0db, +3db, +6db, or +9db, it will read 0VU on the meters and output either +4 or -10db when the 1Khz reference level tone is played from the tape. Now when a machine has been calibrated for 0db tape and then one that is higher in level, i.e. +3, is played on the same machine it would in turn read +3VU and the voltage at the machine output would be +3db hotter, that is +7db or 1.7v on a pro machine. ARE WE CONFUSED YET?

So now if you are following this, since most tape used is +3 +6 or +9 you can calibrate your machine for one of these tapes so that when you record you can set your level for an average peak level of 0VU and take advantage of the tape's higher magnetic density. This would then mean that when you play a reference level tone, on whatever tape the machine was set for, your VU meters will still read "0VU". Again this would mean that on a machine calibrated for +6db tape the VU meter will read 0VU at the reference level tone. So now you can see that if you played a 0db tape on the +6db calibrated machine it would read -6VU. If you understand this you can see that depending on how the machine is setup the meters may peg all the time or read low depending on the setup and the level tape that you are playing.

What this all boils down to is, that what the VU meters are showing may or may not indicate any distortion and are only a gauge for the tape level when calibrated for a given tape. The rating of tape i.e. 0db +3db +6db and +9db are the relative amount of magnetic flux that each tape can accommodate without going into saturation. The actual saturation level of the tape is higher so the tape can easily accommodate peaks above the rated flux but the rating is for the average peak level with a low percentage of distortion. At any given calibration the referance level should read 0VU and the output should be +4db or -10db depending on the designed output level of the machine. Further more since the VU meters are set up during calibration to the tape flux, if they are pegging or are always in the red this does not necessarily mean that the machines electronics or the tape are even close to distortion. On the Otari machines the red peak led is put there to give you an indication when you are truly nearing the real saturation point of the tape but is only helpful when using the same flux level of tape that the machine was calibrated for.

It took me sometime to wrap my mind around this all but after reading much information over and over and doing my own calibrations it finally sunk in. I hope this is helpful in understanding this whole db thing! If I have made errors in my explanation my apologies and please point it out.

Joseph L

[joeljoel1947]

ARE WE CONFUSED YET?


YES!!!!! :confused:

Seriously though, I do understand most of what you wrote. As you state, it is easy to get mixed up even if you know what your doing with all the variables involved. And, if I read your post a few more times I may actually "get-it"!

Thanks for taking the time to explain the behind the scenes on what my MUCH more meager and simplistic explaination was. It's good to have you on this board for your technical knowledge!!! Here is us giving you praise:

*praise*

[jcmusic]

Well no Joseph, that explaination pretty well sums it up. I was just curious to know if anyone else was expirenceing the same thing I was. Thanks so very much for your time.

Jay

[Jay Pemberton]

The only goofs I spotted are, the original reference fluxivity level was 185 nWb/m, not 180. The -10 level is referenced to 1 volt, not to .775 volt (which was one milliwatt into 600 ohms). As the difference between .775 volt and 1 volt is 2.2 dB, the actual difference between the -10 and +4 levels is 11.8 dB.

[Joseph L]

Thank you Jay for the corrections. I have noted them in my post.

[Manalog]

Hey Joseph L,

Excellent, excellent post!

You've pushed me a little closer toward that light bulb going off where I finally 'get it'. I'm not there yet, but I can feel it slowly falling into place. And I know it's pretty straight forward once it 'clicks'.

We need more posts like this. Just great!! *reelspin**reelspin**reelspin*

[Doug_Olitsky]

Reading all that is most interesting!!!.

As a DIY kind of person I uasually do all this stuff myself but in this case, as a new RtR owner, I think I'm glad I had the first cal. performed on my Otari performed by a pro.

In the future if I wanted to do my own cal. what tools would I need?

I have the the following...
RMS DMM
O-scope
Freq gen. / anaylsis software - Visual Analyser http://www.sillanumsoft.org/

I dont have MRL tapes, and after reading how they are made I can see why they are pricey. Here is some reading on these tapes... worth reading. They are too big to post so here are the links...

http://home.flash.net/~mrltapes/choo&u.pdf
http://home.flash.net/~mrltapes/pub101.pdf

BTW- I have scanned and created a COMPLETE, annotated, service manual, in pdf for the Otari mx5050BII2, including all schematics and diagrams. If anybody is interested.

It's big (80mb) too big to e-mail or post. Perhaps we could set it up as a sticky and then it could be removed form the site if Des finds that it is taking up too much room on the server. Or perhaps somebody else has a better idea for making it accessable for those interested in it.

[Joseph L]

I think you are all set Doug it looks like you have everything you need except the MRL tape.

I know that you asked the question before without getting any response but it is possible to make a calibration tape from a well aligned machine for use in tuning up another badly out of adjustment machine. With the understanding that any errors in the machine used to make the tape will only be magnified later and your tape will of course be multi track instead of mono like the MRL tape. But if you do not have a MRL tape and want to fool around with another machine you could run a set of tones on your machine that is in alignment with your frequency generator software.

This is in effect what often is done in the studio where a set of "Tones" are run on a recording so that later the engineer can adjust his machine to match the original for playback. The TP project people are also providing something similar with their alignment tape.You will not have any set reference to go back to or to check out the "source" machine but it can be useful to get a second machine close.

Be warned that in addition to all the normal pitfalls, making your own tape creates another potential slew but it can be good for learning, especially if you have a deck that you can "sacrifice" in this way. I would make tones for 30hz, 100hz, 500hz, 1KHz, 8KHz, 12Khz and 16Khz. Be sure to set output and input levels carefully especially track to track.

[jcmusic]

Hi Joseph,
Can you tell me about a possible mod to electronic's specificly the output side of the Otari MX-5050 BII to improve the sound quality? I am trying to keep the deck as stock looking as I can with the best sound.

Jay

[Joseph L]

Hi Jay,

There are several others that are looking at doing upgrades as well. I do not have any circuit improvement or parts upgrade ideas on the Otari currently. If I hear from someone about such mods I will share it if I can. I will say that I plan to test out a Bottle Head head amp soon which may be the best approach at improving the playback side and not excessively expensive if you build it yourself. There are some ICs in the Otari and lots of switching transistors etc. An outboard amp of some kind likely would be the better way to go to make major sound improvement. I have just wired RCAs on a BII direct to the card edge connector on the head block. I will try to post some of those pictures soon.

[ecir40]

BTW- I have scanned and created a COMPLETE, annotated, service manual, in pdf for the Otari mx5050BII2, including all schematics and diagrams. If anybody is interested.

Jay, I think I have read somewhere in the forum that Doug is looking into this and he has the schematics.

Doug, I have to imagine the schematic section is quite large but small enough that if just that section is scanned, emailed copies can be floated around for others to evaluate possibe upgrades or of which caps would need to be replaced due to the age of this deck. Then screenshots could be posted of the section of the schematics that would be involved.

I have just wired RCAs on a BII direct to the card edge connector on the head block. I will try to post some of those pictures soon.

Pics would be great!!! Maybe Joel has some too.

Thanks, Brad

[jcmusic]

Quote:
Originally Posted by Joseph L
I have just wired RCAs on a BII direct to the card edge connector on the head block. I will try to post some of those pictures soon.

Joseph would this be just for playback? Or would this cancel any recording options?

Jay

[joeljoel1947]

Hi Jay,
It won't interfere with the recording aspect of the machine at all. The head out wiring just affects (and improves) the playback from the machine. Here is a video below Joseph made of my Otari console deck that is interesting. The big thing with these decks (like any low-level signal source such as MM/MC carts) as trying to fix in this video. In the video,you can see that he did! *Hi5*

In the video, as a test he runs the deck over to his mixer as an amplifying stage to test. The Bottlehead will be here tomorrow to do the final testing.

My Bottlehead is due back tomorrow,from them,with new options, so I'll be dropping it by Joseph's to make sure it functions "hum-free" with the connections he's made:

http://s251.photobucket.com/albums/gg315/JoelKozlowski_2007/?action=view&current=P1020544.flv

[bobschneider]

I have a copy of the schematic of the audio section of the MX5050B-3 posted at http://home.comcast.net/~bobschneider8/site/?/photos/

I'm looking at doing basic POOGE mods - basically upgrading caps and op amps. I also have an older MX5050B-2HD, that I'm rebuilding the transport as well as upgrading the electronics. In that one, all 3 motors have easily replaceable 608 bearings (1 in the capstan motor, 2 in each hub motor) - I've ordered these replacements http://www.vxb.com/page/bearings/PROD/Kit7951 I suspect that the same bearings work in the later versions of the MX5050, but I haven't yet opened up the B-3 to check.

[ecir40]

Bob, keep us updated with your progress. Pics are always nice along the way. Do you have a copy of the schematic for the power supply?

