December 13, 2015 at 4:10 pm #15340Ted FletcherKeymaster
I have just had a request for alignment procedure for the P38EX.
I have included it here as it might be useful…. and a useful tip about measurement!
To align the VU meters on the P38EX…..
This is the simplified method assuming that you do not have laboratory test equipment…. it uses just a simple AC digital voltmeter.
Put a sine wave tone of about -5dBu 300Hz into both inputs. (NOTE, AC meters are generally not accurate above 400Hz)
Set the input gain control to No6.
All buttons should be OUT. set Stereo Width to MONO, set balance to CENTRE. Set mix to100%.
Measure outputs with AC multi-meter and adjust Output Gain control until outputs are 0.775VAC (this is not too critical, they will vary a little). This should correspond to a setting of about ‘0’ on the output gain control…if not, adjust the input gain to suit.
Now using a small standard screwdriver with a flat blade (about 1.5mm wide), adjust the meter presets to set the VU meters to ‘0’. The meter presets are accessible through small holes behind the meters. If in doubt, remove the top cover (10 self-tap screws) and the meter presets will be obvious.
To set the compression zero on the RH meter, remove all signals, remove top cover, press meter switch and adjust the GR preset in the middle of the PC board. This setting was done during manufacture and it is very unlikely that it needs to be touched.
NOTE, the VU meters are set up to read ‘0’ at zero dBU output. I do not recommend setting the VUs to +4dBu as this can lead to over-driving the output stage.
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