Valhalla 2724A resistance standard manual

[jfphp]

Hello,
Iam looking for the schematic diagram of the relay board located underneath the main PCB. I found nothing in the various manuals available on the net. I point out that my instrument SN 36-2199 has no Aromat relays on RLC, D... but reed relays AD1A05 from American Relays. Nothing in the Errata, update section of the manual. Thank you.

[ManateeMafia]

I tore my house apart looking for the manual. Turns out I never bought it. 

I did the next best thing and took a few photos of my calibrator. I don't have a separate board under the main pcb. I also have the CPR option if that makes any difference.
The quality isn't the greatest but I can send better photos if you like.

My serial number isn't that far off but the year of manufacture is ~1983

[lukier]

Wow, interesting device. I always assumed it would be something like Fluke 5450A (i.e. a bunch of relays and resistors), but here on the photo I've noticed a LM399, which seemed odd.

So I started reading the theory of operation from the manual and it is very interesting. It is just 6 reference resistors, the rest are analog control loops to draw current and provide the correct voltage drop - I guess not dissimilar to a DC load in the CR mode (chepos implement that in the microcontroller, some Agilent loads use analog multipliers).

I would never think that with such technique the specs can be so good - for 10K: 90 days 7ppm + 50 uOhm, 1.5 ppm tempco. Actually, not much worse than 5450A.

Thanks for the photos.