HPPA Amplifier not working

[flacer]

I just finish connecting this amp

But when i switch on the power.. the whole amp not stable.. input voltage oscillating
And the resistor 33ohm(shown in picture) is very hot and turning black..and the voltage drop across this resistor is 15V i think

The input stage current mirror side i am using 9100 ohm
The other adjustable resistor i put in the middle side.

The output voltage is 43V...omg

No shot circuit.... i checked

I did simulate this amp in LTspice.. but in real circuit is not working...

I'm using 45V as main supply

who can help me up?

thanks

[jaycee]

is the 1K trim pot in the BD139 set to full resistance?

Personally I think this circuit is rubbish.

[flacer]

Originally posted by jaycee
is the 1K trim pot in the BD139 set to full resistance?

Personally I think this circuit is rubbish.

I'm using 2k... it is in the middle position... should be 1k

This circuit designed by Bert Molenkamp should be no problem..
I know someone is building this amp before... they are working

Why do you say is rubbish?

regard!
-flacer

[mjf]

hello.
perhaps you have built in a transistor (or diode) reverted or connected wrong?
greetings............

[flacer]

Originally posted by mjf
hello.
perhaps you have built in a transistor (or diode) reverted or connected wrong?
greetings............

Hi~

Previously the BC556 i connected wrong ( i inverse the collector and emitter).. but the circuit nothing burning.. and not working as well

After i check the datasheet and reconnect it... the 33ohms resistor start burning

6 output transistors are fused... and connected follow datasheet


How to know a transistor is faulty? I'm going to check all the transistors



Note: instead BD791 i am using BD139 .... BD792 i am using BD140

-flacer

[mjf]

hello.
bc 556 have max. uce = 60v
you can check these parts with the hfe - tester on a multimeter.i would begin with this................
greetings........

[flacer]

Originally posted by mjf
hello.
bc 556 have max. uce = 60v
you can check these parts with the hfe - tester on a multimeter.i would begin with this................
greetings........

All transistor are ok...

I'm not using the voltage regulator now.. and change the adjustable resistor to 15k ohm

the output voltage now around 23V

the 33 ohm resistor i changed into new one still burning (voltage drop 15V)

next what should i check?

-flacer

[flacer]

wait....

i think the BC556 at current mirror there is burn

i try to change first

-flacer

[flacer]

Just now changed the BC556 at current mirror and 2 X BD139 VAS

the result still same... 33 ohm resistor burning ... but voltage drop across the 33 ohm resistor increased to 20 volt...

i guest the problem is at the VAS...but not sure

any suggestion?

-flacer

[mjf]

only the 556?...........lucky man........now it works.
greetings.................