Tape Project Forum
Tape Machines => Reel to Reel Tape Machines => Topic started by: rowcherumble on January 11, 2010, 10:16:28 PM
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Hello,
I have an Otari MX-5050 UHX reel to reel, which I believe is one of the earlier versions of this model with the separate VU meters and recording devices.
Anyways, I have an issue with this machine hooked up to my system. If I plug in the headphones through the tape recorder's jack, it sounds fine.
However, if I hook it up to what I usually do--through a dbx 128 and then that goes to a preamp, etc.--the sound is very faint. I have to turn the output all the way up to hear the sound.
I've tried bypassing the dbx and doing it direct to the preamp tape loop and it's still the same issue. I've also adjusted the High Low switch at the back to no luck.
I'm currently using XLR to RCA jacks, which I don't believe are balanced. No transformer.
Since it works fine through the headphone jack, I can't imagine the machine has any problems??
Thank you!
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Your Otari XLRs are pin 3 hot. Your XLR-RCA adapter is probably going to pin 2 hot.
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Also, regarding your XLR to RCA cable...If you ground both pins 1 and 2 (with pin 3 hot), you will get 6 db more output.
That being said....if the low-volume defect turns out to be with your deck (like a muting circuit defect), then you don't need to ground pin 2. XLR should have more than enough level to drive an RCA line input.
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Hi rowcherumble (that's a mouthful! BTWwe use our real names on this forum),
Welcome to the forum.
There's a diagram on the wiring scheme for cabling in the owners manual for the regular 5050. If you don't have one already, you can download one for free here;
http://www.analogrules.com/
(not exactly the most user friendly site but the price is right)
I think you'll find it to be a pretty informative manual even if everything isn't exactly the same as your deck. It gives a reasonably understandable explanation of all the controls and adjustments and will certainly help you to learn your machine.
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Ah yes, now I feel a bit silly.
The machine works fine now that I've resoldered the connectors.
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I have another question though.
How does one adjust the tape bias Cal srews on the front?
The manual is rather typically vague in this regard.
Regarding my username, it's a song title from the post-punk band, The Fall. :) As for real names, duly noted.
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There's a pretty good overview of recording adjustments at the site I gave the link to above. Bear in mind that you will need to adjust your playback correctly first and that requires a test tape. Test tapes can be had here;
http://home.comcast.net/~mrltapes/
There is a wealth of information about tape/recorders on this site also.
If you're relatively new to magnetic tape and reel to reel, above the General forum there's a Beginners Guide and Reel to Reel links located in a couple of stickies you might find helpful.
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If your 5050 is like the B2 and B3 models, then pages 4-5 and 4-6 of the B2 manual give quite good step by step instructions for setting bias, recording levels, etc. If you don't have a manual, then AnalogRules.com has a free download. With both 1 kHZ and 10KHZ calibration buttons, you only need a calibration tape if you want to tweak EQ extremely finely. Larry
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Hello,
I've examined the Analog Rules site, and attempted to set bias and EQ on my machine according to their instructions, using their downloaded tones, but nothing happens.
For example, the site instructs you to turn the Bias screw to set the VU meters, but when I do this, the meters do not change their readings.
My machine has Bias Trap. screws on the back along with Monitor Adjust screws. There are also the Bias Cal screws on the front. Turning the Bias Cal screws appears to do nothing for the VU meters.
This machine was apparently last fully serviced in 1987 and not used since so I'd assume things like the heads, Azimuth, etc. were properly aligned.
Thank you.
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It's not clear if you got the playback adjustments dialed in first. Is that all good?
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I believe the playback adjustments should be fine.
Also, I should note that the small SRL light doesn't light up when I switch the Output switch to SRL even though the switch appears to work fine.
I have the machine switched to Low instead of High on the Line Out in the back. The high seemed to have too much gain for my preamp/amp.
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It's normal to have too much output signal since you are using the XLR out into an RCA line input. XLR signal levels are about 10 db hotter than typical "line" levels. Switching to low is a fine remedy. You can also unground pin 2 to reduce your level by 6 db. I only told you to ground pin 2 because you said you weren't getting enough level in your first post. Now you are saying you have too much level.
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Hello,
I've examined the Analog Rules site, and attempted to set bias and EQ on my machine according to their instructions, using their downloaded tones, but nothing happens.
For example, the site instructs you to turn the Bias screw to set the VU meters, but when I do this, the meters do not change their readings.
My machine has Bias Trap. screws on the back along with Monitor Adjust screws. There are also the Bias Cal screws on the front. Turning the Bias Cal screws appears to do nothing for the VU meters.
This machine was apparently last fully serviced in 1987 and not used since so I'd assume things like the heads, Azimuth, etc. were properly aligned.
Thank you.
I think we need to get a feel for what you're trying to accomplish here. It sounds like you have some experience with reel to reels so I'm guessing here that you have a particular tape that you wish to optimize your machine to. You may know this already but most home recorders don't have front panel pots for adjusting recording bias. They usually just have a switch that goes between 2 or 3 generalized bias levels. For most folks, they find the one that's best suited to available tapes and never touch it again. The pots for fine tuning the bias are located inside of these machines and it's usually taken to a tech if they wish to have them adjusted.
