[Milsurplus] TV-7 Calibration

[Mark J. Blair]

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

It covers 0.1 through 111,111,111 ohms.


-- 
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/