Thanks

[jcmusic]

I have a copy of the schematic of the audio section of the MX5050B-3 posted at http://home.comcast.net/~bobschneider8/site/?/photos/

I'm looking at doing basic POOGE mods - basically upgrading caps and op amps. I also have an older MX5050B-2HD, that I'm rebuilding the transport as well as upgrading the electronics. In that one, all 3 motors have easily replaceable 608 bearings (1 in the capstan motor, 2 in each hub motor) - I've ordered these replacements http://www.vxb.com/page/bearings/PROD/Kit7951 I suspect that the same bearings work in the later versions of the MX5050, but I haven't yet opened up the B-3 to check.
Well Bob how about an update and or some pic's?

Jay

[bobschneider]

I'm doing the B-2HD first, to get some experience before I tackle the B-III. I'm still waiting for a few parts. The caps I need just turned up today. I've ordered some replacements for mechanical wear parts from Otari (tape guides, etc), but those have to come from Japan, so they'll be a couple of weeks. Right now the clean up is basically done, and I've begun the mechanical rebuild. I expect that, with work, vacation, etc, it'll be a month or so before I get her up and running.

I'll try to take a few photos of what I've done to date and post them.

[jcmusic]

I have a copy of the schematic of the audio section of the MX5050B-3 posted at http://home.comcast.net/~bobschneider8/site/?/photos/

I'm looking at doing basic POOGE mods - basically upgrading caps and op amps. I also have an older MX5050B-2HD, that I'm rebuilding the transport as well as upgrading the electronics. In that one, all 3 motors have easily replaceable 608 bearings (1 in the capstan motor, 2 in each hub motor) - I've ordered these replacements http://www.vxb.com/page/bearings/PROD/Kit7951 I suspect that the same bearings work in the later versions of the MX5050, but I haven't yet opened up the B-3 to check.
Bob still waiting to hear from you on this.

Jay

[Doug_Olitsky]

I do have the complete manual in PDF. I'm happy to share, the only issue is the complete file is like 80mb.

If somebody has the space I can e-mail it or we sould set up a remote assist request (xp pro) If you send a remote assist once established files can be sent directly to your computer.

I'd be interested in a audio path up grade of the 'lytic caps and OP amps of my BII2. if anybody know which they are.

(nice thing about my McINtosh gear is that they hilite the audio path in the circuit.

[bobschneider]

I'd be interested in a audio path up grade of the 'lytic caps and OP amps of my BII2. if anybody know which they are. .

Hi, Doug. I traced the audio paths on the BIII schematics you sent me. It wasn't too tough - for the playback path, I traced from the output to the head, and for the record I traced from the head to the input.

In the BIII, the key Channel 1 playback path coupling caps are C133, C134, C129, C122, C119 and C117. For Channel 2, the numbers are in the C200 series, with the same last two digits. That's 4 10uF and 2 33uF caps per channel. I'm replacing these with bipolar Blackgates, but bipolar Nichicon Muses would be almost as good, and a lot cheaper. You probably also want to upgrade C101, C104 and C107 - I'll use bipolar Muses for these.

The op amps in the playback audio path are IC101, IC102 and IC501. I'll likely use OPA2134s for these, at least for a start, since I have a lot of these I bought for another project but didn't use.

In the record path, the key caps are C317, C314, C311, C310, C309, C306 and C305 (plus C301, C302, C322 and C304 if you're going to use the mic inputs). The opamps are IC302, IC505, and IC504 (plus IC402 for the other channel, and IC301/401 for the mic inputs).

I also plan on upgrading the power supply caps on both the audio board and the control board (where the main PS is), with Panasonic caps from Digikey and/or Muse caps from Handmade Electronics, and all the caps on the Capstan Driver pcb. The schematic isn't in the service manual, but in my B-2HD the caps are 100uf/10V; 100uF/35V; 33uF/16V; 22uF/35V; 22uF/16V bipolar; 4.7uF/35V; and 10uF/16V - there are 3 of the 10uFs, and one of each of the others.

[ecir40]

Nice job, thanks for sharing.

[Doug_Olitsky]

Bob;

Thanks for the legwork on digging thru the schematic, I'm gonna open it up and look around a bit and see what's lurking in my BII2

[jcmusic]

I would suspect and hope the two would be alot alike.

Jay

[kevinkr]

I have an Otari MX-55-T-M with the time code option and was wondering whether or not the heads have the standard 2 track geometry or if one track is slightly offset relative to the standard?

