HPAK 3458A Capacitor Replacement

[Ole]

Hi there,
I have a 1999-2000 Unit that is approaching the end of its current calibration interval and I took note of the "wet" Capacitors inside:
Electrolytic Capacitors:
A1:
A2:
A3:
A4:
    C7,C8:    2200µF  35V     0180-4033   16,5mm dia. 32mm long       (1189-2253-ND)(DK)
    C9          15kµF    16V     0180-4034   36mm dia.    26mm long       (493-8615-ND)(DK)
    C10-15:  1µF        35-50V              Hermetic
    C17:       22µF      50V     0180-3913   8mm dia. 16mm long            (1189-50YXM22MEFRT15X11CT-ND)(DK)
A5:
A6:
    C1,C11    680µF     50V     0180-4032   16mm dia. 21mm long         (493-1914-ND)(DK)
    C200-01  47µF       63V     0180-3828   8mm dia. 12mm long           (P19619CT-ND)(DK)
    C8           8300µF   35V     0180-3898   25mm dia. 67mm long axial (493-8635-ND)(DK)
    C202       330µF     25V     0180-3830   10mm dia. 12mm long         (1189-1891-ND)(DK)
    C203       220µF     16V     0180-3829   8mm dia. 12mm long           (493-14723-1-ND)(DK) or (1189-4157-1-ND)(DK)
A7:
A9:
Tantalum Capacitors
A1:
    C3:          3,3µF   15V      0180-0210   Hermetic
    C17:         1µF     35V      0180-0291   Hermetic
    C20/21:    2,2µF  20V      0180-0197   Hermetic
A2:
    C211:   15µF    20V     0180-1746   Hermetic                              (399-11291-ND)(DK)
    C701-706 "                          Hermetic
    C709-710 "                          6,5mm dia. 12,5mm long                (1189-50YXM22MEFRT15X11CT-ND)(DK)
    all caps except C702 and C704 are hermetic, those are 22µF 50V
    Al-Electrolytic Nichicon
A3:
    C146/47 15µF    20V     0180-1746   Hermetic
    C181      33µF    10V     0180-0229   Hermetic
    C303    "
    C353    "
    C250/51 4,7µF   10V     0180-0309   Hermetic
    C252/53 4,7µF   35V     0180-0100   Hermetic
A4:
A5:
    C150-55 1µF     35V     0180-0291   Hermetic
A6:
    C2           6,8µF   35V     0180-0116   Hermetic
    C4           2,2µF   20V     0180-0197   Hermetic
    C105         "
    C304         "
    C12         4,7µF   35V     0180-0100   Hermetic
    C406/07  1µF      35V     0180-0291   Hermetic
A7:
A9:

I will add the digikey or mouser part numbers for replacement caps soon.
One more thing, does anyone know the lead spacing on A4C9, I forgot to measure that...
Cheers,
Ole

Edit: This is list is not yet finished, so if you think that a capacitor doesnt fit please let me know

[Ole]

Here is a link to the full version of the Capacitor Cart,
it includes both the hermetic tantalum version of the capacitors on A2 and an electrolyte replacement
although the replacement version is not axially leaded...

https://www.digikey.de/short/89rnpjz2

[Kleinstein]

The hermetic wet tantalum capacitors should not need a replaement, unless they are really bad. They are very reliable, but quite expensive parts. So many a cost reason why they are hardly used, maybe for military of aviation. 

[Ole]

In my case A2C702 and A2C704 are populated with 22µF 50V Al-Electrolytics and based on the CLIP(https://xdevs.com/doc/HP_Agilent_Keysight/3458A/doc/3458A%20CLIP.pdf)
Those should be 15µF 20V hermetic Tantalums as well.
So I would be replacing the Al-Electrolytics with hermetic Tantalums.

[Ole]

My idea for replacing the big outguard cap (A6C8) are:
-Using a Radial Cap and bodging the wiring

-Using two caps in parallel (399-11637-ND)(DK)

-Using a cap with a lower time rating than (1572-1675-ND)(DK)

[Kleinstein]

I see not real need for the wet tantalums.  C702 and C704 are just at the supply, before a regulator. So any low ESR type should be OK.
I would not expect that the meter to be used at temperatures well below freezing  - one of the few reasons to want tantalum capacitors.

[Ole]

I´ve removed the tantalums and put in a few more options for the A6C8 replacement:
https://www.digikey.de/short/5pww8vcn

[leighcorrigall]

This post would be more useful if your board revisions were presented. For example, A4 REV B has an extra aluminum capacitor designated C17. My unit has an A4 REV A installed, and I would like to confirm C07, C08, and C09 without opening the covers. I would also like to know the lead spacings, independent of looking up each candidate's part number.

I don't think you need to replace the tantalum capacitors. The aluminum capacitors are the most important because they tend to age. Depending on the load, they can age faster and compromise the board when leaking out.