I have a VR4000D on the bench, powers up (draws around 35-40a to power up then idles at 5a at 13.6v) has rail voltage of 179vdc across the rectifiers and also have the +/-9vdc for the output driver cards as well as +/-87vdc. No output what so ever, power supply fets switching at 27.3khz.
Am assuming problem is in the daughter boards. I can get readings for the IC.
Am assuming problem is in the daughter boards. I can get readings for the IC.
Have you tried operating all of the pots and switches through their entire range with a signal source connected and a speaker connected to the dead channel to see if the channel ever produced any sort of sound (even if it was just static/noise)?
Do you have rail-rail oscillation on the outputs?
Is there any modulation of that oscillation when a signal is driven into the amp?
Is the relay engaging?
Do you see any audio reaching the header on the driver board?
Is there any modulation of that oscillation when a signal is driven into the amp?
Is the relay engaging?
Do you see any audio reaching the header on the driver board?
Do you have rail-rail oscillation on the outputs? How can I check?
Is there any modulation of that oscillation when a signal is driven into the amp? How would I check?
Is the relay engaging? Yes
Do you see any audio reaching the header on the driver board? No
Is there any modulation of that oscillation when a signal is driven into the amp? How would I check?
Is the relay engaging? Yes
Do you see any audio reaching the header on the driver board? No
Do you know how to use it? (Note no intention to degrade you, only know your skills).
180V rail to rail or to ground? Seems too high voltage for an audio amp using solid state.
180V rail to rail or to ground? Seems too high voltage for an audio amp using solid state.
Yes I know how to use it (and trust me I understand you asking, not offended in any way).
180 across the rails, 89.5 -/+ from ground.
180 across the rails, 89.5 -/+ from ground.
Rail to rail osccillation:
https://www.bcae1.com/repairbasicsforbcae1/repairbasics.htm#rtoroscillation
Modulation would make the pulse width of the r-r oscillation on the output transistors vary when a signal is driven into the amp.
If you're not seeing a signal reaching the board, I'd expect a break in the signal path.
https://www.bcae1.com/repairbasicsforbcae1/repairbasics.htm#rtoroscillation
Modulation would make the pulse width of the r-r oscillation on the output transistors vary when a signal is driven into the amp.
If you're not seeing a signal reaching the board, I'd expect a break in the signal path.
Would the signal be on pin “FB” of the driver board or pin “IN”? Not getting any audio signal in either.
I'd expect the IN pin.
I don't think it's true for this amp but it's possible to see no input signal if the signal directly feeds an inverting input on the driver board. I think the input for this board goes to a 1k resistor.
You stated that you checked for signal with a dummy load. Are you sure that you didn't miss something since you couldn't hear it? the noises/signal are sometimes very brief when they are going through an intermittent connection.
I don't think it's true for this amp but it's possible to see no input signal if the signal directly feeds an inverting input on the driver board. I think the input for this board goes to a 1k resistor.
You stated that you checked for signal with a dummy load. Are you sure that you didn't miss something since you couldn't hear it? the noises/signal are sometimes very brief when they are going through an intermittent connection.
I had the scope on the dummy load when I was messing with the switches and pots. Am pretty certain I didn’t miss anything but I’ll go ahead and hook a sacrificial speaker to it and check again.
Amp has both protections “on”. Will switch over to off and give that a shot.
Amp has both protections “on”. Will switch over to off and give that a shot.
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You don't need a sacrificial speaker. Connect the speaker through a 40w incandescent lamp. If there is a spike, the lamp will absorb the power. If you want a bit more protection, insert a 100uf (value not critical) non-polarized capacitor inline with the speaker as well.
Square wave looks fine. It is weird that the amp is protected but still switching. Does this unit posess a remote input and properly wired?
Osvaldo- it is not in protect, it has protection circuits with tabs to engage or disable. Does have a remote input, yes wired properly on my bench.
Can you inject a steady sine (filtered line signal suffices) wave into the amp's input and trace it until the PWM chip?
Osvaldo- am using a sine wave generator and follow the trace/signal right after two op amp (quad 74). Don’t see it going to the driver boards.