Reason I ask is that I have a pair of standard 2 track pre-recorded tapes where the left channel does not play back properly on the Otari. The tape itself might be bad.

Tapes recorded and played back on the Otari are just fine.

An Otari recorded tape played on my partially restored ReVox G36 has a problem on the left channel which might be the deck electronics, but the evidence is not yet there to support that. (Heading towards a bad head conclusion...) I did a lot of additional work on the ReVox last night, but have not retested to see whether that helped.

I have not yet played back the pre-recorded tape on the ReVox, but plan to just to see what happens.

So does anyone know where the time code is recorded and whether or not Otari heads are fully compatible with conventional 2 track (half track) as I had (naively and thoughtlessly) assumed?

[MacGyver]

i'm quite certain that i have never been an OTARI owner, but i DO know that i was once an ATARI owner. i hope that counts me in...

[kevinkr]

i'm quite certain that i have never been an OTARI owner, but i DO know that i was once an ATARI owner. i hope that counts me in...


Funny thing is that the price of admission into the Otari club can be quite low, and these decks are rather nice.

We still have a couple of Atari game consoles stashed in the basement.. *idea*

[bobschneider]

Well, I finally opened up the MX-5050B-3 this weekend. All I've done thus far are mechnical upgrades, basically just replacing the wear parts with the new ones I bought from Otari. (The old ones, which are in decent shape, will go into my B-2HD if they fit, since those parts in the older deck were really and truly shot.) I did try replacing the bearings in the motors. The reel motors took 608 bearings, same as the B-2HD. But the capstan motor is completely different in the newer deck, and wants 2 629 bearings. These seem to be a lot harder to find than the 608s, presumably because the 608 seems to be the standard size for skateboards, so there are tons of different ones available. For the 629s, the only ones I've been able to find online are either $3 standard grade or $100 all ceramic ones. I'd rather just get the $10 types I got for the 608s, but if I have to I may break down and get the pricey ones for the capstan.

While I haven't yet done anything to the electronics in the B3, I did notice that they were quite a bit different than the B-2HD. The capstan electronics are part of the main control PCB, rather than a separate board as in the older deck. I did notice that the newer deck was full of Nichicon caps, and most of those on the audio board were bipolar Muses! It looks like I won't be doing a lot of cap replacements, although I'll install the Blackgates in the critical spots in the audio paths, since I already have them. I may also replace some of the smaller electrolytics with the compact Wima film caps Mouser sells (I already have those as well), and I'll upgrade the op amps and install a direct head out, but that'll be about it.

The caps in the B-2HD weren't nearly as good, and were obviously a lot older, so I ended up replacing every electrolytic in the entire deck in that one.

I also noted that the B-2HD used transformers to generate the balanced outputs - I'm going to try bypassing those to a pair of single ended RCAs. The B3 generates the balanced outs electronically - I'll leave those alone and use a balanced to unbalanced cable on the outputs.

[kevinkr]

Interesting Bob, I noted many of the same things electronically speaking in my 1989 vintage MX-55-T-M, lots of Nichicon electrolytics, and Nichicon Muse in the audio path.

I have a manual, but no schematics for my deck. Eventually I will have to look around for that information as I would like to upgrade some of the op-amps in key locations and possibly add a PB head direct out for an external pre-amplifier.

[ecir40]

Thanks for the feedback Bob, good stuff. Do you know what year B3 you have?

[bobschneider]

My B3 is a 1997 model, my B-2HD is from 1980

[Sonichermit]

Mr. Olitsky,
I have the Otari MX5050BII2. I have what is titled the "Instruction Manual" which I believe is simply the owners manual with schematics and diagrams etc. Problem is mine is missing several pages. Pages 8-6, 8-7, 8-8, and 8-9. In fact it may be missing some other things as well. These pages contain parts lists and numbers or possible diagrams or schematics.
I realized this recently as my machine is not running right now. The supply reel motor is not firing up so I have been poking around trying to figure out what is wrong. I am no electronics expert and have only basic knowledge. I suspect several things. One would be a relay or relays, another would be one or more of the dual diodes or it could even be resistors.
Doing voltage readings in a variety of points on the control board I am seeing voltage where none is supposed to be present. In this case I am referring to U5, U6 and U8 which are supposed to be 0V but all three are showing voltage. My worst fear is that the transformer may have some issues. I have yet to check that out. By the way anyone out there who knows the proper procedure for testing a relay with a multimeter feel free to share that info.
Initially I thought it was the motor start capacitor but I am doubtful of that now.

