[Milsurplus] TV-7 Calibration

[WA5CAB at cs.com]

Change 3 covers ZM-16B/U.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 04/29/2013 10:41:27 AM Central Daylight Time, 
nf6x at nf6x.net writes: 
> On Apr 29, 2013, at 08:24 , Ralph Cameron <ramcam at magma.ca> wrote:
> >The cal. procedure for the TV-7 tube tester lists ZM-16U, resistor, 
> decade ,TM-11-5102 as one of the needed pieces of test equipment. Are these 
> available surplus anywhere or does anyone have one for sale. I expect it is a 
> standard decade resistor box from 1-1Megohm but haven't seen a description 
> of it.
> 
> If my memory serves me correctly (don't bet any money on that!), you'll 
> need the resistor box or some other way to try out fixed resistor values with 
> earlier TV-7 machines. If you happen to have a later model TV-7D machine, 
> then there are potentiometers for the calibration adjustments, and I don't 
> think the decade resistor box is needed to calibrate them.
> 
> I calibrated my TV-7D back in 1999 or so, and I couldn't get the 
> adjustments to converge initially. After much head-scratching, I figured out that 
> the calibration procedure was written for a VOM with 1,000 ohms per volt 
> impedance, and my fancy DVM with its high impedance didn't load the circuits 
> enough to make the measurements come out right. I wrote about this pitfall 
> way back in the day:
> 
> http://www.nf6x.net/1999/01/tv-7-tube-tester-alignment-hints/
> 
> A google search for "ZM-16 decade resistor" turns up plenty of pictures, 
> as well as a PDF copy of its technical manual:
> 
> http://www.liberatedmanuals.com/TM-11-5102.pdf