First recap job with Sansui 8080

[Gvse]

Got a Sansui 8080 and already replaced all the fusible resistors on the driver board F2436. Trying to recap most of the electrolytics. Regarding the power supply filter caps... The existing ones (2 x 6800 uf) both measure good and are measuring above 7100 uf in-circuit. I would like to increase it to close to 10,000 uf.

Can I add a 2200 uf / 100v (Panasonic FCs that I already have) in parallel to the old 6800 uf ones ?

Dont want to replace the old ones unless i have to. I can do new ones a few years down the line. If the ESR of the old ones (because of their age) are higher than the 2200uf, i might end up reducing it or will be close to what i have currently. Any suggestions ?

 

[Lavane]

I'm not sure paralleling caps for the main filter cpas is a great idea, especially with two different values.
Be carfull upping the cap value for the main filter caps as well. Make sure the power supply can handle it. The added inrush could stress things like the rectifier. When I do, I tend to keep it within 10% or so of the original values. If it's a piece of equipemnt I plan on keeping long term, I do like to do a full recap. Just because I don't won't to have to fo back in for another repair later.

 

[HPMguy]

Parallel caps are not simply additive, although in a filter cap in the power supply it probably won't matter. I wouldn't do it though, and caps as old as those likely are will not really perform to spec under load.

There is a persistent myth that manufacturers always used smaller caps than "necessary" to save money and that putting monster capacity caps in the main power supply will "improve" the sound. Old high ESR caps will indeed diminish the volume required to clip the amp because they cannot provide enough current to hold the voltage, but remember they are being re-charged 120 times a second! the factory installed caps will provide the full rated output of the amp before it clips when new, and more uFs will not increase the clipping voltage past what the factory ones will.

Massive increases in filter cap capacity can fry the rectifier on startup -- double the capacity will essentially double the current draw and forty year old diodes may not do well with that. You can replace them with higher current rated ones to prevent issues, but it will still make no more difference in the output than if you put the original sized (new) caps in.

Bigger ones will not always fit, either.

Now, that said, I have a couple amps with dual voltage output, and three sets of main filter caps that are more or less in parallel, but there is some rail switching and high/low voltage outputs as well. I do often up the voltage rating, but usually only when I can't get the original rating or I feel it was too close to the operating voltage. 75V main caps seem to be going away, so I use 80V instead -- usually still smaller at the same capacity as the originals.

 

[El Rubio]

My rule of thumb when replacing electrolytic caps is to basically change out for the same uF or max of 20% higher. Higher voltage rating is not a problem and sometimes helps new caps fit size-wise. I tend to increase voltage rating on all smaller value caps to make ordering and sorting simpler. For example, if i need 4 47uF 10v & 2-47uF 16v, I’ll order 6 at least 16v but typically bump up to minimum of 25v. Like most folks here, I will replace small value caps in the signal path with film.

 

[Gvse]

Thanks everyone for the suggestions. I will go with the new ones for the filter caps. The main reason for thinking about bumping up the filter caps is based on the discussions here - https://audiokarma.org/forums/index.php?threads/large-filter-caps-for-sansui-8080.951342/ and couple of other forums. Some of them swear they heard a difference . Appears like most of them were able to get away without upgrading their diodes.

Regarding the other caps, i am going for film for anything less than 2.2 uf and going for higher voltage rating (at least one level up) from the original.

 

[rothwellaudio]

Regarding the other caps, i am going for film for anything less than 2.2 uf and going for higher voltage rating (at least one level up) from the original.

Not a bad idea, but what kind of film? There's a big difference between a polyester film and a polystyrene film. And there's a difference between metalised film and film-and-foil. "Film cap" is a pretty vague generic term.

 

[Lavane]

I usually just go with polypropylene film caps for the small value caps. For coupling caps I sometimes use foil-and-oil, or Russian PIO's.
For the smaller value caps, Wima stack films and Panisonic polypropylene caps are usually the brands I use if they are replacing radial electrolytic caps. They come in various lead spacings.

 

[Gvse]

I should have done more research on the film types before ordering.. Ordered the PET Metallized - Stacked type. I guess that is a type of polyester. I can reorder from digikey.. It shows mainly polypropylene and Polyphenylene Sulfide (PPS) types. As Lavane suggested i can go with the polypropylene types.

 

[Lavane]

I tend to replace polyester caps with polypropylene caps in many cases.

 

[HPMguy]

WIMA MKS or Kemet R82 series are fine for signal coupling and decoupling to replace electrolytics. Huge difference between old electrolytics and WIMA caps, very small comparative difference between metalized PET and polypropylene except that the PET will fit and the polypropylene is larger and may not.