advice sought for replacing caps on '70's receiver

[Dan75]

Hi, i'm new here and a beginner in deeper understanding electronics.
I am cleaning a seventies receiver, a Sony STR-6046A.  I noticed that 2 electrolytic caps are starting to bulge.
Because of this is de soldered them and googled them for specs. Nothing found so far. Because I think they are that old, there is no info to be found on the net in
form of data sheets. So I am trying toi understand what is important to look at when one has components that are without specs provided and are to be replaced.
I have this measuring device : MTester.
https://tkkrlab.nl/wiki/MTester


The 2 caps that I took out are Nichicon caps, blue and one has H7314 ( 35V 330uF ) and the other has H7322 ( 25V 220uF ) on it
They're positioned on the PCB with 2 others that seem ok. (no bulging)
I do not know what the ripple current is and how to know if it is important in this case?

Note; I do not have the correct service manual for this type receiver. The one I have (from the internet) does not have the same layout so therefore I do not know if I can use it in any way.

[Dan75]

220uF cap reads; ESR 0,13  Vloss 1,1
330uF cap reads ESR 0,10 Vloss 0,8
Looks ok I think but because these 2 caps are beginning to bulge out, maybe it is time to replace?
The unit has been sitting for years unused prior.

[james_s]

Just get caps of equal capacitance and equal to slightly greater rated voltage and you will be fine. Electrolytic capacitors from 1975 are not going to be anything exotic, general purpose parts will work perfectly fine.

[Dan75]

OK, thank you. Will that account for most if not all vintage audio? Even in audio stage?
Or is it because this receiver isn't a high end make.

[james_s]

For the most part yes. Electrolytic capacitors are imprecise low-tech parts, modern ones are typically much better than old ones, occasionally the ESR is so low that
It causes problems but it shouldn't be an issue in an amplifier. I wouldn't expect to find electrolytic capacitors in the signal path of anything high end.

[TERRA Operative]

Also, if some are bulging or faulty, it's good practice to replace all of the same type while you are there to avoid having to come back again later to replace the ones you missed the first time.
If a few are bad, it's likely the rest aren't far off too.