EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: Traceless on December 12, 2024, 10:19:04 pm
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Hey everyone,
are there any parts lists/schematics for the newer Keysight DMMs (34465A/34470A) available? I found a service manual (https://xdevs.com/doc/HP_Agilent_Keysight/English%20_%202013-12-01%20_%20PDF%209.33%20MB%2034460-90901%20c20140121%20%5B352%5D.pdf) on xdevs, however unlike the 34401A service manual (https://xdevs.com/doc/HP_Agilent_Keysight/service/34401A/34401A%20service.pdf) it is missing the parts/schematics section.
Currently I'm trying to find the exact type/parts number of the parts marked as:
E103 (MOV)
Q101, Q102, Q103
R102/103/120 (<- package type/power rating)
in the bottom left area on this (https://live.staticflickr.com/7286/16171856023_76e95f736e_4k.jpg) picture.
Also I'd like to verify if I'm correct in assuming that Q41X would be MMBT6520L, and D03 on this (https://flic.kr/p/rxxJZW) picture could be an MBRS340T3G.
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so far people managed to get parts numbers in other threads, but no schematics beyond the 34410a 11a series have leaked
maybe it has some similarities .... but reverse engineering must be done ...
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For the large resistors R102,R120,.. it is likely about the voltage rating, not so much the power rating. The size could be measured, of needed even from pictures.
Q101 to Q104 should be high voltage depl. MOSFETs. There are not that many to choose from. BSS129 would be a first candidate.
The MOVs are often labeled and this should be a high voltage type, like close to 1000 V.
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This gives some part numbers, but only those deemed user replaceable. I think it may just be an updated version of the link posted by the OP.
https://www.keysight.com/us/en/assets/9018-03876/service-manuals/9018-03876.pdf (https://www.keysight.com/us/en/assets/9018-03876/service-manuals/9018-03876.pdf)
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@Kleinstein: Looking for BSS129 I mostly find this Siemens Small-Signal Transistor in the TO-92 Package (https://www.alldatasheet.com/datasheet-pdf/view/44781/SIEMENS/BSS129.html). I didn't get any hits for that type on Digikey, Farnell or Mouser, however there are similar type names in the SOT23-3 package, for instance BSS126, BSS127. (https://www.mouser.de/c/semiconductors/discrete-semiconductors/transistors/mosfets/?q=BSS&package%20%2F%20case=SOT-23-3&vds%20-%20drain-source%20breakdown%20voltage=600%20V&NewSearch=1)
@jc101: Thank you for the link, just like in the manual I linked above there is very little information on individual components present. Basically what is missing is the replacable parts starting at p. 127 in the 34401A manual (https://xdevs.com/doc/HP_Agilent_Keysight/service/34401A/34401A%20service.pdf#page=133) and ideally the trailing schematics.
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The FETs in the protection should be depletion mode. So the BSS126 could be OK but the BSS127 not. The BSS126 could be good enough, a CPC3982 would be a 800 V type and I don't see a high voltage one in SOT23.