NOTE 7/2020: I have discovered a limit on how fast the saddle can be moved without losing Z counts.  I assumed the limit would be above my maximum hand crank speed, but it turns out that you can lose counts even with moderately fast cranking – somewhere around 2″/sec saddle movement. For now, I manage by watching my handwheel speed, but it appears a faster uC than the MSP430 is needed. I will update when I have a solution.

12/7/22 – I just stumbled on this ESP32 Touch DRO setup on a site called Stockholmviews.com. This would most likely solve the above speed limitation since the ESP32 is much faster than the MSP430. I have not tried it yet: https://www.stockholmviews.com/wp/touchdro-diy-esp32-interface/?fbclid=IwAR0r8TOkRoQZHnrKf1z1ZNt1GjiT2w0daOuAEruxRSRDF2HHSnfO1FZsTZI

This is an outstanding machine DRO for hobbyists, not just an outstanding DIY project, but a super DRO even compared to high-end pro machines. The beauty of TouchDRO is that it uses a (cheap) Android tablet for the display and control (I used a 1st-generation Nexus tablet – $50 on eBay) while the scales connect to a small (user-built) box that wirelessly sends data to the tablet via Bluetooth. The extra cute thing about this particular DRO installation is that all that parts are very small and don’t interfere with any travel distances or setups on this already smallish machine.

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This is bender specifically made to put a very tight radius bend in 5/32″ brass rod for banjo hooks. The original design was modified from this:  http://www.micromark.com/universal-bender,8229.html  but required a few revisions to get the desired result. Finally, when I was able to force the rod into a tight radius bend, some would crack. I learned that they needed to be heated with a torch before bending, but don’t have to be bent while hot.

The key difference between this and the little universal bender (besides less “slop” and tighter-tolerance fittings) is the movable round die is a “cam” that can be pivoted (with a 3/4″ wrench) and forced tightly against the stationary die while the bend is being made.

This was also my first exercise with hardening O1 tool steel. There are tons of guides on line covering this topic so I won’t go into detail here. Having the working surfaces hardened may not be necessary for bending brass but I wanted to play with O1 steel and this was pretty forgiving applications for a first try. It went quite well.

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This is a tube harmonica amp I built for my wife. It’s loosely modeled after an old Fender “Champ”. The circuit is a single-ended 6L6 design from Lone Wolf Blues: Lone Wolf Blues 6L6SE

The cabinetry and hardware became sort of an art project:

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I found two heavily trashed Ainsworth antique balance scales at the flea market. $40 later, they followed me home. Between the two carcasses, I was able to get parts to assemble one complete unit. Continue reading →

This is a home build of a two-channel tube-based studio preamplifer / direct box. The project web site is here:

Gyraf Audio G9

There are several recommendations/changes I have for future G9 builds, but it will take some time to get it all posted. Here’s an interior shot of my completed preamp.

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This home-made surface mount device (SMD) tweezers/probe is made from scrap PCB material and plugs into a DVM or capacitance/inductance meter for easy measurement of tiny SMD components Continue reading →