Author: lens42

A Better Mouse (and Rat) Trap…Seriously

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Setting rodent traps in awkward areas like attics and crawl spaces is hard enough, but checking traps in those locations every few days gets tiring, to the point where maybe you skip a few days, then forget where the traps are. Then you get, “What’s that smell?”.

I want to be able to check traps frequently, but without crawling around, preferably from a comfortable chair while using my my smartphone. There are products on the market that feature remote monitoring, but they are extraordinarily expensive, and often only available through professional exterminators. Victor also sells a WiFi enabled rat zapper, but my experience with it was not good. At $60, the price is not out of line for a WiFi enabled device, but it didn’t actually catch any rats for me.

I’ve always had decent results with basic snap traps with the yellow paddle, as shown below. I find these easier to set than snap traps with the tiny metal catch. The perfect solution for remote monitoring would be this kind of trap, but with a wireless status flag. In today’s world of IOT devices, I’m a bit surprised that this isn’t already sold at Home Depot, but AFAICT, it’s not.

Low tech, but effective, snap trap
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A Dynaco ST35 Tube Amp Built In The Style Of Classic McIntosh

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TLDR: 17 Watt per channel Dynaco ST35 built as a “mini”
MC275 (i.e. MC217)

I’m a fan of old McIntosh HiFi equipment, especially their tube power amplifiers. They have a very unique design both electronically and also physically. For those unfamiliar, below is one of their flagship amps of the 1960s, an MC275, which outputs 75 Watts per channel…..and weighs close to 70 pounds!

McIntosh MC275 Power Amp – A tube stereo classic

I’ve had, for several years, a partial collection of parts (transformers, tubes, etc) to build a copy of a much more modest stereo amp called the Dynaco ST35. Dynaco was a lower cost competitor of McIntosh in those days but was still considered a good quality path to HiFi for many budget conscious college students (like me). As you can see below, the Dynaco unit, true to its budget genealogy, is a pretty plain box.

Dynaco ST35 tube stereo power amplifier output 17.5 Watts per channel

I wanted to make use of my tube amp parts, but in a way that “looked cooler”. I decided to build a “Mini-me” of a McIntosh MC275 with the innards of a Dynaco ST35. The key to this would be the metal work. Two tricky aspects in particular were the McIntosh slanted front panel and the transformer covers.

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“Arty” LED Patio Light

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We have a fairly large patio that was lit by one crummy three-bulb can type fixture. In the evenings the light was horrible – too bright under the fixture and dark everywhere else. The ceiling is also fairly low.

I had an idea of using several LED MR16 bulbs and copper tubing that would be like branches of a tree. This “natural” look also had the convenient advantage of requiring no precise bends 🙂

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Minimus 7 Speakers -Terminal Post and Crossover Upgrade

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I dug out a pair of the Radio Shack classic mini speakers, Minimus 7s, that I hadn’t used for years. They became part of a major HiFi downsize because, I was forced to admit that our previous speakers were too damn big for the room. One major problem cropped up however. The spring loaded wire clips lost all their “grab”, so the wires wouldn’t stay in. I don’t know if this is a common Minimus 7 problem, but it was pretty bad on these.

I decided to replace the spring clips with binding posts which meant pulling the speakers apart. In the process of looking up how to open the cases up, I stumbled onto articles about upgrading the crossovers, and figured, “Why not?”

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uTracer Vacuum Tube Curve Tracer Build

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This post is mostly a shout out to Ronald Dekker, the inventor and seller of a very neat tube tester kit called the uTracer. I did quite a bit of web searching before buying this kit in 2014. It was at that time, and still appears to be, the best device of its kind, especially when you compare to the (high) prices of old tube testers or (you better be sitting down) a Tektronix 570 curve tracer.

