Advice Needed On Recapping Power Amp

Timlub, thanks, I might take you on this offer one day - speaker world is foreign territory to me.  As far as amps go, there is nothing wrong in experimenting, especially if you enjoy it and have guru friend.

Well Kijanki,  If you ever need advice in the speaker world, I understand that world  thoroughly.  As far as amps, I'll just stay in the garage.  I've enjoyed doing the few repairs and mods that I've done and to date, I've never damaged anything. So life goes on. I don't call him often for help, but if I ever need him, I've got a guru that is one of my best friends to call on.  All is good in the world. 

Czarivey, there might be individuals who are capable of such Toyota modifications, but I place them in "exceptional talent" category. Friend of my coworker did not like how transmission in his car operated, so he designed and built his own. Certain "arrogance" and great skill are required for that. Rest of us should enjoy what we have, especially when it is really nice piece of high end audio system. There is nothing wrong with caps that match closely original ones.

Well, I guess that I'm a garage operator.... I have always made sure that my rectifiers would handle the current

I've been in garage operation when I was 16, building EL34 100W amplifiers with components I could find around including chassis made of heavy aluminum trays that fish store nearby tossed out, but when it became my profession for the last 40 years I've learned not to do anything that I don't fully understand.  I would like to understand how do you know what peak current thru rectifier is.  Did you calculate it and how, measured it or just used rectifier that seems to be working? Did you consider max ambient temperature or max line voltage?  Did you consider shorted output condition?

Well I always liked extra power until I realized that in Toyota cars and trucks everywhere everything is perfect at any time and can’t be improved without trade offs — that what was just pronounced by my 2002 Tundra 5mt v6 466 kmi all original afrer 23’ camper long haul 1200mi from ski resort.

It was lovely white winter this year!
Would never mind the other one

Polar Bear
(I.e czarivey)

Well, I guess that I'm a garage operator.... I have always made sure that my rectifiers would handle the current, other than that, I've always increased capacitance without fear.  This is the 3rd time that I've worked on my Sumo, a couple of times ago, I replaced its rectifiers. This time I took it to a friends house and  I increased the power supply my self. He has the amp now finishing up a few mods and repairs from a lightening strike. I consider my old friend to be one of the best old school audio engineers ever. He is not as well known as some, but I've been with him rubbing shoulders with some of the best and trust him implicitly.   

It is switching power supply, but unregulated. 

All capacitors are inductive (even piece of straight wire is inductive), some less some more. Electrolytic caps are in "much more" category.  ESI (Equivalent Series Inductance) can be calculated.

Capacitor becomes self-resonant at the frequency at which capacitive and inductive reactances are even - usually <100kHz (very low) for electrolytic caps.  At this Self Resonant Frequency reactances are exactly in opposite phases canceling each other and capacitor is pure ESR resistance.  Above resonance capacitor is more of an inductor then capacitor.

Amplitude of charging spikes is limited by ESR of capacitor, transformer losses and resistance in series (fuse, cable etc).  Lowering ESR of capacitor might increase amplitude of charging spikes beyond maximum current of the rectifier or max ripple current of capacitor.  These things have to calculated (and not just tried), otherwise it is "garage operation".

and yes, I understand the 120hz "primitive unregulated switcher"  is not a switching supply. Sorry if I added confusion.

@kijanki     Not to be argumentative, this is more for me to be informed. First, I've never added capacitance to a switching supply and This is just not how I understand inductance in relation to a power supply cap. 
Inductance would be creating a magnetic field, yet As the capacitor charges, the magnetic field does not remain static. This results in electromagnetic waves which radiate energy away. So the magnetic field dissipates. The cap itself is not inductive. 
So, I can see faulty, weak or under rated rectifiers.  Maybe if you flipped the switch at the exact instance when your ac was hitting its peak in the sine wave. 
Again,  I've done this a bunch.... The first time was in 1980.  Parasound built a chipped amp around a Sanken STK084... I called Dick Schram and he sent me 2 circuit boards, I ended up using an STK086, put higher grade parts in it.  His amp had 4 - 6800 mfd caps in it.  I used a separate supply case with 12 - 6800mfd caps.  That was my first foray into increasing capacitance and wow, what a difference that it made. 

