In this video we will calibrate the meter of an Urei LA4A – or the PCB Grinder Hand of Light Unit for accurate tracking.

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Gain Reduction meter adjustment (MTR0 on HOL – Hand OF Light)

  • Startup Unit (it is better to wait a few minutes afster startup)
  • Put meter in GR 
  • With no signal applied it should read 0 VU
  • If not Adjust MTR0 potmeter

Tracking Meter Adjustment (MTRT on HOL)

  • Apply a sinewave 1000 Hz between 0.1 and 1.4 V – I used 1V
  • Put meter in OUTPUT
  • Adjust output until meter reads 0 Vu
  • Adjust Treshold until meter reads -5Vu
  • Set meter in gain reduction
  • This should read also -5 VU
  • Adjust MTRT until meter reads -5 VU

 

Video Transcription

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today we’re gonna calibrate this hand of light unit by PCB grinder it’s a LA4A

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copy it’s a fairly easy build took me
about 40 minutes so the only thing you

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have to do is to adjust some potentiometers inside the unit and we’re ready

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to go so let’s turn it down and the only
thing you need to adjust this is a

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little screwdriver let’s open up the
units be careful with the power supply

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and stuff so you don’t get any electric
shocks but normally if you just stay out

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of this zone over here it will be all be
good. If we turn on the unit and we are

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in gain reduction mode it should say
zero and it isn’t so adjust it until it

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is zero more or less it is. Now we will add
one kilohertz sine wave with voltage of

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1V so let’s add it you can do it with
your audio interface as well. If it’s between

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100 millivolts and 1.4 volts it
will be ok. Just there is some singal. We

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will turn the unit in output mode we
will add output so its signal will be on

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zero volts. Here we are and now we will
subtract 5V from the meter

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so with the threshold we’ll go, my
ratio is on 8:1, until minus five

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If we go to gain reduction mode
normally it should say also minus five

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here we go. But it’s minus one so we will
adjust meter tracking, that’s this one

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Here we are. Your unit is ready and
set

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One thing I will advise
you guys it’s not to case two of them in

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one unit I think I will recase mine
I made this units I think a few years

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ago it’s one of my first builds I did so
that’s why it’s a little bit more

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messy as my newer bills but we all have
to learn about it.

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Thank you for watching

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and see you soon
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