The --
hp -- 428b verification process continues. I'm at the stage when I need AC current to interfere with the measurement. The manual specifies a 35mA AC current, and suggests a device I've not got (yet, this is TEA, right?) so time to go scrounging. Found a modem PSU wall-wart whose weight and size indicated it was linear. Once I'd gotten rid of the advanced regulation circuit, all 4 diodes and one capacitor
![Grin ;D](https://www.eevblog.com/forum/Smileys/default/grin.gif)
, and calculated a resistor (390Ω) it was time for a verification measurement:
![Test Equipment Anonymous (TEA) group therapy thread 862676-0](https://www.eevblog.com/forum/index.php?action=dlattach;topic=81471.0;attach=862678;image)
I'd tacked some lamp cord on for AC mains, using a wonderfully practical madness, known as a
"Safeblock". Quite dangerous and very handy.
Satisfied with the measurement and assembled with a loop (broken up by two unshielded PL259 plugs
![Cool 8)](https://www.eevblog.com/forum/Smileys/default/cool.gif)
):
![Test Equipment Anonymous (TEA) group therapy thread 862670-1](https://www.eevblog.com/forum/index.php?action=dlattach;topic=81471.0;attach=862672;image)
First adjustment done, more to follow.