DIYstompboxes.com

If the rear side is easy to access, I'll sand it all down. Actually, I find an Orbital sander can make a neat scrubbed finish to alumin(complete your own spelling).
Small holes I deburr With a countersink (handy in an electric screwdriver). Larger I use the step drill. Larger still, I use a knife or chisel.
Drilling through to a sacrificial backing can help, but the soft metal will still jump up around the bit and let a burr form. Also, the material you want to use up for the backing can be soft enough for a burr to form into it (drill a lot of holes and the metal can be semi-riveted to the backing by the burrs).
I've never owned or used a proper de-burring tool so I wouldn't know what might be a good one.

Yes it's a phaser/tremolo controlled by a single LFO

I use one of these-- chucked up in a nut-driver handle... I follow the drilling, top and bottom with a couple twists, and it blows the burrs off the metal.

https://www.harborfreight.com/12-in-six-flute-countersink-61552.html

Won't work if the hole is 1/2" or larger however!

MC

Welcome!

Thank you, again, I can't say whether the Hfe value from my component tester is necessarily accurate, and it's not clear that the 79 on the packet is Steve's Hfe measurement, but he did put in resistor values suggesting that this would be a good transistor for the traditional circuit. The transistor was sitting in my garage for a year or two though, so maybe that, or the soldering, could have affected performance?

I figured that since i was using a PCB and a pre-tested transistor, this would be a cakewalk! I had no idea that the rangemaster could be so high maintenance! OK, will pull the tranny out and try it on the breadboard.

79 is the Hfe and L = Leakage.

Did you socket the transistor, or apply heat directly to the leads? If the latter, did you heat sink the transistor? It's not all that hard to damage a transistor when soldering it into a circuit.