Found open 3W resistor which was connected between output + and -, soldered 10k, powered with both 21844 enabled and it blowed output transistors. The transistor plastic case flew away. The power supply was limited to 6amps.
Thats expensive.
Thats expensive.
Current limiting doesn't work on an amplifier that charges the rail caps then enables the output transistors. I don't know if that applies to this amp.
For some amp, you can force the output to be enabled at all times. That allows the current limiter to be more effective because there is no energy stored in the capacitors.
If the 12v regulator has dedicated windings on the transformer, you may be able to check the drive signals with the FETs in the board. Removing the rectifiers would prevent the caps from charging.
The high-side would likely need a supply on the 21844s. I use a 9v battery.
If the 12v regulator has dedicated windings on the transformer, you may be able to check the drive signals with the FETs in the board. Removing the rectifiers would prevent the caps from charging.
The high-side would likely need a supply on the 21844s. I use a 9v battery.
I am just thinking how to and what to do now.
Remove outputs and test drive signal after rebuilding again output driver card?
Why it didnt go in protect while each 21844 was disabled.
And it will work when only 4 of the outputs fets will be installed, one per group? Dont want to blow them all.
Remove outputs and test drive signal after rebuilding again output driver card?
Why it didnt go in protect while each 21844 was disabled.
And it will work when only 4 of the outputs fets will be installed, one per group? Dont want to blow them all.
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I would test without the rectifiers. That should be safe. Yes, after rebuilding the driver board.
I don't know why it didn't fail with only one driver IC enabled. An intermittent problem like an intermittently shorted inductor may make troubleshooting difficult. You need to go through all tests with only one IC enabled at a time. Push/pull/twist inductors...
If the problem is an over-current fault, having all of the FETs in the circuit will make the outputs more likely to survive.
I don't know why it didn't fail with only one driver IC enabled. An intermittent problem like an intermittently shorted inductor may make troubleshooting difficult. You need to go through all tests with only one IC enabled at a time. Push/pull/twist inductors...
If the problem is an over-current fault, having all of the FETs in the circuit will make the outputs more likely to survive.
Or there will be no high side drive signal, because there is no carrier/oscillation?
I did not supply 21844 high side with 9v battery. Thats why there is no high side drive signal... For those who dont know how to do it and also reading:
Perry:
I did not supply 21844 high side with 9v battery. Thats why there is no high side drive signal... For those who dont know how to do it and also reading:
Perry:
Also, what glue to do You use for securing parts like output chokes?
Glue needs to be flexible, easy to remove if needed and can stand higher temperatures.
Glue needs to be flexible, easy to remove if needed and can stand higher temperatures.
The method of securing inductors and transformers varies (you can't always use adhesive alone). For the adhesive, I typically use Goop or E6000. I've started using the following adhesive. It tends to set up quicker than the two previously mentioned.
https://www.walmart.com/ip/Aleene-s-Platinum-Bond-Super-Fabric-Textile-Adhesive/17299866
I don't know if any of these are available where you are.
They are easy to remove in some aspects but don't expect to remove it from between windings.
https://www.walmart.com/ip/Aleene-s-Platinum-Bond-Super-Fabric-Textile-Adhesive/17299866
I don't know if any of these are available where you are.
They are easy to remove in some aspects but don't expect to remove it from between windings.
I wouldn't expect the high-side drive to be at the positive rail. What are you using to supply voltage to the high-side of the driver IC?
Do you possibly have a solder bridge between the drain and source of the high-side FETs?
Confirm with a meter.
Confirm with a meter.
Right now cant check the measurements, but picture maybe confusing, because scope V axis is scrolled up to see low-side.
Here is the measurement of the high side gate (9v battery connected at 21844) with scope probe set to 1x
Attachments
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Confirmed all with meter, there is no shorts.
I have in stock 4pcs IRFP460 - can they be used for testing purposes?
I have in stock 4pcs IRFP460 - can they be used for testing purposes?
Is that the only part you have or are you trying to find something that you can use so you don't blow the correct FETs?
I think I'd remove the rectifiers and check the drive signals with the output FETs installed. The loading of the FET gate capacitance will affect the drive signal. The full load of the correct FETs is better than testing with a partial load of FETs.
I think I'd remove the rectifiers and check the drive signals with the output FETs installed. The loading of the FET gate capacitance will affect the drive signal. The full load of the correct FETs is better than testing with a partial load of FETs.
I am saving correct fets.
Best way will be install all 460lcs in place and test it without rectifiers? Thats how i will try.
Best way will be install all 460lcs in place and test it without rectifiers? Thats how i will try.
