Working on a Fosgate bd1500. It stays in protect when powered up. Power supply is running. I have the +5 volt Sync and the 100khz carrier. When turned on the bd_out (which goes to the output choke to speaker +) is shorting to ground. All power mosfets are good in the power supply and outputs. I have +160 volts on the positive rail referenced to ground and 0 volts on the negative rail referenced to ground. I don't understand what the Latch circuit does or how it works. Any help would be greatly appreciated. Thanks!
U21 is the most likely culprit. If pin 6 is not charging to over pin 5 (5v), the IC may be damaged. It's possible that there is an over-current fault but that's rare if the outputs don't show as shorted.
A couple more notes. This amp doesn't have positive and negative rails. You have to measure the voltage across the red and black wires.
The over-current protection produces a pulse. Without the latch, the over-current protection couldn't keep the amp in protect mode and the amp would continue to try to switch on, possibly causing more damage.
If U21 pin 1 isn't near 9v, it's not in over-current protect mode.
The over-current protection produces a pulse. Without the latch, the over-current protection couldn't keep the amp in protect mode and the amp would continue to try to switch on, possibly causing more damage.
If U21 pin 1 isn't near 9v, it's not in over-current protect mode.
Thanks Perry. Pin 5 is +5 volts Pin 6 is -4 volts. Pin 1 is -8.6. No shorted outputs. 167 volts across red and black wires.
Replaced U21. Protect LED no longer on but amp acts as if it is still in protect. Pin 5 +5 volts. Pin 6 +8.7 volts. Pin 1 -8.4 volts.
Do you see rail-rail oscillation on the output transistors?
Have you operated all pots and switches to see if audio ever player through?
What's the voltage across the red and black wires now?
Have you operated all pots and switches to see if audio ever player through?
What's the voltage across the red and black wires now?
"Have you operated all pots and switches to see if audio ever player through?" - Yes
Voltage across red and black wires +164 volts
Please explain how the test rail-rail oscillation?
Voltage across red and black wires +164 volts
Please explain how the test rail-rail oscillation?
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