If you remember, the previous version of the Cheapzuma looked like:
The four OEM Ford speakers were each rated at 25W / 4 ohms, and becuase I was using a single T-Amp board to drive them, I had to wire them in series, effectively making each pair an 8-ohm speaker. The T-Amp can drive 15W into 4 ohms, but only 10W into 8 ohms. Since I wasn't really tremendously happy with the output of the first Cheapzuma (its primary design goal was cheap, not super-loud), I wanted to see about addressing that problem while I was already tearing the thing down.
Here's the front-on view of the finished product. I decided to go with a tall, narrow box, and arrange the speakers vertically, rather than the original 'X' layout. This makes for a more compact unit to drag to tournaments. The case on this rebuild is actually some 1/2" birch plywood I had leftover from a cabinet project I'd recently finished, and as is becoming my custom, the finish is Plasti-Dip.
Because I wanted to add some ooomph to the build, and having several T-Amp boards laying around, I decided to use two amp boards, and have each board drive a pair of the speakers. This allows each board to drive the speakers at 4 ohms. Instead of 2 channels at 10W per channel, I should end up with 4 channels at 15W per channel.
To accomplish this, I first decided I'd want an upgraded battery, so instead of the 5Ah SLA of the original plan, I picked up a 7Ah alarm batttery. From the power switch, I simply ran two sets of leads (one to each board) for power, and shorted the two red leads on each amp board to make them permanently "on".
Rather than try to deal with two volume controls, I also shorted the volume control leads on the amp boards, rigging them for full-volume output. On the connector, there are 2 red and 5 white wires. The red wires, as previously mentioned, are for the power switch. If you number the white wires 1 thru 5 (it doesn't matter which end you start from, as long as you're only counting the white wires), simply connect wire 1 to wire 5 and wire 2 to wire 4. Wire 3 is there to connect the ground plane to the factory potentiometer, and can be left alone. I used the same type of pot from my Podzuma rebuild in this one (50 Kohm, audio taper, dual gang), but wired it directly to the input jack on the top panel. From the pot, I simply ran two leads per channel to the amp board headphone inputs (making sure everything is also tied to the ground plane).
A quick bench test actually pointed out that I had a bad left channel in one of my recycled original Sonic Impact boards, but swapping in a Dayton DTA-2 fixed the issue, and I was able to verify that all of the speakers were being driven properly.
Instead of the Penn-Elcom steel dishes, I used the plastic tops of some Radio Shack project boxes I had. As with the Podzuma, I routed a slight relief to accomodate the lip of each cover, but I liked the way they looked sitting a bit proud of the case, so I didn't stress over really recessing them.
The bottom cover is the battery access, the tall, narrow cover is for access to the electronics, and the top cover is simply there to mount the controls. I left out the 12V-out jack (never really having used that feature on the Podzuma), but otherwise, the battery-charging circuit is the same as the original.
Finally, because I'd never encountered a situation where I'd used the original Cheapzuma without using the cheap Wal-Mart luggage dolly to roll it around, I decided to pick up some 3/4" pipe-mounting clamps and attach the new 'zuma permanently to the dolly. I used "Wall Dog" screws because they have a very large, aggressive thread which seemed like it would stand up to the normal jostling of transit better than standard wood screws.
As with the Podzuma rebuild, I'm insanely pleased with how this came out. The difference in output from the previous Cheapzuma is noticeable, although I still think the Podzuma (benefitting from being designed by a professional) has better performance, particularly on the low end.
Since it's loud and (relatively) cheap, I might have to start calling this one the Janicezuma (after Chandler's ex-girlfriend from the show Friends).
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