Otari MRL and Multimeter

  • Thread starter Thread starter thereelman77
  • Start date Start date
Well....you want the line to be at a 45 degree angle, going up to the right (like the first image on the left, below), that is "in-phase" ....the opposite of what you have in your right side picutre, which appears to be about 180 degerees out-of-phase.




az_tcd4.webp
 
I know what I'm trying to achieve. My point was that I haven't been able to get the line close to being "in-phase". Every time I get close to a 45 degree line, the azimuth line jumps to the 2nd photo I posted (around 180 degrees out of phase). The adjustment screws literally didn't let me go to where I needed to be. I adjusted by looking at the heads and then checking with the o-scope and it was still out of phase.
 
Mmmmmm....I don't know what to tell you anymore. It could be that you are overshooting the screw turns...it's a VERY minor adjustment to go from in-phase to out....but it sounds like you are trying your best, so....?

Not looking to put the blame on you, but you've had some problems with the entire calibration of that deck...and some of it was you not either fully understanding or not following the instructions....then, you also had two sets of instructions and one of them didn't quite match up with your deck, so not all your fault...but my point is that you've had a difficult time throughout, so it's hard for anyone here on the Internet to guesstimate and tell you what/where is actually wrong.

Heck....it could also be that the deck has issues, and some of the calibration is just not possible because the deck is too worn...????

I just don't know what direction to point you in from here....

Is there anyone that you know in your area that has some experience with aligning tape decks?
Maybe you can ask here. Tell us where you are located and see if someone here is close enough to you that they can help you "hands-on" instead of via Internet posts.
If you were close to me....I would tell you to just bring me the deck and let me have a shot at it. Maybe you just got too far in for your first time, and it's just all gone down hill.
I know I said it before....but I'll say it again.....go back to step 1. and just start the whole thing over....BUT...don't do it piecemeal like you've been doing. Find a free weekend and just start the calibration/alignment from the beginning and don't skip anything and don't stop until you get to the end.
If at any step you are doing exactly as you should be...and measurements are way off....STOP...don't go to the next step, it will be cumulative and by the time you get to the end you won't know what you have.

Sorry....wish I could help more...maybe someone else has more suggestions.
For all the time I've spent typing responses, I would rather have just done the calibration for you! It would have been easier. :)
 
I would double-check your oscilloscope connections and settings before turning another screw. It is unusual that you would be able to adjust a two-track deck to be perfectly 180 degrees out of phase, so it sounds like something else is amiss. Given this is an Otari with the unusual pin-3 XLR wiring, it is also possible the output wiring has been wired incorrectly and is resulting in the electronics being out of phase instead of the heads.
 
I will have to check that out...We re-soldered the XLR inputs but not the outs.

You are probably right miroslav it is something that I most likely either partially or fully messed up myself. Once I understood the process better, their seemed to be more issues I found.
I live in Michigan, about 25mins East of Ann Arbor. Of the few electronic shops we have, I called them up and only one shop would work on tape decks for $99 an hour +$99 for an initial look. That isn't a feasible option. If their is anyone who knows of a tape tech or shop that will could be less expensive, chime in.
 
thereelman77 said:
I will have to check that out...We re-soldered the XLR inputs but not the outs.

You are probably right miroslav it is something that I most likely either partially or fully messed up myself. Once I understood the process better, their seemed to be more issues I found.
I live in Michigan, about 25mins East of Ann Arbor. Of the few electronic shops we have, I called them up and only one shop would work on tape decks for $99 an hour +$99 for an initial look. That isn't a feasible option. If their is anyone who knows of a tape tech or shop that will could be less expensive, chime in.
Click to expand...

Do you mean you re-soldered the input XLRs to change them from pin 3 being hot like a standard Otari to pin 2 being hot like modern wiring on other equipment? If so, you have to do the same to the output XLRs. Changing which pin is hot (2 or 3) reverses phase so if you reverse phase at the input you have to reverse phase at the output if you want the whole machine to remain phase consistent like the original design. If you only did the inputs you only did half the job and have turned your Otari into one big phase-reversal switch.
 
Alright, so having checked the forum a week ago we re-soldered and I spent the day working on the tape deck. It seems to have fixed the issue. The phase is working correctly. I couldn't tell you why we assumed the outputs didn't need to be re-wired, but we switched pin 3 to pin 2 and 2 to 3.
 
But I'm curious again. When playing back the MRL tape at 10khz, channel 1 will go to -1.3db VM and channel 2 will go to 4dbVM, while in SEL. REP mode channel 1 will go into -3dbVM and channel 2 will only go to -6dbVM. Does this signify an azimuth error? I am getting a straight 45 degree line from my scope, but I have noticed that everytime I playback my MRL tape, the playback level is slightly different. Please note that I have already sent my 1/4" MRL back to the factory due to a shedding issue, so this is my 2nd MRL tape with this deck. I would assume for the SRL playback it is a slight azimuth issue, but for the SEL. REP I'm not really sure.
And to also note, I demagged and cleaned all the heads and rollers before I commenced all of my calibrations.
 
If your using the VU meters...or checking at the actual output?
 
Checking the actual output, using my multimeter.

I have my multi., scope, oscillator all set up so I can switch between them.

Unless it's an azimuth error, I would have to guess that their is a loss of high frequency on the heads, as earlier stated, due to age....
 
Ok, so hopefully to put this thread to rest soon here, apparently I had not been checking my output level from my oscillator to my tape deck, which was why I could not get the hi freq up to 4dbm. So after thoroughly checking everything, I can say that everything has matched to the +4dbm called for in the manual, playback, hi frequency, EXCEPT my low frequency adj.
The manual says to turn on the low comp switches adjacent to the pots.....Only issue is that I cannot find them. I hope someone could point to me what I should be looking for, I am not seeing any switches with the amplifier opened up.
 
Well...glad you got most of it sorted out......gotta always remember to check them levels at both ends. :)

You talking about LF EQ or LF Compensation adjustment?
 
The instructions are on Pg. 15 of the PDF calibration manual I gave you links to awhile ago.
The diagram of the switches/pots is on Pg 10.

The LF Comp switches SW 101 & 102 and the adjustment pots VR 105 and 205 are right in the middle of the diagram....right below the REC EQ and Level VRs....
 
The only issue is, those instructions don't match my B2-HD model. I don't have as many adjustment pots. The only adjustments that I have, which I adjusted with the MRL were VR 102 and VR 202 15 & 7.5 REP EQ. That's what my model has. SW 101 and 201 are the source/tape switches on my deck.
I found a large switch labeled H & L in the back panel of my unit. When I switched it from H to L however, it didn't do anything when I attempted to adjust the LOW EQ.
 
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