If you aren't positive that the playback head/amp isn't correctly aligned and adjusted, you have a good chance that you'll be changing a bias that's already correctly set, wrongly.
Even if the machine hasn't been used since it was serviced, it is very likely that it needs some work to get it operating correctly. We're talking about some pretty small differences in biasing a machine from one tape to another compared to the sonic effects of tape tension and other mechanical issues.
These machines are somewhere between an electronic device and a sports car. Much of what makes one machine sound better than another is how it moves the tape across the head. And just like a car, just because someone says that it was serviced before it was put in storage 23 years ago, you can't really expect it to run up to it's potential.
I strongly suggest that you leave the biasing the way you received the machine until all other adjustments and maintenance issues have been addressed. Only then will you be able to determine if something in the biasing is off and it needs to be adjusted.
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Hello,
Yes, I have some experience with reel to reels notably with the Teac A-3340S and Revox A77; the Teac was sort of a pro-sumer machine.
The Teac had a High & Low Bias switch so that was easily accomplished.
I usually use Maxell UD 30-180, which is what I'm attempting to bias the Otari to. I understand that this machine was previously used with Ampex 456. From all appearances, it looks like it hasn't been touched since its last service. I unscrewed all the other front panel adjustments to see what they looked like and all of them looked like they were adjusted since the screws matched in position.
I suppose at this point, I should simply return the Bias Cal screws to their original positions, which I had initially marked.
I must confess, I use a reel to reel solely to record my vinyl onto.
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If the machine was biased for 456 it should be fine with UD or almost any tape that would be considered high output. If you were to use a higher output tape like RMGI 900 or ATR Magnetics tape (both in current production) you wouldn't be taking advantage of the slightly wider dynamic range that those tapes offer but it would sound great anyway.
If your recording activities really take off and you need more tape, I'd suggest buying some from the two manufacturers who are currently producing reel to reel tape (the companies I mentioned above). Of those, RMGI 468, 911, or for longer/thinner tape LPR35 should work with the bias set like it is now. You can buy it and many tape supplies from US Recording Media.
http://usrecordingmedia-store.stores.yahoo.net/
BTW, There aren't that many of those 2 chassis Otari's around. How do the two sections connect? (if it's a single cable or more and how many pins are on each?)
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Hello ironbut,
Yes, I've managed to acquire a bit of that Maxell tape on 10.5 inch reels, some of it "virgin". I understand that the Maxell UD tapes are rather desirable for one reason or another. I did once have a horrifying experience with a reel of Ampex tape--it left residue everywhere it touched on the transport!
Anyways, the Otari is a 4 track with the main unit as one piece and the meters/amp in a separate chassis. You connect the two with four thick cords that have some really heavy-duty 10-pinned screw-in plugs: two for the Playback head and two for the recording/erase heads. The cords are permanently installed on the amp chassis.
There's also a thick three-plugged cord with some of those large rectangular 10-pinned plugs that connects Channels 1,3 and 2,4 together plus one plug that connects everything to the main unit.
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That sounds similar to the one I have. 4 channel 1/4" format. Those multi pin interconnects can cause connection issues.
I also like the Maxell tape. I have a bunch of old stuff on it and other than the leader splice losing it's adhesive, the tapes seem to have no issues.
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Hopefully with a bit of contact cleaner, they shouldn't cause any problems. They are some serious-looking plugs though.
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Back again!
Anyways, the machine was working fine when all of a sudden I turn it on and Channel 1 has no sound--this is a 4-track.
I checked all the leads from the head to the plugs, etc. and everything is fine. I even unplugged all the circuit boards, sprayed them with Deoxit and reinserted them to no avail.
Any suggestions?
Thank you.
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I don't know if you've cleaned the switches but it's always a good idea with these older machines. On some of the later models which have the 1/2 and 1/4 track heads the selector switch is a pretty common source of problems like this. Since yours is 4 track it won't have a switch like that but it should have one for each channel. While you're playing a tape, try switching that and any other switch that's in the signal path back and forth a few times(like your back panel high/low switch). I could just be a bunch of crud that the wiper is just moving around causing intermittent contact).
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The problem is that the source/tape switch seems to work, but there appears to be no signal to Channel 1.
When I switch it to Tape, there is the normal "hiss" of the channel being wired, but there's no signal at all.
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So, I'm assuming that this is when playing a tape that you've already established that channel #1 has in fact been recorded onto. If this is the case, does the VU show any signal present on that channel?
Just to double check things, get another tape and try recording onto channel #1 again.
You said below that you "checked all the leads fro the head to the plugs". Did this include a continuity test of each lead?
Also, is there some sort of switching for each of the 4 channels (not the source/tape switch). On most of these kinds of machines there's a way to control record or playback of each channel. Those would be the switches in question.