MTX 1501D problem power supply

[Perry Babin]

Sorry. Yes, FET471.

 

[yoppi]

Hi

this is what I get with the oscilloscope.

Regards.

 

[Perry Babin]

Please use the 'go advanced' then the 'manage attachements' option to post images.

It should be a pulse that goes from ground to about 30v. Post the DC voltage on all pins of the 8-pin driver IC for FET471.

 

[yoppi]

Good morning from Spain

Do you refer to U450?


Regards.

 

[Perry Babin]

Yes.

 

[yoppi]

Hi

Voltage pins U450

Pin1: 6.18v
Pin2: 0.6V
Pin3: 0.08
Pin4: 2.37v
Pin5: GND
Pin6: 0.24v
Pin7: 12.9v
Pin8: 4.95v

Regards.

 

[Perry Babin]

Post a photo of the pulses on pin 6.

 

[yoppi]

This is the reading of the oscilloscope

 

[Perry Babin]

Please use the 'go advanced' and 'manage attachments' buttons. Posting as you did will wipe all typed text if someone clicks on the image.

Do you have a standard scope?

Why two images for one terminal?

 

[yoppi]

I'm sorry, but I only have Velleman HPS140i. 2 images corresponding to the reading taken in the pin 6

 

[Perry Babin]

I can't understand what you have. The attached image is typically what you should have for waveforms.

 

[yoppi]

Hi

I do not have these waveforms in any of the pins on the U450, or the center pin of fet471.
I replaced the U450, but the problem persists ....

Regards.

 

[Perry Babin]

You should at least have the timing waveform if the IC has supply voltage. I'll have to see if I can find a board here to see what they're using for timing.

 

[yoppi]

Hi

¿voltage feeding U450 needs to work?

Regards.

 

[Perry Babin]

I haven't had time to do any more research on this amp. It may be the weekend before I can do it.

 

[yoppi]

ok, I'm waiting. thanks.

Regards.

 

[yoppi]

Hi guys

I continue with the MTX 1501D. I discovered that if I disconnect the FET 471, pin 6 from U450 has a square waveform. Can it be that some component that feeds the FET471, transistor, diode has short?

regards

 

[Perry Babin]

If the small transformer driven by FET471 is shorted (sometimes happens), it could cause the IC to shutdown in over-current protection. It's also possible that something connected to the output side of the transformer is overloading the IC.

If the transformer is out, connect only the two primary windings with jumper wires to see if the IC shuts down.

 

[yoppi]

Hi guys

With the T471 outside the IC behaves normally. I have reviewed all components near the T471 and have not located anything short.
So I conclude that the transformer T471 is shorted. Could you please indicate what the primary and secondary T471?

Greetings.

 

[Perry Babin]

The primary would be connected between B+ and the driver IC output pin.