Should I match filter capacitors in an oscilloscope power supply?

[ClifS]

I had a bridge rectifier go south in my oscilloscope power supply. I replaced that and also re-soldered the connector going from the transformer to the high side of the supply. A couple of the terminals were shaky. While I was at it, I thought it would be a worthwhile to change the filter capacitors as well. I original capacitors tested good for capacitance, but they do have some time on them (1985) I have no way to check ESR. There are 2 filter capacitors in parallel. (2200uf 25v +- 20%).When I went to buy replacements they had 3 2200uf 50 volt capacitors, from 3 different manufacturers. All of them test well withing the 20% range, but I'm wondering if 2 of these could be put in parallel with no adverse effects.

Thanks in advance.
Clif

[George Edmonds]

Modern capacitors are much smaller, just buy one 4700 uf at 25V

G Edmonds

[David Hess]

Mismatched bulk aluminum electrolytic capacitors in parallel will work fine.

Modern capacitors are much smaller, just buy one 4700 uf at 25V

It does not matter in this case, however modern capacitors which are physically smaller for the same capacitance and voltage also have lower ripple current ratings.  If the ripple current rating must be preserved, then a higher voltage capacitor or multiple capacitors in parallel should be used.  A higher voltage capacitor might also be used for wider lead spacing or larger diameter to fit better.

[George Edmonds]

WRONG

Most modern electrolytic capacitors are not only smaller but have a higher ripple current rating especially if you use 105C working ones.

It is NOT a good idea to parallel electrolytic capacitors unless they have the same ESR as the lower ESR one will carry most of the load.

G Edmonds

[David Hess]

WRONG

Most modern electrolytic capacitors are not only smaller but have a higher ripple current rating especially if you use 105C working ones.

That has not been my experience.  For old capacitors where the ripple current rating is specified and matters, I have repeatedly had problems finding suitable replacements and have had to rely on increasing the voltage rating and sometimes the capacitance, even with 105C capacitors, to meet their ripple current ratings.

It is NOT a good idea to parallel electrolytic capacitors unless they have the same ESR as the lower ESR one will carry most of the load.

It will not matter in this case because the input capacitors are specified for bulk capacitance rather than ESR or ripple current rating.