Benchtesting a power supply

[Memphis007]

Hi everyone !

I'm trying to ensure that a power supply is delivering proper voltages and would like to know if I could do it the way I thought, schematics for it below :



I have an auto-transformer that I can adjust to the required 9.7V for the logic input power, i don't mind display input for now. On the schematics I find weird the joined 3j3-4 and 3j3-3 pins, why those pins are tied together ? Should I connect those as indicated ? Should I add an isolation transformer before/after the auto-transformer ?

Thanks for your answers.

[The Soulman]

Hi everyone !

I'm trying to ensure that a power supply is delivering proper voltages and would like to know if I could do it the way I thought, schematics for it below :

(Attachment Link)

I have an auto-transformer that I can adjust to the required 9.7V for the logic input power, i don't mind display input for now. On the schematics I find weird the joined 3j3-4 and 3j3-3 pins, why those pins are tied together ? Should I connect those as indicated ? Should I add an isolation transformer before/after the auto-transformer ?

Thanks for your answers.

I'll answer backwards:

Should I add an isolation transformer before/after the auto-transformer ? YES!

On the schematics I find weird the joined 3j3-4 and 3j3-3 pins, why those pins are tied together ?
The original transformer has two 9,7V secondary windings in series with the center tap connection connected to ground.
For testing you'd need to replicate that, or simply use the original transformer?

[The Soulman]

From what type of device is this? a (french?) vcr or something?

[Memphis007]

Ok, seems much clearer now, I should have looked closer at the transformer schematics... it makes perfect sense.

It's from a Williams pinball machine. That's why I wanted to avoid removing the original transformer from the cabinet.