Capacitor ID

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I'm fixing a crossover from a PA speaker.

I found a shorted capacitor. I un-soldered the capacitor from the board and checking it with a multimeter indicates almost no resistance.

The capacitor is a small (11/16" or 9mm in diameter) yellow disk. It says, "Mexico" on one side.

On the other side it says:
X|)
-070
AS3J

How many Farads is this?

Thanks,
Lyle.

 

[OLIVE2222]

Hi Lyle,

Mmmh, a yellow disk with few ohms and this marking is maybe not a capacitor but a thermal fuse. Can you post a sharp picture?

Olivier

 

[davenn]

Sounds more like a PTC ( Positive Temperature Co-efficient) thermistor
sometimes called a Polyswitch
These are usually an overcurent device (sometimes overvoltage)

Dave

 

[[email protected]]

Yeah, you guys are right. I'd really like to thank you guys for the help.

So, that's not the problem. I thought it was a thermister myself at first (one big clue was the big 'TH' printed on the board right beside it) but I got swayed after some googling.

The whole back story to this is I accidentally connected the amplifier output to the low output of the of the now non-functioning passive crossover.

The corresponding amplifier input was connected to an active crossover so the frequencies the now-dead crossover experienced in this mis-connected way were 2 kHz and above.

So, I wasn't intending on using the passive crossover at all; it's just in the speaker in case you're not using an active crossover.

How will I figure out what's wrong with it?

Lyle.

 

[OLIVE2222]

Not sure that I catch everything but:

Normally you can connect the amplifier directly to the loudspeaker, knowing that in the case you lose the protection part of the passive crossover. They should be very few components in the passive crossover so maybe it's worth to repair it.
Regarding the frequency range the passive crossover can handle without damages it's should be the whole audio range. But the loudspeakers themselves can maybe suffer from incorrect frequency range. You talk about PA system, is the amplifier intended to drive 4-8 Ohms loudspeakers? Some PA amplifier have high impedance output and need an external transformer to drive the loudspeakers.

 

[[email protected]]

I didn't explain it very well. I'll try again.

The schematic for the crossover:
http://www.carvinservice.com/crg/schematics/s00220H.pdf

The schematic says rev G, my crossover says rev D, so the schematic might not reflect my crossover exactly (in fact, the thermister that I thought was a capacitor isn't on the schematic).

In error, I connected the amplifier to 'low out' on the bottom left of the schematic. The amplifier should have been connected to 'INPUT (hi in)' near the top on the left. The amp was turned on and turned up to quite a high volume (this is a 500 Watt per channel amplifier). Something in the crossover failed. There is nothing obviously burnt in appearance.

The Biamp Switch on the crossover was set to Biamp.

The speaker itself is fine. It's been used many times since.

I guess all I can do is replace all the capacitors since I have no way of testing them (except with an ohm meter which isn't a good test), and just remove everything else from the board (resisters, switches, choke, and 1/4 jacks) and test them with an ohmmeter?

Lyle.