Refurbished HP400C VTVM...my newest toy
 

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. :yes:

Cheers,
Rob

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Great find. I luv the old HP VTVMs1

Me too. One of these days, I want a 400D or H, and a 410 series.

Looks good! Now to remove that red sticker on the panel...

I have an extra HP400D and a HP-410B if anyone is interested.

And a 200CD and a 201B.

thats in awsome condition ,i like it great score.

Thank fellas.

LOL I put that on. Homemade decal with the instument's specs at easy access. The paint was stained there under it. :banana:

Round 2 with another one. I'm getting addicted to the 400 series.
It's an old '50s boat anchor and I had to do a lot of restoring but I got it cheap.
It seems to be dead-on accurate clear down to 500 microvolts and up to almost 3 MHz in frequency. (Even though it's rated to only 2 MHz.)

New tubes and replaced the paper and electrolytic capacitors and any resistors that measured out of tolerance. Lots of contact and chassis cleaning. I repainted the face and cabinet. (The little white numbers and letters were a b*tch.) Fabricated a new leather handle out of an old black leather belt.

Kind of a fun project, and I'm happy to have it.

cheers
Rob


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Nice work!

Thanks man!

Nice! I just picked up a HP 400HR in beautiful condition. Love these HP VTVM's. I have seen restuffed cans wrapped with trimmed Red Bull cans

Cool! Got any pictures of it yet?


(I since did get a 400H. It needed very little work other than cleaning.)

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And collected and restored a few more things:

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Another "C":

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And an FET meter:

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