Grounding Question

[VDOSC]

Hi all,
Can I connect the grounds of these two supplies, is this OK? I have popped the snubber cap on the negative rail (47u) and the regulator is kaput. I'm not sure if the cap was connected in reverse but, I replaced the regulator and cap and also disconnected the indicated ground and it's all good. Was it the cap or the grounding I'm not sure. I'm also not happy that this 338 burns with a reverse cap, if thats the case... (24V adjusted output give 35 after the pop and cap replacement... source is 40)

 

[rayma]

Not ok. You need TWO isolated secondaries, in order to series connect two power supplies.

 

[VDOSC]

You need TWO isolated secondaries, in order to series connect two power supplies.

Yes they are two separate secondary's off the same transformer hence the two bridges, no center tap. And actually the third on the bottom is the same transformer another 0-11.4V

 

[rayma]

Then if there is only one connection between the two supplies (at the outputs), they will work normally.

But you are not connecting the two "grounds" together. You are connecting the upper supply (-) to
the lower supply (+). Then that node becomes the circuit common "ground".

Similar requirement applies to the third supply.

 

[VDOSC]

Then if there is only one connection between the two supplies (at the outputs), they will work normally.

But you are not connecting the two "grounds" together. You are connecting the upper supply (-) to
the lower supply (+). Then that node becomes the circuit common "ground".

Thanks for the response, you have stated it more accurately, so it should be fine? Meaning no reason to blow the cap and regulator right?

 

[rayma]

No reason for a problem, but build and test each regulator circuit separately first.

Then add the common connection between the upper positive supply (-) and the lower negative supply (+) .

 

[VDOSC]

Thanks! Came out to be that I have soldered the cap wrong, took the 338 out on its way.... All good.

 

[rayma]

Good work.