Capacitor Identification

Headphones

Can any one help?

Should be easy, but...

This is an axial electrolytic, that's marked on the circuit diagram as 220/4 - can't read the value off the case as it's none too healthy...

Normally I'd expect it to be value in uF (this would be 220uF), then voltage rating, but 4?  The rest of the circuit I have sticks to the value/volts convention.   It's a coupling capacitor in an old Berhinger mixer I'm trying to keep alive (rather than afford a new one!). 

ESchap

I've seen them as low as 6v rated as cathode bias caps in old HiFi valve pre-amps, so 4v is not impossible, will depend on position and duty in the circuit.  However, I'd have thought a coupling capacitor would need a much higher voltage rating.

ESchap

Further thought, are you sure it's a coupling cap? 220uF is very high and they would normally not be electrolytic.  Sounds more like a cathode cap.

Danny1969

Is it a passive mixer ? if so highest voltage in the thing is likely to be the op amp rail + - 17V or +48 phantom 

If it's a powered mixer, especially one of the switchmode power supply types then it could be 400V

Good luck if it is a switch mode I've done a couple and they are a right pain to get right

Headphones

Thanks for the thoughts!

This is in an old Behringer MX1604A audio mixer. It's in one of the the stereo input channels, coupling the output of an op amp to the main bus.

Most of the other coupling caps in the thing are 47uF/25V, but this is different.  Not found my way around picture posting yet, or a snap shot of the circuit diagram I have would help (though it's for an 1804, the circuits appear identical here).  The supply rails are 15V.  The next thing it sees is the inverting input of the bus summing op amp.

The mixer is currently assembled, loath to open it until I've got the cap to do the swap, as with all the nuts, screws, connectors, etc it's no short task...

Danny1969

Just use a 35V, that be fine

Headphones

Guessed at 25V to match all the other coupling caps, just opened the case and found that 220/4 is 220uF/6V3!

No idea how that works, either way the 25Vs are way too big for the space, so I've had to order afresh.

The £1.50 for ten doesn't rankle so much as waiting for the post with so many parts across my desk.