X2 capacitors for Rivera amps

[Roberto Lasco]

Hi Guys,

Fixed an Rivera Hundred 2 Twelve sometime ago, with a blew supression cap on the PT's HV tap. Schematic calls for a 0.047uF 440VAC, but those caps seem made of unobtainium...at least here in Brazil, although had no luck looking on ebay either.
Just used a regular polyester cap, but now owner complains about radio picking/general interference, and noisier reverb.
Would be that cap so important to affect the reverb circuit ?

250/275VAC types seems more available. Would they work fine (in this supression duty) wired in series ?
What would be a source for them ? (since Riveras blow them very often, stock some would be a good idea).

thanks,
roberto

[doctor]

Hi Guys,

Fixed an Rivera Hundred 2 Twelve sometime ago, with a blew supression cap on the PT's HV tap. Schematic calls for a 0.047uF 440VAC, but those caps seem made of unobtainium...at least here in Brazil, although had no luck looking on ebay either.
Just used a regular polyester cap, but now owner complains about radio picking/general interference, and noisier reverb.
Would be that cap so important to affect the reverb circuit ?

250/275VAC types seems more available. Would they work fine (in this supression duty) wired in series ?
What would be a source for them ? (since Riveras blow them very often, stock some would be a good idea).

thanks,
roberto

You can use capacitor 0.022-0.1 uF of any type, but it’s voltage must be more than 220V (standard AC rms value in Brazil) multiplied by 1.41 (in order to get amplitude value), that is more than 310V.
I prefer 600V. You can find cap at Digi-Key, Mouser, Farnell, etc…

Radio picking and general interference have as a rule another source - bad contact or bad solder point at amp’s input circuitry or GND.

Reverb noise is another story altogether…

[Roberto Lasco]

This cap don't sit in the (wall) AC line (BTW, Brazil is 120V); but shunting the bridge rectifier on the high voltage secondary tap, which sees about 340V. I already used an "any type" cap (polyester, 630V), apparently with poor results...
Rivera construction board won't lead me to think I had a bad solder joint, besides problem seems to arised after this cap change.

So I want to revalidate my questions and add one: what if I use the 250VAC X2 type in the primary of PT ?

[Roberto Lasco]

Just a correction: cap is not a 0.047, but 0.01; and PT primary already use a supression cap...
Found today at ebay those X2 440VAC caps, but at 0.068; would it be suitable subs ? Not sure about the theory behind that supression job. Where's RG when you need him ?