QSF-V30S inconsistent speed

[Sean M]

We've been having an issue with our V30 that has been modified for B&W dev where the speed is inconsistent. I tested and replaced a faulty potentiometer but now the speed is maxed out and 80% of the speed knob doesn't change anything and only the last 20% will start to slow the motor. The problem is that now the lowest speed I can get is a 23sec dev time which is still way too fast. I tested the new potentiometer with a multimeter and confirmed that it is sending a full range of 0-20kohms to the speed control driver. I am getting a full 24v to the control driver.

[Dave S]

It's difficult to comment when I don't know how your system is configured, and which speed control driver is being used.
On a standard V30P machine there is a trim pot for each fixed speed setting, and also a trim pot for the main 20K variable speed knob pot.

Which pot did you replace? A trim pot or the main 20K pot?
How is your speed control system wired?

A wiring diagram would be helpful to understand your set up.

[davidlam]

Is it a V30P (variable speed) or.. or V30S Sean M wrote in your message SUBJECT ?

To my knowledge.. V30"S"   was Noritsu  "S"hanghai made model of film processor.

[Minilab service]

I think here is QSF-V30S, where installed QSF-V30P system software and changed processor drive circuit ( motor and speed control ) . Only film processor owner can know what they used there. First need to measure voltage on motor driver sped adjustment input. Need to know speed ajustment voltage is constant, or not. Then can know what causes instability - speed adjustment circuit, or motor driver.