So for all of the above reasons if you can send me the manual complete as you mention you have it would be a huge help. As you mentioned though I doubt you can e-mail it as an attachment due to the size constraints. Is there a way to convert it into an Adobe PDF file? Or you could send it as a whole bunch of e-mail attachments but I doubt you want to spend the time doing that.
Also if there is anyone out there who has any hunch on what is going on with this machine feel free to make some comments.
One other thing I did not mention is that when checking at the fuses FS701 through FS 705 voltage shows up when it is supposed to read zero on several of those that correspond to U5, U6 and U8 that is the reason I was wondering about the dual diodes possibly being faulty as the fuses are in direct line with those fuses.
Any info will be appreciated. thanks

[Doug_Olitsky]

I have the manual in pdf and can e-mail it to you.

its 80mb so ill be using one of the sites that will e-mail you when the file is ready for download


email me @...

doug_olitsky "at" yahoo "dot" com

[Sonichermit]

Doug,
Well after messing about with my 5050 for some weeks not being able to get the supply reel motor going I finally discovered the problem. There is a hair line crack near the edge of the control PCB that crosses over a solder track feeding one of the relays. I made a solder repair to the trace and the motor runs beautifully now.
Soon after I put it all back together I connected it to my mixing console in the studio and feed the machine a CD track via the line inputs. The meter response seemed pretty normal. But upon playback of said track I noticed immediately there was a noticeable difference in the out put of channel two, being weaker then channel one. Several days later I also plugged in mics to the mic inputs, recorded some voice and wanted to see if the output was similarly affected. I seemed both channels were putting out about the same going this route.
Does anyone here have any idea of what I should be looking at. I suspect something to do with either the record amp or reproduce amp . Any info will be appreciated.

[Doug_Olitsky]

check the play back head selection switch.


btw- good find on the pcb trace! I had to do the same on a Klipsch Chorus II x-o!!

[Sonichermit]

Doug,

So far the machine is still working other then the output problem I mentioned earlier. Hopefully the trace repair will hold up. Several days ago I did a few other things hoping they will aid in avoiding any further cracking at that point. Hope I did not do something that is a no no. I took a tiny bit of super glue and put it on top of the crack on both sides of the board hoping this might prevent the crack from going any further. In addition I purchased a half dozen tiny rubber washers that I installed under the metal washers that hold the control PCB up. Just figured this gives a bit of a cushion to the PCB and also helps avoid any further cracking due to inadvertently over tightening them.
I will try your suggestion on the head switch and see if it cures the ailment. Are you implying that the switch needs to be in the 2 track position when sending line input?. I am aware that it only records in 2 track and can play back in either 2 or 4.
Finally I noticed some posts on doing some upgrades on these machines. After looking at the record/playback amp section I noticed there are some socketed chips. Are these just logic chips or are they in the audio path in any way? And if so are there chip upgrades that would be worth bothering with and would not tax the power supply?
I had considered doing some recapping in the power section on the control pcb but frankly that usually only results in marginal differences in performance unless the caps are really bad. Any other suggestions for tweaking are very welcome. I love the way the machine sounds. I also have a Teac A3440 that I just went through and got running after quite some time of sitting idle but the Otari totally smokes it in the audio realm. No doubt because it was built for use in broadcast apps. Thanks for all the help I really appreciate it.

[Skywavebe]

Hi Joseph L.
Your explanation was pretty text book and NO 0dB does not always mean reference to 1.0 Volt. It can mean .775 V in the case of dBm or dBu. Tascam uses dBV for its line as that is a reference to 1.0 V. Teac 0 dB=.775V.
The part that may not be clear but only a EE would catch it would be the term Flux as quantitized with Voltage. Flux is measured Gausse if
I remember the Magnetics course I took and I might mention the instructor was a once president of Jefferson Electric. He was the first one to say he doesn't know too much. I think if people understood the ideas you put forth that they would have a pretty good understanding of the whole process of tape recording. I don't make these comments to seem a person with greater
knowledge but I am happy someone wrote this all out instead of me.
However, not all corrections are correct and just don't accept them. Better to have a correction to what I write than to pass on incorrect information to 100 others I say.
The other thing that through my years of repair will testify to is that not all decks- reels, cassette and other are either -10dB or +4 on outputs.
They can be 0dB (.775) or -5 dB, some -10dB and then others +4 or +8.
Sam,

[Doug_Olitsky]

yep, that switch needs to set for 2trk when sending signal to your preamp. I you made a recording on a 4 trk machine then set to the 4 trk position and all will be well.

