Model 140 Vu Meters

[Boogies1018]

I’m restoring a model 140 amp and the service manual vu meter adjustment has me baffled. I messed with it for 2 hours trying to figure it out. Am I making it way too hard?

 

[ChrisMarantz]

There are 4 steps to the adjustment process - what about it are you finding baffling? - Chris

 

[Boogies1018]

Once I have the DVM in the speaker terminal do I play like a 1hz tone then turn the gain up on that channel to 9v and adjust RX07 to 0VU? I've probably read to many different ways to do this combined them in my head and made it way too hard.

 

[ChrisMarantz]

Once I have the DVM in the speaker terminal do I play like a 1hz tone then turn the gain up on that channel to 9v and adjust RX07 to 0VU? I've probably read to many different ways to do this combined them in my head and made it way too hard.

Yes - except I would would a 10Hz frequency - then you increase the output to 16.0 volts RMS and set RX03 - Chris

 

[Boogies1018]

I guess my last question is how loud or how many volts should my input signal be? I'm playing the signal from my laptop and I can measure the voltage coming out of the RCA cables.

 

[ChrisMarantz]

Lets take the Right-Channel as an example - You set to gain control for the Right-Channel to maximum - then you raise the level of the input signal until you have the required 9.0 Volts on the output - After setting RX07 to 0VU - You increase the signal until you have the required 16.0 volts on the output - then you set RX03.

Repeat for the Left-Channel - Chris

 

[Boogies1018]

Ahhhhh there was my problem. I didn't set the gain to max then add the signal to 9.0 volts. I was doing it backwards which was making no sense at all to me. Thank you sooo much for that!!