Electronics > Metrology

Valhalla 2701c schematics + firmware V3

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lowimpedance:
 After searching high and low there appears to be no schematics for the 2701c online. So having located a paper copy I will add here the schematics plus the parts lists and any other extra info that is not already uploaded, including a dump of the firmware, as I get the spare time.
To start with we have the Main PCB with the parts overlay and useful notes plus the relevant schematics.
Additional is the option I-T2 120mA option schematic.

One thing that I have not found answered yet is the firmware different for units with the current option installed or is it all the same and there is a jumper or link on the main PCB that tells the system it is present  :-//. A possible hint might be from the GPIB option where on the schematic there is a pin on the header connection to the main PCB, (pin 20), called IEEE FIT tied to 0V which pulls down a pin on a 6821, (pin 16 portb), when plugged in. So perhaps the firmware just checks a logic level for the current option too !.

Edit:1. added display and GPIB schematics + comp overlays.
       2. Had a good look on the main PCB and schematics and it looks like there is no test for the current option so its most likely a firmware difference, pity.
           I noted that the firmware from a 2701c with the current option was obtained but had not been uploaded, in this thread :
           https://www.eevblog.com/forum/metrology/tear-down-valhalla-2707a/msg941497/#msg941497
           Would be nice to try the firmware for the current option one day !.



lowimpedance:
 Mechanical drawings and Parts list.

quarks:
thanks a lot for sharing this documents

just in case anyone missed it, have a look at a very nice video from Shahriar Shahramian (aka Hugoneus) "The Signal Path"

https://www.eevblog.com/forum/testgear/teardown-repair-calibration-of-a-valhalla-2701c-programmable-precision-source/msg840669/#msg840669


TiN:
lowimpedance, we missed your threads indeed.  :-+

lowimpedance:
Lastly we have the ROM firmware from the 2701c with bonus pic of the label and the programmer read showing the correct checksum as per the label  :-+.

Please note this binary file is for the 2701c with NO current option. Also the unit does not have the GPIB option either but I'll wager the firmware contains that function and does a check at power on.
Displaying a "no IEEE" message during the startup test on the unit here. (must test that theory by shorting to 0V pin 20 on the header socket).

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