I have not started tweaking yet, but Joel and the others have.


Hey Joel, et al;

instead of tapping the xlr out's to retrofit RCA's why not tap into the head phone jack?

[Sonichermit]

Doug,

I tried what you suggested tonight after switching the #2 and #3 pns internally so I assume pin 2 is not hot. I recorded a CD track after switching the unit to two track. It definitely seemed to improve the equality of the meter response although I still see a slight difference. I suspect it may be some differences in the meter settings themselves. The only way I can verify that is to run some further tests but I did notice a difference.
Regarding my other question on upgrades etc. and the socketed chips I'll keep following this thread hoping I see some info in that regard.
By the way the machine seems to be recording fairly well as I just tested audibly how close the playback quality was to the original CD track and at least in that regard I am surprised so I assume the heads are in relatively decent shape considering their age. I looked them over several times with a magnifying glass and they do not look too bad visually.
The only other issue right now I need to rectify is that the tape lifters do not lift the tape completely off the head as you can hear the tape on rewind etc. I had it apart last weekend and suspect one of the springs was replaced on the lifter assembly because it definitely seems stronger then the other one that is on that arm. I checked the adjustment on the solenoid arm for tension and at least without using a gauge it seemed OK. I think the stronger spring is keeping the lifter from dropping down all the way which would keep the tape from touching the head.

[braxus]

Keep in mind any tapes you recorded on the Otari with pin 3 hot, which is the stock setting, must be re-recorded again after changing it to pin 2. If you don't your tapes will be out of polarity. Think of it this way. The tape will record what ever polarity the deck is in and it will be fine coming out no matter what pin is hot. Once you switch the pins, the tape is still on the old setting- so it will be off after the pins are switched.

[Doug_Olitsky]

For an Audio IC upgrade use the OPA2132P rather than the OPA2134. The 2134 is the 'budget' IC. Any OP Amp that has 4558s in it will benefit from having those IC upgrades fitted.

Read this thread it has a lot of what you seek


BII2 Upgrades
(http://www.tapeheads.net/showthread.php?t=532)

[Sonichermit]

Doug,

That makes sense. By the way I don't think there are any 4558 IC's. The socketed ones I saw are 4019's. There are also 4560DX's and some 4560's.

[Joseph L]

Thank you Sam for your corrections. Every one should know that you are one, of the last, of a breed, a true analogue engineer. I certainly defer to your expertise and many years as a professional engineer, service man etc.. All should know that you are also a true gentleman and so very generous with your time and helpful information. Your knowledge and vast amount of experience is an irreplaceable asset to all of us in the world of analogue tape. Thank you!

[ecir40]

I copied this from the schematic in the BII manual.

The op amps in the reproduce amp are IC101, IC102, IC103, IC501, IC502 & IC902 but not sure which ones are in the signal path. IC502 is used for the headphones.

I wonder what Otari has for a replacement for these part #'s

BR

[ecir40]

Hi, I have the MX5050BII2 RTR. Doug sent me a copy of the manual awhile back and it has two schematics in it for the record and reproduce amps, they are labeled A10620B & A10680C. Does anyone know which one of the schematics is the right one for my deck?

The only markings on the PCB are

ASSY NO. PB-16EB

and PB9A482D

BR

[ecir40]

FYI, I talked to Taka in the service department with Otari yesterday and he confirmed the A10620B schematic is for the MKII-2 & the A10680C schematic is for the MKII-F. The MKII-F is a full track mono deck.

BR

[ecir40]

I also have an older MX5050B-2HD, that I'm rebuilding the transport as well as upgrading the electronics. In that one, all 3 motors have easily replaceable 608 bearings (1 in the capstan motor, 2 in each hub motor) - I've ordered these replacements http://www.vxb.com/page/bearings/PROD/Kit7951 I suspect that the same bearings work in the later versions of the MX5050, but I haven't yet opened up the B-3 to check.

Hey Bob, I have a noisy bearing in my take motor and took the motor apart and had a look. The bearing isn't wasted but can tell it needs to be replaced.

Did you use a puller to remove them or just heat them to get them off?

I will probably replace them with the link above. Since you replaced yours awhile back, can you give any feedback on your opinion of them?

Brad