Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums > Pro AV Forum

Crossover replacement part Deux

<< < (2/3) > >>

Art Welter:

--- Quote from: Jason L Holland on March 15, 2022, 09:46:16 PM ---Great advice. Anyone know of a guide to testing components? I have a good multimeter but not great knowledge. :)

I assume if I find the bad component then I could get it at digikey or somewhere like that?

Thanks again for your replies

J

--- End quote ---
The PCB should be simple point to point resistance, near "0" ohms.
The coils should read a low resistance, probably under 1 ohm. If they don't look burnt, the value in MH is of no concern to you. If you need to replace one (one is in parallel with the HF (tweeter), one in series with the LF (woofer) you will need to measure the working unit with an LCR meter, or find the value from a schematic.
The 25W (watt) and 10W resistors should read within J=+/-5% of their nameplate resistance "R", 2.7 ohms (2R7) or 4ohms. One is in series with the HF, one in parallel.
If the series resistor is open, the HF will be dead.
One capacitor is probably in parallel with the woofer.
The other two capacitors pass signal to the HF.
Capacitor testing:
https://www.electronicshub.org/how-to-test-a-capacitor/?msclkid=1b991b4ba54a11eca61267ee33686e85

With some clip leads, a signal source, and a speaker, you could "jump" over any component and find which does not work, narrowing down the search, as Paul mentioned, likely an open capacitor or resistor.

Art

Jason L Holland:
Thanks for the reply. I'm finally able to dig into this.

I did switch the crossover from the known good speaker to the non working speaker and confirmed that the problem is in the bad speaker's crossover.

Do the components I'm testing need to be desoldered from the pcb to test? I imagine so?

Thx!







--- Quote from: Art Welter on March 16, 2022, 01:36:24 PM ---The PCB should be simple point to point resistance, near "0" ohms.
The coils should read a low resistance, probably under 1 ohm. If they don't look burnt, the value in MH is of no concern to you. If you need to replace one (one is in parallel with the HF (tweeter), one in series with the LF (woofer) you will need to measure the working unit with an LCR meter, or find the value from a schematic.
The 25W (watt) and 10W resistors should read within J=+/-5% of their nameplate resistance "R", 2.7 ohms (2R7) or 4ohms. One is in series with the HF, one in parallel.
If the series resistor is open, the HF will be dead.
One capacitor is probably in parallel with the woofer.
The other two capacitors pass signal to the HF.
Capacitor testing:
https://www.electronicshub.org/how-to-test-a-capacitor/?msclkid=1b991b4ba54a11eca61267ee33686e85

With some clip leads, a signal source, and a speaker, you could "jump" over any component and find which does not work, narrowing down the search, as Paul mentioned, likely an open capacitor or resistor.

Art

--- End quote ---

Steve-White:

--- Quote from: Jason L Holland on March 15, 2022, 09:46:16 PM ---Great advice. Anyone know of a guide to testing components? I have a good multimeter but not great knowledge. :)

I assume if I find the bad component then I could get it at digikey or somewhere like that?

Thanks again for your replies

J

--- End quote ---

You could also find an electronics technician in the area and let them do it.  A crossover will require non-polarized electrolytic capacitors which are a specialty item.

Paul G. OBrien:

--- Quote from: Jason L Holland on April 16, 2022, 04:39:45 PM ---Do the components I'm testing need to be desoldered from the pcb to test? I imagine so?
--- End quote ---

Lifting one side of the component from the circuit board is usually sufficient. The 3 components on the lower left side of the board in your pics appear to be for the HF driver, that is the white 10W2R7J resistor, the immediately adjacent yellow capacitor, and the smaller of the two inductors. I'd start by just heating and reflowing all the solder joints on the components as a cold(cracked) solder joint is a common problem. If that doesn't fix it start with the resistor and lift one side out of the PCB, these are prone to cracking internally and becoming open circuit. A quick test with the multimenter on the ohms setting should tell you if it's good or not, it should measure about 2.7 ohms. The capacitor will measure open circuit on the multimeter, it's unlikey it is bad unless it's physically burnt so you may have to change it to know for sure. The coil should meansure as a dead short, if you don't get that it's bad but this would be the most unlikely failure.

Jason L Holland:
Thanks all. I've already reflowed the solder joints so I don't think that was it.

So I'll start with the small resister then move on to the other HF components. Quick questions...

So by what you're saying the cap isn't measurable it will just show open? Maybe just replace it? Digikey?

I get a dead short on the coil but how would that show on my multimeter? Open and zero resistance?

Thanks again! If I can't find the issue with these quick tests I'll take it to a electronics guy. Anyone know a good place in Atlanta?

J



--- Quote from: Paul G. OBrien on April 16, 2022, 07:19:43 PM ---Lifting one side of the component from the circuit board is usually sufficient. The 3 components on the lower left side of the board in your pics appear to be for the HF driver, that is the white 10W2R7J resistor, the immediately adjacent yellow capacitor, and the smaller of the two inductors. I'd start by just heating and reflowing all the solder joints on the components as a cold(cracked) solder joint is a common problem. If that doesn't fix it start with the resistor and lift one side out of the PCB, these are prone to cracking internally and becoming open circuit. A quick test with the multimenter on the ohms setting should tell you if it's good or not, it should measure about 2.7 ohms. The capacitor will measure open circuit on the multimeter, it's unlikey it is bad unless it's physically burnt so you may have to change it to know for sure. The coil should meansure as a dead short, if you don't get that it's bad but this would be the most unlikely failure.

--- End quote ---

Navigation

[0] Message Index

[#] Next page

[*] Previous page

Go to full version