Two of the output are not oscillating. As it comes out of protection one set is oscillating the other is not. Diodes d33-34 read 00.00v when tested?
Do you have the 90 volt rail? You will see this on the Drains of Q103 & 203, measured from the Power Ground Terminal.
Check the voltage ladder circuit, ZD3-12v, ZD4-24v, ZD5-12v. If the three zeners don't add up to 50 volts, one of the zeners is bad or there is a bad SM cap across the zeners. C61,C62 0r C63-100nf 0805 ceramic caps. Change all three with 50v caps or better.
D33 and 34 tie back to the protection circuit.One of the 1N4148's may be shorted and cause the amp to be in protection. If this is the case, replacing them may fix the protection issue.
If you remove the diodes you may discover a pair of 16 ohm 2watt(?) 2512 SM and a 25 ohm resistors near the speaker terminals burn up.This is caused by an oscillation on one channel, not to be confused with the PWM carrier for the Class D circuit. There are 2 22nf caps in the feedback loop for each channel and if they fail they feedback to much signal causing a 90 volt oscillation. The caps are C129,130,229,230, also C131,231-3.9nf caps may need to be replaced. If you replace the caps before removing D33,34, you may save the 16 ohm resistors mentioned earlier.
Check the voltage ladder circuit, ZD3-12v, ZD4-24v, ZD5-12v. If the three zeners don't add up to 50 volts, one of the zeners is bad or there is a bad SM cap across the zeners. C61,C62 0r C63-100nf 0805 ceramic caps. Change all three with 50v caps or better.
D33 and 34 tie back to the protection circuit.One of the 1N4148's may be shorted and cause the amp to be in protection. If this is the case, replacing them may fix the protection issue.
If you remove the diodes you may discover a pair of 16 ohm 2watt(?) 2512 SM and a 25 ohm resistors near the speaker terminals burn up.This is caused by an oscillation on one channel, not to be confused with the PWM carrier for the Class D circuit. There are 2 22nf caps in the feedback loop for each channel and if they fail they feedback to much signal causing a 90 volt oscillation. The caps are C129,130,229,230, also C131,231-3.9nf caps may need to be replaced. If you replace the caps before removing D33,34, you may save the 16 ohm resistors mentioned earlier.
Yes I have the 91vdc of rail present. So.im.moving on to the other suggestions now. Thanks as always, u are most helpful with these amplifiers. With only remote and ground the amplifier cycles through amprage. .08-.10-.32.50 ect....
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The d33-d34 are shorted, the resistors r175 is a 27R is reading kohms (out). All the 16ohm resistors are in tolerence, reading 4.5ohms in curcuit.
Well it was working after replacing d33-d34. Output and all and while I was checking the voltages on the ladder the lead slipped and brought down the 470uf 50v cap that is top side. And I don't know what else. But it lost audio output. I pulled and checked the 470uf I brought to ground and it's fine. I lost the sawtooth wave form.
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What is the locator number for the 470uf cap? C67 perhaps? You may have taken out ZD7-11v zener, tied to the PWM (sawtooth).
Have you rechecked the ladder circuit? The sawtooth circuit needs 12 volts from the ladder circuit.
Have you rechecked the ladder circuit? The sawtooth circuit needs 12 volts from the ladder circuit.
I beleive it took out the zd7 I didn't know what to replace it with. And I will check the ladder again. I went through the the caps and diodes real quick but it was late so I shut it down. I I'll recheck everything today.
So the audio is back but it looks a like something else is off bill. Just not as clean of a signal as it should have.
Are you looking at the output?
Do you have a clean sawtooth? If you can measure the frequency it should be approximately 100khz
post any screenshots of the PWM & sawtooth IC11-Pins 3 & 5, IC11-Pins 1 & 7
and input to output inductors-L101.201 and spkr terminals with and w/o signal
Do you have a clean sawtooth? If you can measure the frequency it should be approximately 100khz
post any screenshots of the PWM & sawtooth IC11-Pins 3 & 5, IC11-Pins 1 & 7
and input to output inductors-L101.201 and spkr terminals with and w/o signal
ZD5 supplies 12 volts for IC9-sawtooth generator. because the waveform is present at IC11-Pins 3 & 5, ZD5 is okay.
ZD4 & ZD5 supply 36 volts for IC11. Because you have a good PWM squarewave at IC11-Pins 1 & 7,this ladder portion is okay.
That leaves ZD3-12 volt zener, which works with ZD4-24 volt zener, for IC10, which should have 36 volts between Pins 4 & 8. If ZD3 is bad or shorted or the 100uf cap is bad, you will not see any signal from IC10-Pins 1 & 7, whoever the input should still be there.
I'm wondering if the preamp is not passing signal. Recheck the ladder circuit , by going across each zener separately. If all voltages are present 12v-24v-12v. start tracing the signal through the preamp to IC10.
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