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What do these caps do in the circuit? Worth replacing?

toroechado

toroechado

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Greetings to all!

I'm upgrading a pair por Harman Kardon HK775 mono amps and I'm replacing the caps in the sgnal path with Wima caps.

Is it woth replacing the caps I mark on the schematic too? What do they do? I haven't seen caps like these in other amps I've worked in and not sure if worth using Wima or regular electrolytics here.

Thank you!

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Those are "speed up "caps. At high frequencies (fast rising signals) they supply current to the output and keep the driver transistors from going into shut off (base capacitance of the outputs increases drive current at high frequencies) Keep them. IElectrolytics are best with low ESR. Film caps work fine, but are big, expensive, and hard to source at that value. They are equivalent to caps across the emitters of the drivers in some circuits.
 
It looks like the caps, (10uF 16V) AC couple the bases of the transistors to which they are connected, since the value, at 10uF, is quite large.
 
Thanks! So the best option is to replace them by high quiality low ESR electrolytics? No point in going film?
 
Film caps would mean recapping will not be needed next time a recap happens, but a10uF film cap is pretty big.
 
Between 4,7uf and 12uf are about the most annoying values to replace these days, especially at low voltage. It's to big for film, to small for elco's. Unless it's anything special you will probably end up with some 50v elco. It'll do.
 
The schematic shows they are polarized, so you would want to go with polarized electrolytic capacitors. If my memory serves me correctly film capacitors are non-polarized or bi-polar.

Larry
 
You can always use a non-polar cap where a polarized cap was used, but films are probably impractical here. I'd replace 'em because lower voltage caps tend to fail faster than 25+ volt caps. Digikey has about 26 different 10 uF 25 V Nichicon caps that could be used, most of which are under a buck. I'd match the lead spacing and go for long life parts.
 
The Nichicon UPW series are a great option. High temperature and high ripple current. You can get them in almost any lead spacings which is easy for replacing them, just like Conrad mentioned earlier.
When in need of small capacitors I tend to use the Nichicon UVR or UVZ series. They are smaller and great too.
 
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