[john-100]

Hi magnadave

what type of oscilloscope ?

in the past I've used a Textronix oscilloscope with the differential input option
it displays the difference between 2 probes , the earthed screens not being connected

battery operated oscilloscopes with an all insulated case are another safe option when you take care with the screen connections

John

[inertialabs]

John-100
It sounds like to implement the test you are describing you just wire up a 100w incandescent light bulb to the output of the motor control? The easiest place for this seems to be where the motor wires attach in the back of the cabinet will that work?

[inertialabs]

Those are the SCR's, I've replaced at least six or eight of them in our drive in the last ten years or so

Jon p
Can you elaborate on this a little more ? When you have replaced them what were the symptoms and how did you determine what components to replace ?

[magnadave]

John

I have an old BK Precision 1570A. I'll have to see if I can find the leads. Also one of the guys at work has a Fluke 123.

Dave

[john-100]

the BK 1570A will be OK
it lets you measure the difference between the A & B channels (with the ground clips removed)



this link shows how -

https://www.youtube.com/watch?v=VWodjUSkYVE

john

[john-100]

Hi inertialabs

since I've not worked on the bridge port drive my self
connect the lamp to the easiest , safe place you can
place the lamp in a position you can see the change in brightness as you adjust the control

John

[Jonp]

From my experience when you start blowing the fuse for the drive you have one or more scr's not working, I happen to have a Sencore scr tester so I'm not replacing all of them, usually only one or two are bad at a time. You need to test them as there are no visible signs of a bad one. Good luck. Jon P