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

[Penthode]

Great find. I luv the old HP VTVMs1

[VTVM]

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

[bob91343]

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.

[VTVM]

Thank fellas.

Originally Posted by bob91343

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

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

[snelson903]

thats in awsome condition ,i like it great score.

[VTVM]

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

[Notimetolooz]

Nice work!

[VTVM]

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

[VTVM]

Cool! Got any pictures of it yet?


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




And collected and restored a few more things:




Another "C":




And an FET meter: