Not an amp - but need help here MixWizard 16:2

[ChancesR]

This Allen Heath mixer came in - smoking through one of the inputs. Found a blown electrolytic (35V, 2200uF) on the rear panel board. It appears another has been here before me, as this is the second attempt at a repair for this. I have a suspicion that the 2 caps here have been reversed in some way. Currently they are in series. This isn't a 'printed' circuit board. I'm unable to find any lead to a schematic to check my theory, and reverse-engineering is really not an option here. ha

If anyone has information on this, I appreciate it already.

Thanks so much-
ChancesR

[Mark Black]

With the value you mention those must be power supply filter caps. A typical layout would have them right next to each other with positive of one cap connected to negative of the other. That connection will be power supply common (or ground if you will). I suppose you could say the caps are connected in series but I've never thought about it that way.

To see if the caps are in backwards find the bridge rectifier (should be close by) and check for continuity between the positive output pin and the positive side of the cap which has its negative end connected to common. If there are 4 discrete diodes making up the bridge rectifier find the two that have their cathodes tied together and that will be the positive output.

The other cap should have its negative tied to the negative pin of the bridge rectifier (or to the point where two diodes have their anodes tied if discrete).

Good luck!

[ChancesR]

Hi Mark,
Sorry for the huge delay in responding to this. I was able to use your guidance to a very happy ending! I *did* find some stensiling on the board for the supply rails.....you were right about that. This was the 16/17V rails. I replaced both caps, in the proper position...and no explosions. THANKS so much for your help.

Regards,
ChancesR

[Mark Black]

That's great!

Always nice to hear of a happy ending...