Timlub, Things that look simple not always are.  There is no such thing as "Linear Power Supply", unless Linear means "Unregulated".   In reality it is primitive unregulated switcher that operates at 120Hz and switches at max voltage.  Current from mains is delivered to capacitors in very narrow current spikes of very high amplitude. Amplitude of these current spikes depends on transformer, power cable, ESR of capacitor etc. while width of the spikes depends on the ripple amount that, in turn, depends on the load current (definition of the switcher).  In addition to current spikes charging capacitors you get also very narrow spikes at the peak of the (rectified sine wave) voltage when rectifier starts conducting for a moment in opposite direction to quickly snap back.  To widen this spike there are "soft" diodes (like HexFET), that conduct fast but snap back slow.  I'm trying to show that operation of such primitive supply is not as simple as it seems and the fact that larger cap works means only that safety margin for rectifiers still exists but was reduced and might be very small.  If we believe that designer put unnecessary margin by mistake that's OK, but I would ask him  :)

As for inductance - electrolytic caps are inductive.  Inductance of such cap is proportional to capacitance.  Increase in capacitance means increase in inductance.   Believe it or not, but power supply caps are in series with your speaker (circuit is closing thru them) and their inductance can affect response time.

@rlb61     after all of this, I'm sure that you'll decide not to recap, but as we have all state, not really needed at this point. 

Kijanki,
    I've never claimed to be the sharpest tool in the shed, but as said above, I've done this many times. I have only had positive results.  How do propose that you get parasitic inductance introduced in a properly designed power supply?  The only issue that I can see is a poor excuse of rectifier. As long as you bridge is rated for the current you should be fine and An ideal cap has zero inductance or resistance on its own. 

Going to higher capacitance means also higher inductance hence slower response to rapid current demand.   It will also reduce ripple and that might not be a good thing, since very low ripple, especially when combined with low ESR means very high and very narrow current spikes charging capacitors and that might couple to any inductance in the rest of the circuit.  I would agree with  kosst_amojan and would not try on my own to redesign an amp.  In some cases it might work in other it could make it worse (or damage rectifier).

Bypassing slow large inductive caps with fast low ESR cap might be not the best idea, since it creates parallel resonance circuit that might ring.  Better option would be to get low inductance electrolytic caps (like slit foil type), but they are expensive.  Better yet is not to "redesign" something that works just fine.  There is also an issue of reselling such "improved" amp.

15 year old capacitors, unless they are in very warm place, should be good for another decade.

recap not needed. don't waste time.

Hi   @kosst_amojan    ....  Well, I guess that really depends quite a bit about your transformer first. My knowledge is limited about "Inrush" current.  
To those reading these comments.. In-rush current is the current flow into a product when you flip on the power switch.  It can be quite large.  That is why on some of these old beast of an amplifier, you see the lights dim when you fire them up. 
I am not a indepth as some others, but as I understand it,  the larger the transformer, especially in toroid types are more susceptible in passing current. When caps are idle,  they look like a dead short,  So the VERY IMPORTANT part here is.... The Low esr along with natural wire resistance is the only filter for this current (unless there is a soft start circuit)... I have done this to maybe 5 or 6 amplifiers.  NEVER had an issue.  Each time, the amp sounded better, but I yield to opinions of those in the know. 

I agree that it is very unlikely that you actually need caps replaced at this point, but if you are after a modification that would help. I can see that. I have replaced power supply caps on a few amps with very good results.  
4 things that you need to seek is lowest ESR possible and highest capacitance that will physically fit along with voltage of at least that of the rails of the amp and high enough temperature rating.  
Most supply caps are 85 degree parts.  That should be absolutely fine... If you had a pure class A amplifier, then maybe move up to 105 degree parts,  but 85 degree typically sound great and work well. 
If you have say a typical 10,000 mfd supply cap at 85 degrees and 63volt part.  Look for the highest value capacitance that will fit that meet that 85 degrees and 63 volts(or higher)  
I just replaced the power supply caps in my old Sumo Nine.  It had 85 degree 10,000 mfd 63 volt parts.  Because it is pure class A, I moved to 105 degree parts and found 22,000 mfd, 80volt parts that would fit that ended up having very much lower esr than even the Panasonic caps that I put in there back in the late 80's.  

For any Electrolytics on the circuit board.  Those circuits often would have very much different results change the values,  so other that raising the voltage try to keep the exact values of the caps that you are replacing and all will be fine. 
But again,  none of this should be a NEED for your amplifier. 

As always, Erik, sage advice. Thank you.

Hi OP,

I think you are a little early for a recap, and by the time your amp was made  capacitor quality (i.e. low inductance and ESR) had taken a major leap forward already.

Also, there are no output caps on most SS amps. I would strongly suggest you leave it alone, and trade it for something new if you have the itch to upgrade.

Best,

E