Hello, can someone help me identify why my power supply drive looks like this?
It looks the same all the way back to the MC1 but just with a lower voltage pre-drive buffer.
Rail voltage is too high, 204vdc. Amp comes on with blue light only but no drive on the outputs.
The drive buffer ucc27524 is verified good.
It looks the same all the way back to the MC1 but just with a lower voltage pre-drive buffer.
Rail voltage is too high, 204vdc. Amp comes on with blue light only but no drive on the outputs.
The drive buffer ucc27524 is verified good.
Attachments
The duty cycle is rolled back as far as it can be. The 204v isn't far off.
What's the DCV on the disable pin?
What's the DCV on the disable pin?
DCV on pins 1, 3, 8 and 10 of one of the output drivers?
What do you see on the output of the op-amp that is driven with that resistor (pin 14 of CI7)?
What do you see on the output of the op-amp that is driven with that resistor (pin 14 of CI7)?
Ic2:si8244bb
Pin1: 2.82v
Pin3: 5.05v
Pin8: 5.03v
Pin10: 0.2v
Ic4:si8244bb
Pin1: 3.68v
Pin3: 5.03v
Pin8: 5.04v
Pin10: 0.2v
Ci7: OPA1679
Pin14: audio riding on 7.3vdc
Pin1: 2.82v
Pin3: 5.05v
Pin8: 5.03v
Pin10: 0.2v
Ic4:si8244bb
Pin1: 3.68v
Pin3: 5.03v
Pin8: 5.04v
Pin10: 0.2v
Ci7: OPA1679
Pin14: audio riding on 7.3vdc
+15 on the output or reg4?
+15 on pin 11 of CI1?
Do the voltages on the output of CI1 agree with the voltage on its inputs?
+15 on pin 11 of CI1?
Do the voltages on the output of CI1 agree with the voltage on its inputs?
I do get +15 on the output of REG4, however, I can’t seem to find CI1.
I accidentally discovered I can get a nice 20khz ps drive wave if I drop the supply voltage to appx 9.6v. It will hold the drive wave until I increase the input voltage to appx 11.3v. This doesn’t change the behavior of the output section.
Additionally I have 1.145v of dc offset on the outputs. Not sure that matters since the output fets aren’t oscillating.
I accidentally discovered I can get a nice 20khz ps drive wave if I drop the supply voltage to appx 9.6v. It will hold the drive wave until I increase the input voltage to appx 11.3v. This doesn’t change the behavior of the output section.
Additionally I have 1.145v of dc offset on the outputs. Not sure that matters since the output fets aren’t oscillating.
Attachments
It's an LM319.
Is that offset measured directly across the speaker terminals with a load on the speaker terminals?
If I'm not mistaken, these amps have a regulation that works in steps, not like a linear type controller. The pulse width change was due to a reduction in the rail voltage.
Is that offset measured directly across the speaker terminals with a load on the speaker terminals?
If I'm not mistaken, these amps have a regulation that works in steps, not like a linear type controller. The pulse width change was due to a reduction in the rail voltage.
The voltages on the on the 319 were erratic and solid dc. Swapped it out and the amp is working now.
I thought I checked this already.
Thank you for helping me!
I thought I checked this already.
Thank you for helping me!
So this amp is still giving me fits. Lots of test time but I have dc offset issues.
I can adjust it down within 3mv or so of 0vdc, however, it fluctuates with or without a load connected.
Once I power off and on it may be as much as 200mv off.
The input voltage seems to have a significant effect on the dc offset as well. For example if I set it to 0mv with 13vdc input to the amp, it may be +-60mv at 12vdc.
There also seems to be excessive noise(slightly more than normal) on the output terminals.
Anyone ever experience this?
I can adjust it down within 3mv or so of 0vdc, however, it fluctuates with or without a load connected.
Once I power off and on it may be as much as 200mv off.
The input voltage seems to have a significant effect on the dc offset as well. For example if I set it to 0mv with 13vdc input to the amp, it may be +-60mv at 12vdc.
There also seems to be excessive noise(slightly more than normal) on the output terminals.
Anyone ever experience this?
It holds 14.8v until I turn the input down to 12.5 volts then the output voltage starts dropping quite rapidly.
Well, that's possibly part of the problem.
What's the input voltage to the 15v regulator at 12v and at 13v?
What's the input voltage to the 15v regulator at 12v and at 13v?
At 12.0v there is 16.4vdc at the reg input, and lots of noise on the output.
At 13v, there is 18.4-18.6 fluctuating and the noise is significantly reduced
At 13v, there is 18.4-18.6 fluctuating and the noise is significantly reduced
no I found a bad zener at location D21. Replacing this stabilized the regulator voltage at 15v, however, I still have erratic dc offset and a lot of noise.
I have noticed occasionally the noise will go away and the dc offset will stabilize and allow me to adjust it away.
I’m thinking there may be a preamp issue. If I touch the rca ground with my finger I get a hum on the outputs.
I have noticed occasionally the noise will go away and the dc offset will stabilize and allow me to adjust it away.
I’m thinking there may be a preamp issue. If I touch the rca ground with my finger I get a hum on the outputs.
Does this amp use the UCC27524 as part of the doubler feeding the 15v regulator?
Is the shield of your signal source grounded?
Touching the shield ground of amps will often produce a hum, especially if you have fluorescent lights near the bench.
Is the shield of your signal source grounded?
Touching the shield ground of amps will often produce a hum, especially if you have fluorescent lights near the bench.
Yes it does, however, unfortunately I can’t verify voltages at the moment. I accidentally shorted the rail caps while discharging.
It was around 72vdc when that happened I wouldn’t think that would have hurt anything, however, no it does not power up.
It was around 72vdc when that happened I wouldn’t think that would have hurt anything, however, no it does not power up.