VU build from a old tape deck.

Omen

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Feb 21, 2015
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Sydney
Hi! I pulled this nice set of VU meters from a old nakamichi tape deck. The deck powered up but I think the belt was shot. Any way I was going to build another set of VU's for a mate. I was stoked that I only had to unscrew two screws and the whole VU module popped out. I hooked up some power and the lamps fired up! Good start! I tried to get some 1kh test tone signal in from my 02R in to it. I can get the needle to move a little on each meter but not much. So I know which cable is left and right and I assume that the only cable left would be the - cable. Another funny thing happening is when I turn up the gain on the test tone the needle goes down more not up!
Maybe you can see from this photo wot I'm doing wrong. I'm using my JLM VU meter kit I built as a reference but it's not happening. Cheers
 

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pcrecord

Quality recording seeker !
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Feb 21, 2013
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Quebec, Canada
A needle going down seems like a gain reduction behaviour to me ;).
The reactions you get can be very different depending on the polarity and how much electricity the unit is suppose to receive to react correctly.
The best thing is to analyse the power that goes to it in it's original use and/or start from the schematics.

I guess the best one to guide you on this is @Boswell
 

Boswell

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Apr 19, 2006
Location
UK
Another funny thing happening is when I turn up the gain on the test tone the needle goes down more not up!
Maybe you can see from this photo wot I'm doing wrong. I'm using my JLM VU meter kit I built as a reference but it's not happening. Cheers
What's the meter reading with no signal input? Does the needle "go down more" in proportion to the signal level, or does it only start to go down at a certain amplitude of input?
 

Omen

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Feb 21, 2015
Location
Sydney
Thank you Boswell and Pcrecord for taking the time to help.

I put a multi meter over the power pins on the tape deck that the clip came off and it read 11.94 dcvolts. So 12volts. I'm using a 12volt power supply.

The meter is reading at below -40 with no signal and starts going down when I turn the test tone up from -20db and more. So it does only start to go down at a certain amplitude of input.
 

Boswell

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Apr 19, 2006
Location
UK
I'm sorry, but I don't fully understand what you are describing. Are you saying the meter reading stays at or below -40 with all signal levels up to -20dBu and then (somehow) goes lower than that for signals greater than -20dBu? Are there any input signal levels for which the meter goes above -40?
 
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