Saturday, July 2, 2011
Vintage Parts Excursion, Part 2: Capacitor leakage tester
Since my last episode with capacitor leakage it seemed necessary to cook up another piece of guitar amp specific test gear to complement the tube matcher I built recently, namely, a direct reading capacitor leakage meter and reforming device.
The original schematic was something I found In Alan Douglas' Classic Tube Testers and Test Equipment, but I've modified it a bit to suit local conditions, as it were.
It started out life as a Jackson model 645 vacuum tube voltmeter that had been lurking in the dark under my workbench. I didn't have a need for it but I couldn't bring myself to part with it-mostly because I like Jackson test equipment.
I'd been thinking about keeping it as is but it needed a special purpose 4.5 volt battery I did not have, so I proceeded to repurpose it. I built the power supply out of a Hammond organ power transformer and more terminal strips. They're great for prototyping things as they can be easily pop riveted in a convenient place.
At present it's been mocked up and I'm trolling through my resistor museum for combinations that meet the schematic value. And that's one good thing you can do with a lot of old carbon composition resistors is find ones that you can use.
In the meantime I ordered up a Russian military surplus analog 100 microamp meter that looks like reverse engineered Weston stuff-a fitting tribute to the men and women of Frelinghuysen Avenue.
I'll probably finish most of the wiring this weekend of the Glorious Fourth, and then station myself by the mailbox for the package from Estonia carrying my spiffy new Soviet microammeter.