I got a HP 3457A in good condition for reasonable price at ebay.
It performs nicely, but I thought it would be a good investment to retrofit the 30 year old electrolytic caps for power supply rails, the mains input filter and the battery for calsettings.
For others who want to retrofit this equipment too, here is what I have done:
I turned it apart to see in what condition the unit was and I was really surprised how good it was.
No dust, no visible aging and the best: battery changed in 2009
No battery change needed for the next 10-20 years - nice!
Battery replacement would be really critical, as it holds the calsettings and the replacement method is not so easy...
It turned out, that there are only four caps inside with standard sizes, so no worry about:
3300µF 7,5mm (digital board)
1000µF 7,5mm (analog board)
2x330µF 5mm (analog board)
I replaced them with Panasonic FR series caps (105°C 10.000h lifetime), this should last for the next 30 years - even at higher temperatures
The sizes are not critical, because today you get the same or even better ratings at half the size, so only the lead-wire spacing has to match.
It would be possible to replace with higher capacitance at same or smaller sizes.
The old caps are still in tolerance, but as lacking of an ESR-Meter, no further investigation is possible.
The mains input filter from Schaffner has bad reputation as there are multiple reports of blowing or burning units and as there is no fuse in front of it, this is really a critical component.
I replaced it with a Schurter 6A type (Schaffner has 3A) with matching component values, but its a bit longer in size.
It turned out that there are no problems with cable length or other components with this size, but it could be a little problem if you leave the 3300µF cap...
X2: 47nF
Y2: 2.2 nF
L: 0,8mH (Schaffner 0,75mH)
Now the unit is refreshed and reliability is improved.
The HP 3457A is very nice featured for its age - I like it!
What do you think:
What could be other reasonable retrofit for getting better reliability?
And for getting better performance?