Have a Kenwood KAC-9104D that powers up and has output but draws high current and cuts off when played moderately. The power supply feeds it 13.65v which pulls down to 11.7v when the amp switches on. The output inductor gets hot at idle. The PS Gets gates have 4.46v on each bank. The rail voltage is ±69v. Legs 1-3 reads 5.0v on positive outputs, and 5.2v on the negative outputs. Across the speaker outputs reads 700mv. I have tried a different known good inductor with the same results. I am posting pics of scope readings at various locations, with probe grounded to GND terminal.
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Did something burn near the center of the board?
Is the heating equal at all points around the inductor?
Is the heating equal at all points around the inductor?
There may have been a sticker or something on the board previously but the black residue wiped off with acetone. The inductor seems to be evenly heated all around. Touching it would cause me to pull away my finger in 2-3 seconds from anywhere around it. The one I swapped in behaved identically.
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Can that scope accurately display a square wave of 40kHz+?
Do you have a clean square wave on the output of IC7? No audio input.
Do you have a clean square wave on the output of IC7? No audio input.
Are you driving audio into it? If so, remove the audio.
Align the trace to the reference line and use 5v/div.
Align the trace to the reference line and use 5v/div.
With a speaker connected, is there any sound from it?
Do you have a clean triangle waveform on pin 1 of IC6?
Do you have a clean triangle waveform on pin 1 of IC6?
Yes, there is clean audio from the amp. Posting a scopeshot of the speaker terminal. I placed the board back in to check for audio. I will remove it again to check for the triangle wave on pin1 of IC6.
The problem with this amp was that it drew higher current than normal, and it cut off when trying to raise the volume.
The problem with this amp was that it drew higher current than normal, and it cut off when trying to raise the volume.
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Earlier, you stated that there was no audio being driven into the amp. The signal seemed to be modulated. That's why I asked if there was any output (of any sort) from the amp... with no audio being driven into it.
I'm assuming that that's music and not a sine wave. Is that correct?
I'm assuming that that's music and not a sine wave. Is that correct?
There was no audio/signal being input to the amp before now. The shot from the speaker terminal was audio, but that same waveform was present with the music playing and with the RCAs unplugged, just that when the music plays it vibrates/shakes but the waveform remains the same.
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Make sure that you're seeing the actual v/div that you're marking the photos with. For example, the triangle waveform should be about ±4v.
Repost the previous 2 images but connect the scope ground (the scope probe's ground clip) to pin 3 of IC6 (or any close ground) for the triangle waveform photo. Ground the scope to the negative speaker terminal for the speaker output waveform.
Repost the previous 2 images but connect the scope ground (the scope probe's ground clip) to pin 3 of IC6 (or any close ground) for the triangle waveform photo. Ground the scope to the negative speaker terminal for the speaker output waveform.
The settings that are marked on the pics are the settings I have to use to get the complete waveform displayed and about three cycles. The triangle waveform cannot be displayed completely when set to 5V/div, not even at 10V/div. Only set at 20V/div can the complete top and bottom of the waveform be displayed.
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on 5v/div, if you touch to the 12v supply, do you get a deflection of just over 2 major divisions?
The 9104 doesn't have waveforms but the 9103 is very similar and does have waveforms. Look at pin 1 of IC32 (same as IC6). The triangle wave shouldn't swing more than about ±4v.
The 9104 doesn't have waveforms but the 9103 is very similar and does have waveforms. Look at pin 1 of IC32 (same as IC6). The triangle wave shouldn't swing more than about ±4v.
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I don't understand what you mean "touch to the 12v supply". If I touch the B+ terminal with my finger, there is no change. Not sure what I should be touching, and with what...
The B+ terminal of the 12v power supply that you're using to power the amp. Touch it with your scope.