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| HP 5316A Teardown and Frequency Standard |
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| Kjo:
--- Quote ---5315A prefix 1832A through 2032A have A1R12 factory adjusted for 3.0 --- End quote --- Interesting, as that is the termination/reference bias source for the MRC high speed signals from the channel input conditioners. My 1928A service manual has A1R12 (287 ohm) in the collector of Q2 Colpitts onboard crystal oscillator. R15 is the adjustment pot for the 3VDC supply. I think the onboard oscillator went away with the switch in series 2XXX+. I wonder if the part numbers for the MRC are different. I have only ever seen one part number. |
| aeg:
Oh, there's an inconsistency in the 1832A manual. The reference designators shown in the adjustments section don't jive with those in the schematic. There are no reference designators printed on the PCB itself. The MRC is 1820-2139 in the 1832A parts list, but it changes to 1820-2312 in the 2120A parts list. |
| Kjo:
Interesting,,, I've only ever seen MRC 1820-2312 labeled parts. My earliest meter is a 1928A series. In the late 1970 this MRC may have been a challenge for HP to mfgr with yield. It was a bipolar chip with everything from ECL to IIL inside. My paper manual 1928A (1979) has those grey-over photos with part reference designators printed over certain parts. Double check your parts list though. My list says 1820-2312 for HP part number (col 2) but 1820-2139 for Mfgr part number (Col last). It lists HP (28480) as Mfgr. Dont know why HP would use 2 different numbers for same part, but # on package has seemed always 1820-2312. |
| aeg:
1832A and 2120A series parts lists have matching "HP" and "manufacturer" part numbers. I guess for 1928A they decided to compromise. 1820-2139 labeled parts do exist in the wild: https://www.flickr.com/photos/anachrocomputer/43289590070 (not my photo). 2120A manual also has modification notes for substituting 1820-2312 for 1820-2139 in early units - see one of the 05315-90021 scans, p. 117 or p. 118 depending which scan you have. |
| Kjo:
@aeg Thanks for that confirmation photo! |
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