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Hi,
I hope someone with more knowledge of SMPS or experience of this particular mixer can help.
I'm trying to repair a Peavey XR1212 powered mixer.
Symptom is that when switched on, the LED's all light up, then a click is heard and the unit is dead.
I've had some success in the past with fixing SMPS, but no luck on this one.
It has a class D power amp on the same board, with a ribbon cable going off to the mixer section.
I can't find any shorts on any of the output rails, or electrolytic caps.
I've tried replacing the little temporary power supply cap which kickstarts the driver chip, as I know these sometimes fail.
Interestingly, if I unplug the ribbon cable to the mixer, and power on, the relay will click a couple of times, but then hold in. I can then hear a regular, very quiet ticking, as the SMPS is attempting to start, and a mosfet (Q5) and MJM317 (U2) (which were physically bolted together) get rapidly very hot. I luckily have a thermal imager, which is handy sometimes.
I've also replaced these two and IC13, as it's close and associated with the circuit.
No luck though, the symptoms persist. I don't really understand enough about SMPS to be able to work out why these devices are getting so hot, so hopefully someone can guide me.
I think I've attached the schematic correctly - here's hoping.
Ewan
I hope someone with more knowledge of SMPS or experience of this particular mixer can help.
I'm trying to repair a Peavey XR1212 powered mixer.
Symptom is that when switched on, the LED's all light up, then a click is heard and the unit is dead.
I've had some success in the past with fixing SMPS, but no luck on this one.
It has a class D power amp on the same board, with a ribbon cable going off to the mixer section.
I can't find any shorts on any of the output rails, or electrolytic caps.
I've tried replacing the little temporary power supply cap which kickstarts the driver chip, as I know these sometimes fail.
Interestingly, if I unplug the ribbon cable to the mixer, and power on, the relay will click a couple of times, but then hold in. I can then hear a regular, very quiet ticking, as the SMPS is attempting to start, and a mosfet (Q5) and MJM317 (U2) (which were physically bolted together) get rapidly very hot. I luckily have a thermal imager, which is handy sometimes.
I've also replaced these two and IC13, as it's close and associated with the circuit.
No luck though, the symptoms persist. I don't really understand enough about SMPS to be able to work out why these devices are getting so hot, so hopefully someone can guide me.
I think I've attached the schematic correctly - here's hoping.
Ewan
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