TEK 2445B main capacitor replace?

[ingvar]

I am in the process of re-capping the power supplies of a Tek2445B and a Tek2465B. My question is this: The two 290μF 200 volt main caps test good on my ESL tester. They measure at 313.8μF 0.09ESR and 311.5μF 0.07ESR. The date codes say they are 31 years and 33 years old. Should I replace them or leave them alone? How much life is left in them? What is the consensus on this forum?

[squadchannel]

i think they are in good condition, but not expensive.

I would replace them all caps.

[MarkL]

I don't think you're going to find a consensus opinion on replacing capacitors just because they are old (aka "recapping").

My opinion is to leave them alone unless they are determined to be bad through troubleshooting, visual inspection, or direct testing.  Some manufacturers, such as Tektronix, provide AC ripple specifications for DC power rails which can help determine if replacement is needed for the main filter caps.

One exception in the 24xx series scopes is the RIFA capacitors near the AC input on the power supply board.  It is not uncommon for them to explode due to age and take other components with them.  Be particularly suspicious if they are severely yellowed and/or show signs of cracking.  You can search around for recommended replacements on this forum and others such as https://groups.io/g/TekScopes.

[H713]

My rule is that I only replace capacitors if I have a good reason to believe they're bad or getting close.

If the caps (or the PCB in that area) show signs of running very hot for long periods of time (PCB darkening, yellowing or shrinkage of the plastic covering on the cap, etc. The only other time I'll replace them no matter how well they test is if I'm dealing with high-hour equipment in a mission-critical application.

Otherwise, leave them alone. It's really quite rare that I see big snap-in caps fail unless it's a really harsh application, which this isn't.