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ewildgoose 29th October 2004 12:46 PM

Zappulse PSU wiring problem
Hi, can anyone familiar with the LC Audio predator PSU tell me what I might have done wrong here.

I have wired my predator PSU up as shown in the photo below, since it's a dual mono supply I thought I was doing the right thing by shorting the inputs across as shown...

However, when I powered the thing on I promptly blew all the fuses, and on testing with a meter I can see that even with all these input power wires completely disconnected I have a short from any of the power input connectors to earth... There is also a short between any two power inputs

Does this suggest that I have fried something? Any ideas on what and why?


Ed W

chrisb03 29th October 2004 01:00 PM

I think you may have a problem. Do you have only one secondary on your transformer? You should have two separate or one with center tap.

Here's a link with the predator circuit.

Following the circuit may point to what is happening.

ewildgoose 29th October 2004 01:05 PM

I have two secondaries, but also two powersupplies (one per channel).

I had (naively?) assumed that the way the PS was wired up here would have been ok? (The predator PS is setup so that you have up to two power inputs to run each rail seperately)

What have I likely broken...?

chrisb03 29th October 2004 01:07 PM

When you say two secondaries, do you mean on each transformer or in total? I can only see one secondary on the transformer shown.

This is what it should look like.

wytco0 29th October 2004 01:38 PM

I also have a predator power supply and I am very disappointed that LC have not produced any documentation to go with it.

For experts this is not a problem but for people like me it is, the module does not even have any markings showing where the DC is and the transformer connections have no markings either.

I am amazed that they have produced this board without any documentation.

I wanted to use mine with a centre tap transformer but I have not been able to work out if this is possible.

I have told LC audio all of the above :mad:

ewildgoose 29th October 2004 02:12 PM

I have only two secondaries on the one transformer (total, ie no second transformer). But I have two predator PSU boards.

I can't see any reason why I need two secondaries for each predator though? My wiring should be correct I feel?

chrisb03 29th October 2004 09:17 PM

From what I have understood, this is incorrect. Wire both secondaries to one predator in the way shown in the picture and circuit

Then you will have to either get another transformer or just parralell wire the other predator of the other. That is, wire pin 1 to pin 1 etc.

Best option in my opinion is to buy another transformer, one for each predator. Mono blocks.

ewildgoose 30th October 2004 08:01 AM

Hi Thanks for your thoughts. Can you expand on why you think my wiring is incorrect?

I am basically just paralleling one secondary into each powersupply. I could put two secondaries into one powersupply and then parallel across to the other I guess? Don't see that it would make much difference mind?

As for second transformers. These are 1Kva jobs, and I could never fit two of them into any practical case (or lift it), and I don't even know where I could get two reasonable sized 500Va ones from. So I think I am stuck with this one.

Basically, I'm not sure how I have blown up the board with this wiring...?

Lars Clausen 30th October 2004 12:41 PM

wytco0: We chose to publish our documentation online, not on paper.

In this case our online documentation can be found here:

This way people can browse our docs before purchasing anything, and even find it years after they may have thrown out the papers that came with the unit.

ewildgoose: You are trying to get one transformer winding to produce both negative and positive voltage simultanously. It can be done, but will never be a very good solution. And definitely can not be done by simply parallelling the two bridges for positive and negative supply directly like shown on your picture.
I think this is an example of how things can go wrong when the user hooks the module up in a completely other way than suggested in the instructions provided by us. (above). I suggest you get a transformer for each predator power supply, and then hook it up as shown in one of the two different examples on the above page.

Then you will have no difficulties at all getting it to work correctly.

Nice antique chair btw :)

All the best from


ewildgoose 30th October 2004 02:18 PM

Hi Lars, thanks for responding (especially as I hear that you are out of town at the moment?!)

OK, I don't quite understand (yet), but I think I am starting to think that the second bridge rectifier is the issue...?

I definitely can't fit two transformers into this box (it's an 80mm high case of the max width/depth possible from the supplier. 500Va and above transformers aren't going to fit if I have two of them). Right now I have a 1000Va transformer in there.

So is there another way that I could wire this using only two secondaries, but with two predator PSU's? How about the suggestion above, to use both secondaries to one supply and then parallel each secondary to the other supply...?

Finally, I guess I have destroyed some components on the PS board? There is an open circuit to earth on both boards. I guess this means that I have at least blown the rectifiers? Am I likely to have also blown the ferrite beads and small caps? Nothing looks obviously damaged, ie there are no external clues like burned components.

Can you provide some advice on RS or Farnell codes for these items so that I can replace them (or would you be willing to repair the boards?)

Thanks Lars

Ed W

P.S. I see what you mean about the "antique" chair... Hadn't noticed it in the picture before! It's an old rocking chair which folds up - and it is rather nice actually!

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