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Author Topic: MX5050II - Issues with the recording meters  (Read 4469 times)

Offline rekloos

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MX5050II - Issues with the recording meters
« on: November 10, 2009, 01:10:44 PM »

 I had this machine for a bout 8 months but didn't get many miles out of it yet, just dumping loops etc. and i don't think it got much love before me.
The problem i have is that the recording meters are off by a lot, e.g. my right ch shows it's about 8-10 db louder when recording but when i play back
the material it sounds pretty equal in volume on both channels. I made the cables myself, twice actuallt because i've changed the configuration and i'm
positive they are wired correctly.
What could this be? I have the machine opened up and doing some cleaning and lubing so i figured while i'm at it try to fix the issue......

thx/
rek.

Offline Ki Choi

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Re: MX5050II - Issues with the recording meters
« Reply #1 on: November 10, 2009, 01:50:03 PM »
Try adjusting the VU meter needle position with power to the deck off to make sure they are both resting at the same far left position equally.

Sorry for the general information (it's bee a while since I played with an Otari...)
Then, if you have an external signal generator set its output to your operating level at 1Khz.  Measure the output with a multimeter to confirm the exact output level.
You would set the deck in input mode and check for the VU meter to read 0VU.  If not, you would need to adjust line output section.
As long as your operating level signal is reading 0VU, your VU meter is working properly in most cases.

The Otaris' have 1Khz and 10Khz tone generator built in.  I would engage the tone generator, disengage cal, and check both VU meters.  One of them is more than likely be reading properly.  You adjust the other one to get them to be equal.

I'll be helping a friend this Thursday in calibrating his Otari.  Hope to add more detailed information if you have not solved your problem still.
Ki Choi

Offline rekloos

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Re: MX5050II - Issues with the recording meters
« Reply #2 on: November 10, 2009, 04:21:43 PM »

 Awesome info Ki - i will do that tonite.
Feel free to post more info after ur done with ur friend's machine....
rek.

Offline rekloos

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Re: MX5050II - Issues with the recording meters
« Reply #3 on: November 15, 2009, 10:19:54 PM »
Try adjusting the VU meter needle position with power to the deck off to make sure they are both resting at the same far left position equally.

  -- done that



Sorry for the general information (it's bee a while since I played with an Otari...)
Then, if you have an external signal generator set its output to your operating level at 1Khz.  Measure the output with a multimeter to confirm the exact output level.
You would set the deck in input mode and check for the VU meter to read 0VU.  If not, you would need to adjust line output section.
As long as your operating level signal is reading 0VU, your VU meter is working properly in most cases.

--the only generator i have is coming from computer which goes thru my System 8 Console then to GL2 Mixer then to the tape machine.
  that's too many in the way, right? i shoul have a straight path from generator [computer interface] to the tape machine - i need to make cables for that.....



The Otaris' have 1Khz and 10Khz tone generator built in.  I would engage the tone generator, disengage cal, and check both VU meters.  One of them is more than likely be reading properly.  You adjust the other one to get them to be equal.

 -- also done that .


 well no luck so far. i also finished cleaning and lubing just about everything inside and out plus demag .
so what happens is if i record say at 0db on both channels on playback left channel comes out about 7-8 db quieter.
so if i was to select "SLR Output" then it'll play with left channel quieter while switching to manual and turning the
left channel up to compensate for the 7-8 dbs lost, it'll get louder but it also introduces more hiss. could this be head
related? and if so is it the recording or playback? i mean, when i read the VU meters while recording, that's before
the recording takes place, before the recording head - am i correct ??
the same thing happens when i'm monitoring while recording, if i select "Source" it shows me the VU meters being
equal and if i select "Tape" it shows me left channel lower in db......
rek.

Offline ironbut

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Re: MX5050II - Issues with the recording meters
« Reply #4 on: November 15, 2009, 11:35:47 PM »
So, let me make sure I have this right;

When you record with the input pot levels equal, the VU meters are equal when the playback selector switch is set to source, but when you switch to tape, the VU on the left channel swings to -7 or -8 dB compared to the right channel VU. Even though the VU is reading low on the left channel, the sound seems as equal as it does when the selector is on source?
In other words, the sound seems fine but the VU is off only when set to "Tape"?
If the sound levels comparisons between the left and right channel aren't the same on "Source" and "Tape" check to be sure that your playback head selector isn't set on 1/4 track instead of 1/2 track. Sometimes that switch gets gummed up so try switching it back and forth a few times.
If this doesn't help, if you have any tapes that are know recordings, check to see how those sound. It sounds like VU meter problem only but you need to confirm this with some sort of reference.
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Offline rekloos

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Re: MX5050II - Issues with the recording meters
« Reply #5 on: November 15, 2009, 11:43:51 PM »

  yes, i've checked the head selector and it was set right- also, it's been cleaned with deoxit.
and it's definitely an audio problem as well, the playback of the recorded material follows what the VU meters are showing - they're both lower in 1 channel.
rek.

Offline ironbut

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Re: MX5050II - Issues with the recording meters
« Reply #6 on: November 16, 2009, 02:38:27 AM »
So, it's an audio problem and the VU's are reading correctly?
Let me start by giving you an overview of the routing and how the VU's are patched into the network.

In short, there are 3 different things that the VU's will show.
1. When the input selector is set to source, it's only showing whatever is being input into the machine. The machine just has to be powered on for this (the tape doesn't have to be moving). Most machines have a built in mixer for the line and microphone inputs. Think of the input pot, mic pot and the VU (set to source) as part of this mixer. In fact, if you wanted to you could input a cd player into the line inputs and a mic into the mic input and a PA to the outputs and with the selector set to source, your machine would act as a mixer and you could adjust the relative levels of the two channels of the cd and the mic to suit your purpose. The VU would reflect the sum of the signals inputted into the mixer for the respective channel.
2. When the input selector is set to tape, it's showing the output of the playback amp which could be fed from the 1/4 track or 1/2 track playback head depending on where the head selector is set.
3. Record level, this is where you set the level that will be recorded. Record has to be engaged for this function although the tape can be stopped in "Pause" . This signal is routed from the record amp, through the input pot(s) and mixer.

The levels measured by the VU's will be different between #2 and #3. If you recorded a constant signal which reads 0 VU during recording, the level would be closer to -3 dB on playback because the VU's are measuring two different signals.

So, it's difficult to separate problems between recording and playback since to hear a problem in recording, you have to play it.
The main way to rule out a playback problem is to have a reference tape which was made on another machine of known integrity. You don't have to spend the money on a test tape if you know someone with a 1/2 track machine that is working pretty well. Just have them make a tape with equal signals on both channels and see if it works on your machine. If it does, it's either something in the record section or the tape you're using.

Also, just for fun, try playing back the tape you recorded with the head selector switch in the other position. As you said before, if this machine had seen a hard life, someone may have rewired the switch backwards.

As far as the record section goes, did it ever work correctly for you before?

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Offline rekloos

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Re: MX5050II - Issues with the recording meters
« Reply #7 on: November 16, 2009, 11:18:59 AM »

  I had this machine for maybe a year and it had this issue from the beginning so i've basicaly figured out the difference between the channels and
whenever i had to record something i would compensate by turning the right channel up - e.g., channel 1 would be around -1db and channel 2 would
be maxxed out in the red when in record mode, therefore on playback both channels would be really close to equal in loudness. like i've said before,
when you record and have the monitor selector to "Source", you get an equal loudness reading and when you select "Tape" you can see the difference
between channels so you just turn up the one that looks low in volume- makes sense??

I did playback the recorded material i have, from multiple tapes, at the other head selection [mine says "2Trk or 4Trk"] and the difference between the
two channels becomes even greater.

I don't know if i can get a recorded tape from anybody around here, not many 'tapeheads' i know of but i'll try.....
maybe it's time to invest in a MRL tape?
rek.

Offline ironbut

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Re: MX5050II - Issues with the recording meters
« Reply #8 on: November 16, 2009, 12:51:10 PM »
Ok,


I'm pretty sure that the info you gave in your last post points to the record section (all these details are key!). You stated that you have channel 2 pegged in the red. Normally, this would result in really bad distortion in that channel. If it isn't and the sound seems pretty good, the problem lies between the VU and the record head.
It could be something as simple as the bias switch or your record head adjustment.
Try toggling between the different bias settings while you're recording. (this is too easy not to at least try)

As far as your heads go, a new head's surface is even across it's width. When a head begins to wear, the tape (which is abrasive) wears a groove into this surface. On a well adjusted machine, this groove is pretty consistent (it's not deeper on one end or the other). That means that the tape is crossing the head with even tension across the width. If you take a look at the "Beginners Guide" it shows some pictures of different wear patterns. Once a head gets heavily grooved, it needs to be either resurfaced (relapped) or replaced.
Tape performance is in many ways, all about the tape/head interface. If you've ever heard a drop out, that's usually caused by a dust particle that gets between the head and tape. That tiny increase in distance is what makes the sound "drop" a few dB. So, if your tape isn't being fed through the groove that's worn into your head, one edge or the other is being held much higher above the head surface than any bit of dust could.
Another problem with worn heads, they make a nice "delta" for crap to accumulate. The left channel is the half of the head furthest from the machine. Because of this location, it's hard to see this edge of the head. Go back and clean the record head again and pay close attention to that outside half. Sometime it's hard to see this without laying the machine down or using a mirror.
Even if the heads are spic-n-span, and they aren't that worn, they could easily be out of adjustment.

One quick check is to start recording something, and while it's going, put a finger on the left reel to increase the back tension. If the levels increase, it could be a head adjustment or a tension adjustment. Normally you'd do both.
I suggest that you take your machine to someone with the proper equipment and test tapes and have this done.
They can also let you know if you need to have the heads relapped or replaced.
steve koto
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Offline rekloos

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Re: MX5050II - Issues with the recording meters
« Reply #9 on: November 16, 2009, 01:13:17 PM »

 The only thing bias related are the 2 knobs in the front labeled "Record Bias Ch1 - Ch2" and i know i kept them at equal settings - anything else related
to bias i should know about??

I'm gonna look into the head scenario tonight and see what i find out.
I know what you mean about taking it somewhere, i'd love to but where i'm at i don't have many choices in that department and one place i called to ask
about doing calibration would charge around $300, at least, which is more then i've paid for the machine itself....i don't know, it seems so much i could
probably buy another machine for that much that's already been calibrated.

I'll report later with results and i will check the guide as well.And thx for the great and fast responses you've been providing me with :))
rek.