MTX 81000D LED 238 does not turn on and no audio

[Mjimenez]

a square sign. I had to move the gain potentiometer to send a signal and the same signal is reflected in the gate of fets 245~248 and in the gate of fets 255~258 -76v

 

[Perry Babin]

If the scope is isolated from the main supply, ground the scope probe ground clip to the source leg of the FET and recheck the signal.

Do you have a 0.01uf film or ceramic capacitor?

 

[Osvaldo de Banfield]

Square wave looks good. In pin 1 and 2 of UC3845 there is only DC and a bit of noise.

 

[Mjimenez]

if I have capacitors on both sides and I can't see any signal

 

[Perry Babin]

Do you still have signal on the output of the 5532?

 

[Mjimenez]

Yes i have. insisting these signals appeared, it has a hum in the PS fets and consumption of 0.9 amps

 

[Perry Babin]

You need to ground the scope probe to the source pad of the FETs? << Only if the scope is isolated from the mains.

 

[Mjimenez]

Yes

 

[Mjimenez]

Bad news, the D260 diode and the capacitor next to the 1000uf capacitor opened, what value is the j5 zener (D260)?

 

[Perry Babin]

If it actually opened, the optocoupler that it was regulating for, may have failed.

MMSZ5250

Confirm that size is right before ordering.

 

[Mjimenez]

If it actually opened, the optocoupler that it was regulating for, may have failed.

MMSZ5250

Confirm that size is right before ordering.

Thank you, I already managed to get the diodes and the 3120 I have again the signals in the high and low side gate with a 0.1uf capacitor, in the end it was the resistance of r287 and the one of 100 ohms that is below d252, d260 and d253 and a 1000uf capacitor at 35v.

 

[Mjimenez]

If the scope is isolated from the main supply, ground the scope probe ground clip to the source leg of the FET and recheck the signal.

Do you have a 0.01uf film or ceramic capacitor?

Maybe from here I got confused, could you enlighten me how to make this connection?

 

[Perry Babin]

You connect the capacitor across the gate and source pads and then check the signal.

 

[Mjimenez]

Good morning, these signals are the ones I get with the 0.01uf capacitor

 

[Perry Babin]

Were the scope tip and ground connected directly across the capacitor for these waveforms?

 

[Mjimenez]

Were the scope tip and ground connected directly across the capacitor for these waveforms?

Yes

 

[Perry Babin]

I see the problem. The only signal is the 45Hz input. Do you have a signal generator that you could use to inject a square wave of at least 20kHz?

 

[Mjimenez]

yes, I will do it

 

[Perry Babin]

Do you know where to inject it?

 

[Mjimenez]

Veo el problema. La única señal es la entrada de 45Hz. ¿Tiene un generador de señal que podría usar para inyectar una onda cuadrada de al menos 20 kHz?

I'm sorry, my device doesn't do that function