BIAS question

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fgonza2

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While trying to BIAS the MS16, i am running into the following issue:

-Tape is SM911 RMGI
-I put a 10khz -10VU signal (also tried at 0 VU)

As i start moving the BIAS trimmer, the level comes up up, it reaches the end of the VU meter and never reaches a peak. THe peak is the end of the BIAS potentiometer it never comes down again. I see this in several channels, have not tried the 16 of them. Does this sound familiar to anyone ?
 
Turn down the level of your test tone.....the only thing that is relevant is the rise/drop point and the amount of dB you are going to use for your bias setting...not the actual level of the test signal.
 
maybe i wasnt clear enough. even with a low level i dont see a peak ever. I even turn the rec level down to give more range on the VU meter, but the trimer gets to its max and the level goes up and never peaks, no overbias range.
 
Oh...I see.
The actual pot is reaching its limit.
I didn't catch that. I thought it was just your VU meter.

I've run into that a couple of times. I think I just went to the end, and then guesstimated from there as best as I could.
 
This is definitely not normal. I wonder what the problem may be. Either all the cards were modified, or the bias is not enough for some reason, maybe a power supply issue ?
 
Weird prob if you can't find the peak even after bringing the rec level almost all the way down, am I reading that right? I have occasionally had to bring the rec level down on certain channels to get more VU range while biasing for +9 on my machines, but never a prob like yours where I could never get the peak in VU range after pulling the trimmer down a bit.

I don't know the MS16 so bear with me. Can you probe around and see if the correct bias current is getting into the problem channels? Can you also confirm that your rec levels are indeed being attenuated and the VU isn't showing incorrect level? Is it possible to swap cards between channels in the MS16 to see if the problem follows rec or bias cards?

Have you calibrated the VUs and the levels at the input and output to make sure what's going in is what's coming out? Finally, can you get the bias for the problem channels roughed in by ear? Bright and crystalline sound = not enough overbias, too dark and cloudy HF's = too much...
 
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never seen this b4, bias makes a great stuff, hope you will find a solution, better write tot heir support :)
 
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