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More on the NOS Hickok 209A

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Author Topic: More on the NOS Hickok 209A  (Read 410 times)
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« on: August 16, 2017, 04:29:56 PM »

If anyone wants pictures, I will post some.

Well, this beast came to me in an original box, which I saved.  Open it up, and it is 1951 all over again!

It lit up nicely, but would not zero on ohms, AC, or DC.  It had been sitting in a closet for some time.

I looked at the schematic, and decided to try something.  With the meter out of its case, and the mode switch in AC,  I rotated one of the 2 pots on the top left. It has to do with 6AL5 contact potential, but also seems to have some sort of balancing effect.  Suddenly, the meter needle came off of left pegging! I put the zero pot in the mid-range position, and tweaked the internal pot until the needle came close to zero.  I tweaked some more until I could zero on all ranges, from 3 VAC to 1200 VAC.

To my surprise an delight, the beast was now zeroing on DC+, DC-, ohms, and caps!  Wowser!

I found two more pots, both on the bottom of the chassis, and both tough to reach.  These I identified as the DC and AC calibration pots. 

Using 3 9 volt batteries in series (Measured with Fluke 87 Mark III) as a calibration source, I set the beast right on the money on the 30 volt scale.  I then proceeded to test it on all DC scales from 3 volts to 1200 volts. My IP-2717a entered the fracas.  In all cases, the 209A was spot on......1% or less compared to the Fluke DMM.

The story of the ohm meter was similar. I had a glom of Shallcross Acra-ohm pieces, and put them to good use.

On AC, I have yet to set the calibration.  Nonetheless, it is already within 5 or 10%.  I did check the peak to peak function, and it works nicely.  I have yet to test it on a capacitor.

All of this with the original bottles, electrolytics, postage stamp micas, paper caps, etc.  Some times you just get lucky. Yes, many of these "danger" components will soon go, along with those pesky phone tip jacks.

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