Hi fellow social distancers, Got two Skar RP 2000.1D in for repair. Both in protect. Power supply runs. No shorted outputs. Pulled all the outputs to see if it made a difference. No change. The protect circuit is controlled by a 393 comparator chip. Just to be sure I changed the 393 chip. No change. Can anyone shed some light on the protect circuit in these amps? Thanks
LM393
Pin 1: +5.2V
Pin 2: +5V
Pin 3: +8.5V
Pin 4: Gnd
Pin 5: +2.5V
Pin 6: +2.2V
Pin 7: +5.2V
Pin 8: +14V
LM393
Pin 1: +5.2V
Pin 2: +5V
Pin 3: +8.5V
Pin 4: Gnd
Pin 5: +2.5V
Pin 6: +2.2V
Pin 7: +5.2V
Pin 8: +14V
There is more to the protection than the 393.
Did you have rail to rail oscillation on the outputs when they were in the circuit?
Did you have rail to rail oscillation on the outputs when they were in the circuit?
Thanks Perry. I know to check the rails for noise. Rail voltages are clean. I've never heard of checking rail to rail oscillation. Please explain how to hook up the scope to check that.
I just needed to know if there was activity there.
It looks like your probe may need to be adjusted to match your scope.
Have you tried operating all of the pots and switches through their entire range to see if audio (or anything else) played through?
Was there any modulation of the rail-rail oscillation when you drove a signal into the amp?
It looks like your probe may need to be adjusted to match your scope.
Have you tried operating all of the pots and switches through their entire range to see if audio (or anything else) played through?
Was there any modulation of the rail-rail oscillation when you drove a signal into the amp?
Okay,
"It looks like your probe may need to be adjusted to match your scope." I will look into that.
"Have you tried operating all of the pots and switches through their entire range to see if audio (or anything else) played through?" Yes
"Was there any modulation of the rail-rail oscillation when you drove a signal into the amp?" very little if any.
New information. I only get rail to rail oscillation if the signal ground is isolated from power ground. When common ground I get no rail to rail oscillation. Protect light stays on either way.
"It looks like your probe may need to be adjusted to match your scope." I will look into that.
"Have you tried operating all of the pots and switches through their entire range to see if audio (or anything else) played through?" Yes
"Was there any modulation of the rail-rail oscillation when you drove a signal into the amp?" very little if any.
New information. I only get rail to rail oscillation if the signal ground is isolated from power ground. When common ground I get no rail to rail oscillation. Protect light stays on either way.
Referenced to Speaker negative 0V, Referenced to power ground 9.7V with RCA shield isolated from power ground. O V when RCAs are grounded to power ground.
Do you have any op-amp terminals other than the ones for their power supply pins that have any more than a fraction of a volt of DC on them?
I don't know if those are the problem. I was hoping to find something that could drive voltage to the shields.
Monitor the DC voltage on the collector of Q301 from before remote is applied and continuously for about 15 seconds after remote is applied. What do you see?
Monitor the DC voltage on the collector of Q301 from before remote is applied and continuously for about 15 seconds after remote is applied. What do you see?
Lift Q301 to see what the voltage on its collector goes to.
While it's up, check to see if the amp produces audio.
While it's up, check to see if the amp produces audio.