Replacing Capacitors on Speakercraft MZC

I have two Speakercraft MZC-66s. Last December, both started to make an incredible buzz and click sounds whenever the power was on — even if the zone was off.

I ended up re-capping them and now they are nice and quiet again!

Each zone has its own dedicated amp – kinda dumb. Why not have a bunch of amps that can be assigned to various zones on a rotational basis so each amp runs for the same # of hours? Oh well. Another poor design decision is putting a bunch of electrolytic capacitors right under the heat sink. Think they might dry out quicker there?

Warning: Obviously, doing this will void any warranty you have. This process worked great for me, but yours may get destroyed in the process. Your mileage may vary, you have been warned, blah, blah blah.

Obviously you should unplug and have the power off!

On the back of the MZC you need to take out two screws holding in the individual amp. Remove the two on either side ofthe EZ-PAD green connector.

Then take off the cover of the amp.


In this picture, you can see I’ve removed one of the zones. You’ll need to take off a couple of cables and two screws that are at the bottom of the amp. This is a MZC-66 – so there are 6 amps. Once you remove the cables and screws, you should be able to gently lift out the amplifier.


In the above picture, you can see one of the amps removed from the MZC. The big aluminum block with fins is the heat sink for the amp chip which is wedged under it. There are two circuit board remnants used as spacers on either side. Remove the screws on the bottom of the board that hold on the heat sink and spacers and set them aside.

Here is the amp without the big heat sink. You can see the amp chip with its own heat transfer plate on it and some left over heat transfer paste. I’ve labelled the capacitors that I replaced. Since I was going to do this, I replaced caps C1-C5 on all my amps. No point doing just one and then having to replace the others later. Sooner or later they will dry out. I did replace a few of the smaller caps near the connector but they didn’t seem to be an issue.
These are the capacitor specifications that I could read off them. Yours might be different, although this was true for both MZC-66s I have.

C1 & C2: 470uF 35V ELZA350ELL471MJ16S
C3: 47uF 63V UVZ1J470MED
C4 & C5: 47uF 35V ESH476M035AE3AA

I bought replacements from Mouser, links above.

I soldered off the caps, see above and installed the new ones.

Installation is the reverse of removal. I suggest you put on some new thermal paste on the chip before reseating the heat sink.

I hope this tutorial is helpful and happy rock’n out.