Nothing in that circuit should be drawing that much current.
What's the DC voltage across the resistor?
Do you have a larger resistor (or a limiter, like a 12v lamp) that you could install temporarily?
Is it still producing drive pulses without the FETs in the circuit?
What's the DC voltage across the resistor?
Do you have a larger resistor (or a limiter, like a 12v lamp) that you could install temporarily?
Is it still producing drive pulses without the FETs in the circuit?
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Drive pulses without fets are good. Checked also with a capacitor g-s,
It's also OK.. I installed a 50w lamp in the b+ line.. Voltage across resistor in this case only 0.1v
It's also OK.. I installed a 50w lamp in the b+ line.. Voltage across resistor in this case only 0.1v
The lamp would go in place of the 4.7 ohm resistor (not yet).
I don't understand how removing the FETs changed the current passing through the resistor. The only current that passes from the left side of the resistor to the FETs is through two 2k resistors. That's not going to cause the resistor overheat. Are you sure that nothing else has changed?
If you can't find anything, reinstall the FETs to confirm that that's what's causing the resistor to overheat.
I don't understand how removing the FETs changed the current passing through the resistor. The only current that passes from the left side of the resistor to the FETs is through two 2k resistors. That's not going to cause the resistor overheat. Are you sure that nothing else has changed?
If you can't find anything, reinstall the FETs to confirm that that's what's causing the resistor to overheat.
I reinstalled the fets.. The drive ic has a softstart function. If I measure across the resistor, the voltage goes from 0. 4v down to 0.1. In the same time, the square wave wants to build up. It looks like, in the beginning, when the duty cycle is very low, it passes the highest voltage across the resistor.. Less voltage with full duty.
I was wrong about the 1k resistors being in series with the drive from the 494.
Is that part of the circuit the same as yours?
Is that part of the circuit the same as yours?
If you mean r22 and r23, no..
Drive board output drive goes directly to base of the driver transistors.
Drive board output drive goes directly to base of the driver transistors.
If the FETs are installed 1/bank as shown in the photo you posted, install the FETs for only one transformer at a time. Does the amp power up normally with either transformer driven (alone)?
If I remove the fets from the transformer with the auxiliary windings , the amp powers up and don't pull current. No audio..
If I remove the fets from the transformer without aux windings, the power supply powers up, but no aux voltage at the drive circuit for the audio part.
If I remove the fets from the transformer without aux windings, the power supply powers up, but no aux voltage at the drive circuit for the audio part.
I disabled one audio bank. Bridge at g-s driver fets. Used a bench supply with higher output. Bridged the resistor, that always burned..
Amp works.. That means, one audio bank is a damaged driver ic... But it still burns me this resistor.
Amp works.. That means, one audio bank is a damaged driver ic... But it still burns me this resistor.
I thought that both drivers worked when you powered up after letting the caps charge. Was that wrong?
Removed the damaged drive board. Now if I power up, a capacitor qp 5 beside the resistor starts smoking...
how this is possible..
how this is possible..
Can you measure the DC voltage across the capacitor (meter probes with correct polarity) as you power up?