Diode isolator for multiple PSUs

[ExitThirteen]

Heya folks! I recently acquired a project amp to work on, and it has (5) of the Mega Watt 400-12 (36A) supplies in it. I'm pretty sure need to build a diode isolator circuit so I can run the supplies together without an issue.

Do I just use a 40A diode on each positive wire coming off the supply to the +12V rail on the amp? Or is there something else I need to do. The power supplies are not happy at the moment... pretty sure they need to be isolated so the regulators in each supply don't have to fight each other.

Comments, suggestions, rutabagas? Thanks in advance.


~Cheers~

 

[nomadradio]

The output of a Megawatt switchmode supply IS a diode.

More or less. You only need to add diodes with power supplies using series-pass transistors to feed the output terminals. The big, heavy supplies with a large 60-Hz transformer and a row or two of power transistors need the diode in case one of them shuts down. When it does, the voltage from the other power supplies feeds into the one that has shut down. Puts a reverse-polarity situation onto the regulator transistors. Reverse polarity is never healthy for transistor circuits.

A switchmode supply typically does not have this hazard built into it and you can skip the diodes.

73

 

[ExitThirteen]

Well, I do know that the supplies are not happy running in parallel... they make a hissing sound and it makes the amp do some weird things, too. Any suggestions on what I can do to remedy that problem?


~Cheers~

 

[2315 Robert]

Well first of all those are more robust and lest susceptible to damage(than the 50 ampers) , They are much quieter. So equal length wire is advised, All supplies set at same voltage. The diode for protection your choice. 40 is over but that makes sense. The 50's are like talkback transistors. No way to know if demand on one is greater without a measurement.

 

[nomadradio]

Hissing sound?

Only when you're keyed up?

73

 

[2315 Robert]

NR totally correct I have 3 of the 50 amps tied together. They will not deliver amps that take them out sequence.

 

[ExitThirteen]

No, it hisses all the time. If i disconnect all the positive wires from the +12V rail on the amp, and then I touch any two positives together out of the five (the grounds are all tied together on the -12V rail), making them parallel, they hiss... it doesn't sound good. They don't play well if any of them are hooked in parallel.


~Cheers~

 

[2315 Robert]

LDMOS 13?

 

[ExitThirteen]

The amp is a 2 x 8 2879 box.

It runs (5) of the Mega Watt 36A switching supplies in parallel. The supplies don't like being ran in parallel, hence the reason why I'm asking about diode isolation.


~Cheers~

 

[2315 Robert]

copy not series

 

[2315 Robert]

I think the supplies are well made. But switching supplies are like our next generation of phone pokers. A regulated supply will be stable and dependable(heavy), The switchers fight and power(amp) down to protect themselves.

 

[Shadetree Mechanic]

Make sure the voltage adjustment are set to the same voltage? Try some diodes to see what happens. It certainly won't hurt.

 

[ExitThirteen]

Yeah, they were all set to within .03 of a volt of each other.


~Cheers~

 

[Tallman]

https://www.worldwidedx.com/threads...r-supply-comparison.182976/page-2#post-517318
Add one more diode for three power supplies.
This is how John Marles said to parallel the supplies. I have two of them done this way and have run them for over six years .

Amazon product ASIN B0081SB4WQ

 

[Tallman]

premade unit for three power supplies:
Amazon product ASIN B0081SB4WQ