RCA VoltOhmyst WV-77E

I bought an RCA VoltOhmyst WV-77E VTVM from eBay. It was a total steal, the meter has already been calibrated and mostly recapped.

There is a small crack on the upper left of the meter movement but I might slap on the WV-97A meter movement. I already swapped the Zero adjust and Ohms adjust knobs.

On the inside I was a little shocked to see an added fuse with a small plastic bag to insulate it so I need to replace that. The Filter cap needs swapping out and there is a Selenium Rectifier so I should change that over to a Silicone Diode. One problem is when you change something like that there will be more voltage going into the circuit since a Selenium Rectifier has a larger voltage drop around a volt or more than a typical Silicone Diode that averages around .7 of a volt.

As for the other RCA VTVM I was restoring I decided to give that up. Reason being by time I would be finished with it I would have replaced just about every part.


DIY signal tracer

To kill time today I whipped up a simple Solid state Signal tracer. Not a typical one that can be found on the web that uses a 1n34a diode and a set of computer speakers. It is my own take of an old school Vacuum Tube but Transistorized.

It uses simple Class A amplification and a simple Sine wave Oscillator. To keep things simple I also included a small Linear Power Supply that outputs 12 volts. The Oscillator uses 9 Volts but a simple voltage regulator fixes that. The Oscillator isn’t a 100% true sine wave but just enough to push out a tone into the Amplifier.

The probe is also very simple. Just a typical .1uF cap to block out DC. You could adapt the typical RF probe to use it as a RF signal tracer.

Here is the schematic. If the weather is far tomorrow I’ll start putting it together.
New-Schematic (1)

This is my first attempt to using a Mosfet as a driver for an Amplifier. So I have no idea how this will work. If anything I can use a 2n3055 or something on those lines if it does not work right.