Question about cap between PT lugs.

[joesatch]

I'm rewiring my amp to 120V. It has a heyboer power transformer. Between the black (0v) and black/red (240v) there is a .47uf capacitor.  i'm going to change to the black/white from the black/red to use the 120v tap. What is this cap for and can i just move it to the black/white tap? Is this cap for reducing the pop when going to standby? Why is it .47uf and do i need to change that value when switching to the 120v tap?

[shooter]

guessing it's a EU safety thing, normally never find a cap on the primary side on most hobby builds, might find it on an old 2 prong amp

[tubeswell]

You sure it’s a cap (and not an MOV)?

[joesatch]

i guess it's some sort of surge protection, i have no clue.

Digging some more could be a cap for AC filtering

[shooter]

sent 2ducks, came back with this; (from cap data shown)

https://www.iecee.org/dyn/www/f?p=106:49:0::::FSP_STD_ID:1963

[PRR]

It can reduce the POP when refrigerator or elevator motor switches on or off.

[DummyLoad]

You sure it’s a cap (and not an MOV)?

clearly marked .47uF xxxV - volt rating hidden by wire, not a MOV.


--pete

[pdf64]

Don’t think it’s ok to connect any cap with an apparently suitable voltage rating across the mains. It’s a harsh application that parts need special approval for (x rating live to neutral, y rating live/neutral to ground). The PT acts to filter out much of the hash and nasties, so we don’t need to worry about that stuff on the secondary side of things.
Such caps are probably necessary for equipment to meet electromagnetic compliance EMC regs.

[tubeswell]

You sure it’s a cap (and not an MOV)?

clearly marked .47uF xxxV - volt rating hidden by wire, not a MOV.

Yes I see it now. Missed it before

[joesatch]

Well i left it in place and the amp works on the 120v tap. Not sure if i should remove it or not, or if the value needs to be changed. .47uf Rated at 275 volts

[DummyLoad]

Don’t think it’s ok to connect any cap with an apparently suitable voltage rating across the mains. It’s a harsh application that parts need special approval for (x rating live to neutral, y rating live/neutral to ground). The PT acts to filter out much of the hash and nasties, so we don’t need to worry about that stuff on the secondary side of things.
Such caps are probably necessary for equipment to meet electromagnetic compliance EMC regs.

line to line and line to ground caps are to filter RF & other noise on the line. caps are not there for compliance.

 https://www.justradios.com/safetytips.html

--pete

[tubeswell]

Well i left it in place and the amp works on the 120v tap. Not sure if i should remove it or not, or if the value needs to be changed. .47uf Rated at 275 volts

That should be fine unless there's a major lighting strike in the mains and your surge protectors ain't working. (But then everything else that's plugged in and switched on will suffer the same fate)

[66Strat]

I had a lightning ground strike very near my house ten years ago on June 14, 2010. I remember the day because that was the day my Dad died. The lightning fried the neutral wire for the AC. It was hot that day. There was a storm that day. I was at the hospital all day. When I came home that night, no AC, and the house was miserably hot. AC man came the next day to fix the AC. He showed me the burnt wiring. All of the insulation was burnt off of the neutral wire leading from my breaker box to the AC unit. I was lucky that it didn't burn the house down.

[pdf64]

Don’t think it’s ok to connect any cap with an apparently suitable voltage rating across the mains. It’s a harsh application that parts need special approval for (x rating live to neutral, y rating live/neutral to ground). The PT acts to filter out much of the hash and nasties, so we don’t need to worry about that stuff on the secondary side of things.
Such caps are probably necessary for equipment to meet electromagnetic compliance EMC regs.

line to line and line to ground caps are to filter RF & other noise on the line. caps are not there for compliance.

 https://www.justradios.com/safetytips.html

--pete

Err, that’s what EMC is https://ec.europa.eu/growth/sectors/electrical-engineering/emc-directive_en

Equipment has to pass electromagnetic compatibility compliance testing before it’s legal to sell it in the EU.

[DummyLoad]

Don’t think it’s ok to connect any cap with an apparently suitable voltage rating across the mains. It’s a harsh application that parts need special approval for (x rating live to neutral, y rating live/neutral to ground). The PT acts to filter out much of the hash and nasties, so we don’t need to worry about that stuff on the secondary side of things.
Such caps are probably necessary for equipment to meet electromagnetic compliance EMC regs.

line to line and line to ground caps are to filter RF & other noise on the line. caps are not there for compliance.

 https://www.justradios.com/safetytips.html

--pete

Err, that’s what EMC is https://ec.europa.eu/growth/sectors/electrical-engineering/emc-directive_en

Equipment has to pass electromagnetic compatibility compliance testing before it’s legal to sell it in the EU.

i stand corrected. thanks for the link! 

--pete