[volt-nuts] More Precision Resistors

[Mark Sims]

IET still makes the DB877...  a shiny new one will set you back $6000!   Several vendors sell used ones for $1500-$2000.   There is one on Ebay for $700.  I paid $75 for mine (plus $25 for the Tek divider I used to fix the thing - ESI also made the resistors in it).  It was in really good condition.  I also have a DB655 and a couple of the ESI Kelvin-Varley dividers that use the same cone-centric stack of knobs.

If I just patch the 100K resistor,  all the setting will be under 0.005%.  For around 40 bucks it looks like I can get the 100K decade pretty much perfect.  I could also also tune up the megohm decade with some 100 gohm resistors....

I considered adding a series resistance to get the 0.032 zero ohm bias to 0.10 ohms,  but that would affect the performance of the other ranges.  Also the bias is not a constant value.  It does change some depending upon the path through the switches.  I treated all the switches with Stabilant 22 (magic stuff...  and it darn well better be at $50/5mL) which really helped. 

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I picked up a DB-877 at the De Anza swap meet in the bay area a few years ago. It was grubby but a bargain at $40!
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