I had a large stash of tubes I wanted to sell on eBay. I found that I got much better prices for tested tubes, and in the case of audio power tubes, EVEN BETTER prices if I matched characteristic curves. The uTracer device seems to be, far and away, the best most cost effective device to measure detailed tube data. Buyer’s were very happy when I shipped a curve-trace plot with each tube.

The uTracer is an extremely well thought out design. It is a perfect blend of old and new in that it measured tubes but interfaces to a PC, which provides control and displays the data plots. I won’t go into more detail here, because all is thoroughly explained on the uTracer web site: https://www.dos4ever.com/uTracer3/uTracer3_pag0.html

There are some incredibly slick uTracer builds on the above the site. Mine is pretty bare bones by comparison, but still did it’s job very well.

Recapping Can Capacitors in Antique Electronics

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The number one component failure in antique electronic devices is old electrolytic capacitors. Most troublesome are the “can” type multi-segment capacitors. These are hard to find and can be quite expensive. More importantly, even if you find a replacement, it’s likely to be “old stock” and not certain to last since the some aspects of their “clock” started ticking when they were made, not when you start using them.

My approach has been to “re-cap” failed can capacitors with modern capacitors of equal or better ratings. This is cheaper, and also more reliable as long as high quality caps are used. Many think this can’t be done without cutting or damaging the can and impacting the appearance of the equipment. This would, of course, not be desirable in equipment where the can caps are visible, such as old McIntosh power amplifiers.

The rest of this post will show how to re-cap cans so they look completely original when done.

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Philips 212 (GA212) Turntable Upgrade

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I still have a Philips 212 turntable that I bought new around 1974. This turntable is a classic from the heyday of affordable, but high quality, Hi-Fi gear.

Philips 212 turntable. A classic from 1971.

Over the years, my 212 developed all the ailments familiar to owners of these machines. The main power switch failed, and then the touch buttons stopped working. This post details my repair/modification project.

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Renishaw MP11 CNC Probe on a Tormach Mill

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There are many CNC touch probes of varying quality available for the Tormach. The two offerings from Tormach are a “passive” probe for about $250, and a “digitizing” probe for $1250. I opted to buy a used Renishaw probe on eBay in an attempt to get the quality and performance of a digitizing probe, but for less than the price of the passive probe.

The cost of used probes on eBay vary all over the map, but I got what I thought was a good deal – a Renishaw MP11 for about $150. My eBay probe came with no cable (more on that later) and had a 1/2″ straight shank, but I figure those shortcomings would not be too hard to rectify.

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MP11 with shop-made TTS adapter

It turned out that my MP11 “deal” was less “great” than I thought because of the “outer diaphragm” issue, which I later found out is common with old Renishaw probes. There are supposed to be two rubber seals that surround the stylus base and keep out dirt while also sealing in some secret oil that prevents corrosion of the contacts. The seals look like tiny gear-shifter boots. They are described (somewhat) in the MP11 manual, starting on page 1-16:

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Adding a VFD to an Odd-Duck Milling Machine (Enco 100-1525) Motor

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Fig 1.VFD box wiring

A while back, I got a nice deal on an early 90’s Enco 100-1525 milling machine. It’s a Chinese 2/3 size Bridgeport copy with an 8″x32″ table. This machine has a 3-phase motor, which I consider a plus because it means I can have knob-controlled speed by adding a VFD (Variable Frequency Drive).

Adding a VFD is usually not too complicated with typical two-speed three-phase motors, but this machine turned out to have a 4.3-to-1 speed ratio between the two ranges (unlike the typical 2-to-1 ratio). With a 2-to-1 ratio, it’s usually fine to run the motor only on the high speed range and then use the VFD for speed reduction. There is a small torque reduction at low speeds when doing this, but for home shop use, it’s fine.

But with the Enco mill motor’s 4.3-to-1 ratio, if I only drive the high speed motor coils and then try to dial down the speed to cover the slow range, the torque loss is too much. This meant I had to keep BOTH motor speed ranges and devise a way to switch between them.

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