Hi together,
my DD SS1B burned, because i think im a dumbass. To less current...
The PSU blow on one side.
On the picture you see the blown gate resistors.
I disassembled all fets in PSU section, also the rectifiers.
I have a clean signal on both sides on the gates.
If i mount a fet on the left side, the PSU works, if i mount a fet on the right side, the fet gets instantly hot, the PSU drop more than 4 amps.
But i don´t understand where the current goes.
The TL494 is replaced to a KA7500B, same result.
my DD SS1B burned, because i think im a dumbass. To less current...
The PSU blow on one side.
On the picture you see the blown gate resistors.
I disassembled all fets in PSU section, also the rectifiers.
I have a clean signal on both sides on the gates.
If i mount a fet on the left side, the PSU works, if i mount a fet on the right side, the fet gets instantly hot, the PSU drop more than 4 amps.
But i don´t understand where the current goes.
The TL494 is replaced to a KA7500B, same result.
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i had it on a amp, that the windings from the transormer hasnt good contact to the board, so that the +12v on the fet on one bank was missing. This had the same effect.
I will try it again.
Found the Problem with the high current. I replaced all transistors around the TL494.
Amp works with only one fet on every side. No rectifiers installed.
Then i reassembled all Parts, only new ones.
Amplifier starts up fine, plays music.
When i disconnect the remotewire, the problemside from the PS blows again.
Only when i disconnect.
broken Zeners?
Thanks
Found the Problem with the high current. I replaced all transistors around the TL494.
Amp works with only one fet on every side. No rectifiers installed.
Then i reassembled all Parts, only new ones.
Amplifier starts up fine, plays music.
When i disconnect the remotewire, the problemside from the PS blows again.
Only when i disconnect.
broken Zeners?
Thanks
Does it ever blow the FETs when there are no rectifiers in the circuit?
Did you replace/check all of the gate resistors and driver transistors?
With your scope, very closely monitor pins 3 and 4 of the 494 when powering down. Does pin 4 go below ground? Set the scope on DC coupling, 1v/div and 2ms.
Did you replace/check all of the gate resistors and driver transistors?
With your scope, very closely monitor pins 3 and 4 of the 494 when powering down. Does pin 4 go below ground? Set the scope on DC coupling, 1v/div and 2ms.
Rectifiers installed -> Fets blown after take remote away.
All gate resistors and driver transistors, including TL494 are new.
But i will recheck them.
Scope measurements i will do now
All gate resistors and driver transistors, including TL494 are new.
But i will recheck them.
Scope measurements i will do now
What kind of diode is on top left? Think its a zener. But what it will do there?
Transistor is one of the drivers from the PSU-Mosfets.
Diode is between emitter and base.
The other 2 ones sitting between ground and PWM-Signal.
I think one of them is broken, so when i shut of the pwm-signal, the Mosfets gets killed from high voltage.
Transistor is one of the drivers from the PSU-Mosfets.
Diode is between emitter and base.
The other 2 ones sitting between ground and PWM-Signal.
I think one of them is broken, so when i shut of the pwm-signal, the Mosfets gets killed from high voltage.
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The attached diagram may be similar.
In the attached diagram, C24 drives pin 4 low when the 5v supply is pulled down too quickly. This can cause the IC to change modes from push-pull (normal) to single-ended. Removing or significantly reducing the value of C24 will allow you to see if it still tries to blow FETs when you remove remote voltage.
In the attached diagram, C24 drives pin 4 low when the 5v supply is pulled down too quickly. This can cause the IC to change modes from push-pull (normal) to single-ended. Removing or significantly reducing the value of C24 will allow you to see if it still tries to blow FETs when you remove remote voltage.
Measured two times, with and withuot cap.
My 70N06 Fets are empty, i have to look for equivalents that i have.
My 70N06 Fets are empty, i have to look for equivalents that i have.
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I think it is possible i get a bunch of **** 70N06.
I tried it now with P60NF06 and they dont blow.
But i´m not sure, if 22 Ohms gate-resistors are ok for them.
I tried it now with P60NF06 and they dont blow.
But i´m not sure, if 22 Ohms gate-resistors are ok for them.
Set the timebase to 10us, not 10ms and set the vertical amplifier to 5v/div. Repost the images with those settings.