Anyone knows the TEN DB-44 Amplifier ?

[enter]

Hi

I have in my hands from a friend the amp mentioned at the title and it is faulty.

When i connect 12V on it the mosfets BUK456 goes very hot in some seconds.

Attached for anyone that wants to help i have the amps interior .
The second photo below shows the mosfets in red mark witch is hot


Best Regards
George

 

[Perry Babin]

How much current was it drawing when you powered it up and the FETs were heating up quickly?

 

[enter]

Hello

In about 5 seconds the amp draws 1.6 A and the FET'S start heating(not very hot ).No speakers connected or any input at rca connectors. Only power supply 12V

This time it produces a strange sound from a part on pcb. It sound like a whistle at high frequency. Maybe i didn't hear it yesterday.
If this helps the voltage at the source of buk456 is 4,7 Volts and the gate are 7,5 Volts(at startup measure 11 volts)

I was afraid to leave the amp with power connected more than 10 seconds.

Any idea what produces this strange sound? Maybe the big coil in front of the FETS ?

Thanks alot for your interest

 

[Perry Babin]

Are you sure that you have the proper pin configuration on those FETs? The gate should be about 5v. The drain (center leg) should be at the highest voltage. The Source leg should be very near 0v.

If you twist the transformer while it's on, does the current draw decrease?

Have you checked the output transistors to see if any are shorted?

If you remove the rectifiers, does the amp power up normally with significantly less current draw?

You should clamp the FETs back to the heatsink before applying power.

 

[enter]

Hi

I am so sorry i typed it wrong. The voltages on the FETS are:
source 0 V
Drain 7,5 V
Gate 4,8 V

If you twist the transformer while it's on, does the current draw decrease?

Can you please make this more clear for me? I must revers the 12V power supply voltage on amp?

Have you checked the output transistors to see if any are shorted?

I checked them with multimeter at diode position and they seem to be ok

If you remove the rectifiers, does the amp power up normally with significantly less current draw?

rectifiers are the parts that look like transistors with diode inside ?

You should clamp the FETs back to the heatsink before applying power.

Yes i will power on with heatsinks

Thanks again and sorry for the inconvenience


Best Regards

 

[Perry Babin]

Grab the transformer with your hand and twist it back and forth a bit. Do NOT reverse the voltage.

The rectifiers are the large components positioned between the output transistors and the power supply FETs. You only need to do this if the current draw remains high when twisting the transformer.

 

[enter]

I am using a computer power supply for the 12 Volts connected to the amp. This is the one i must twist ? Or the part on the amp with red mark i have at the photo below?

 

[Perry Babin]

The transformer is the round component with the wires wrapped around it in the square.

 

[enter]

Ok. I will try it tomorrow and keep you posted. It is a bit late over here
Very appreciated for your help

 

[enter]

Hi

I twisted the transformer and the amperes on power supply remains high.
I removed the two rectifiers and the amp doesn't power on. The sound from the transformer remains and i think it is a bit louder with rectifiers disconnected.

Below at photos i have for you is the transformer and some AC Volts measurements i did at the rectifiers.

Is it possible the transformer is faulty ?

Best Regards
George

 

[Perry Babin]

Post the voltage on the three legs of one of the power supply FET.

 

[enter]

Is this you need ?
DC Volts at Buk456 FETS ?They are located beside the rectifiers.

This measurement below is from one of the FETS
source 0 V
Drain 7,5 V
Gate 4,8 V

I am asking because i have posted this above.
Must i measure another part ?
Opposite are located four P30N6

 

[Perry Babin]

Were these taken AFTER you removed the rectifiers?

 

[enter]

Without the rectifiers on pcb the Voltage is:

source: 0
drain 7,5
gate 4,8

 

[Perry Babin]

The power supply is up and running.

Reinstall the rectifiers and power the amp up for a few seconds out of the heatsink. Do any of the large output transistors heat up?

 

[enter]

They are all cold. No heat

 

[Perry Babin]

Are the rectifiers shorted?

If you measure the DC voltage across the outer two terminals of the large white resistors, do any read greater than 0.000v DC?

 

[enter]

No Voltage at big wite resistors.

At big output transistors at middle pin i get 6.5 volt, at left i get 1.3volt and the right pin starts with 5volt and after 3 seconds no voltage

The voltage at IC KIA 495AP is 6 volts at pin 12( power supply pin)
Is this ok ?
Link for KIA 495AP
KIA494AP datasheet(1/6 Pages) KEC | BIPOLAR LINEAR INTEGRATED CIRCUIT (VOLTAGE-MODE PWM CONTROLLER IC)

 

[Perry Babin]

The voltage on pin 12 should be approximately the same as the voltage on the B+ terminal.

 

[enter]

B+ terminal is the 12 Volt from power supply?