Refurbished HP400C VTVM...my newest toy

[VTVM]

All done...this instrument is dead nuts accurate and flat responding!

I replaced all the paper caps and 'lytics. One 6AK5 tube was noisy so I put in a new one. There were several out of spec resistors replaced, too. The 2W, 25K B+ potentiometer was frozen and I had to replace that. Other than all that and much cleaning, a new handle and power cord, I just set the regulated B+ and DC filament voltages and went through the calibration procedure.

I also took out the big, finned (selenium, I guess) filament power rectifier and put in silicon bridge and a 2 Ohm, 20W dropping resistor between the bridge and the filter.

This will be a welcome addition to the family. I've been wanting one of these for audio through broadcast band RF work. Huckuva a lot easier to set up than a scope when you just need a dB or voltage level.

For those not familiar with these, they are an AC only voltmeter with a high input impedance. 1mV to 300V full scale, 20Hz to 2MHz. They also have an amplified output (the top terminals by the meter) with a 0.3V maximum output for feeding a less sensitive scope or what have you.

Kind of a "one trick pony" but it does its trick very, very well.

Cheers,
Rob