Power Supply Bypass Cap?

[patfont]

Hi,
Looking for some help on adding a bypass cap to my Marantz 2220B Power Supply Board I am working on. What jumpers should it go across and what value cap should I use. Please see Pic of board etc. below: Click on image to enlarge.

[agdr]

A little more info, please, on what you are trying to achieve here. Does it have a problem right now or are you looking to just buff something up?

If you are asking about a high frequency bypass capacitor across filter electrolytic(s) then that is typically a 0.1uF ceramic across C803, C804, or both. If there is room/clearance on the bottom of the PC board you could solder the 0.1uF's directly across the electrolytic pins there. C803, R801, and C804 are forming a CRC filter going into the regulator.

Something like these:

http://search.digikey.com/scripts/Dk...=478-3146-1-ND (Digikey)

KEMET|C330C104K1R5TA|CAPACITOR CERAMIC 0.1UF 100V X7R | Farnell United Kingdom (Farnell)

This type of bypass solves the problem of the electrolytic having a large(r) series inductance which increases impedance at higher frequencies. The ceramic has a low inductance. There is no polarity on ceramics, of course (no + lead). You can solder it in either way across the electrolytic pins.

[patfont]

Originally Posted by agdr

A little more info, please, on what you are trying to achieve here. Does it have a problem right now or are you looking to just buff something up?

If you are asking about a high frequency bypass across filter electrolytic(s) then that is typically 0.1uF ceramic across C803, C804, or both. If there is room/clearance on the bottom of the PC board you could solder the 0.1uf's directly across the electrolytic pins there. C803, R801, and C804 are forming a CRC filter.

Something like this:

http://search.digikey.com/scripts/Dk...=478-3146-1-ND

This type of bypass solves the problem of the electrolytic having a large(r) series inductance which increases impedance at higher frequencies. The ceramic has a low inductance. There is no polarity on ceramics, of course (no + lead). You can solder it in either way across the electrolytic pins.

Hi, thanks for the taking the time to look at this for me. There are no problems, I am restoring this unit and am now working on the power supply board and was just looking for any tweeks I could perform to help the sonics of this unit even if it is something small. I will use your suggestion on C804.

[agdr]

Sounds good! I just added a Farnell number too. Just a standard disk ceramic 0.1uF rated 100V or above would work just fine also.

[DF96]

The best place for a bypass, if you feel one is necessary, is the amp board not the PSU board.

[Ron AKA]

I think I would go with a 0.47 uF metalized polypropylene cap. You have a voltage regulator so it may help more after the regulator than before, or do both. You could also upgrade the two main caps by increasing them 50% in size and looking for a low impedance design. The Panasonic FM or FR would do for a 680 uF and 50 volts. A Chemicon KZE would do in the 63 V location.