RF T3002 ..two burnt ch

[Hexhclass]

Two of the channels are badly burnt.If anyone have the schematics please send it to me ranks33@hotmail.com

 

[brandes.cm]

https://sites.google.com/site/brandescm/home/projects/360a2.pdf?attredirects=0&d=1

It won't be much different than this one.

 

[Hexhclass]

I replace the burnt parts in both ch.now i am getting -27.6 volts on pin 4 of all opamps.Q13 -regulator is getting hot and Q14 is also getting hot.I replace Q13 with a used one but no change.any ideas what can cause that?
Q13
1:23.7v
2:33.5v
3:29.6v

Q114
1:31.5v
2:36.4v
331.9v

 

[brandes.cm]

Pull the regulators and verify the voltage on the op-amps goes away. I would then lift the supply pins on the op-amps and re-install the regulators. Check the voltage on the outputs +-15. If those seem ok, replace the op-amps. I don't believe those parts can take that much supply voltage.

 

[Perry Babin]

Do you mean Q12 and Q13?

Those are the regulators.

 

[Hexhclass]

when i remove the regulators the amp thermal light comes on.

Q13 and Q114 used to get hot.

The amp has no rail voltage now.If i pull the center leg of the rectifires i get rail voltage on the center legs.All outputs are out of the amp right now.I dont no what to check now.Any idea?

 

[Perry Babin]

You've listed, Q13, Q14 and Q114. Are you dealing with 3 difference components or was the Q14/114 a typo? If so, which is correct?

 

[Hexhclass]

yes typo sorry it was Q13 and Q114 but now the amp have more problems like i said in post #6.I dont no where to start looking for the faults.

 

[Perry Babin]

I don't know what to expect if you remove the regulators. Are you referring to Q12 and Q13?

 

[Hexhclass]

yes

 

[Perry Babin]

Reinstall Q12 and Q13.

Remove Q113 and Q114. Does the amp still go into protect?

Do you have any DC across the speaker terminals for either channel?

 

[Hexhclass]

I remove Q113 and Q114.The amp power light is on but i have no rail voltage.If i let the amp idle for a while i get some plusing mv dc on the left ch.All output is still out of the amp.

 

[Hexhclass]

If i pull the center leg of the negative rectifier D13 i get + rail voltage 41v

 

[Perry Babin]

If the power LED is on, the amp has rail voltage. The power LED is driven from the positive rail.

 

[Hexhclass]

befor i pull the center leg of the of the -rectifier the rail voltage was very low 9.3v.I thought that was just some feedback voltage

 

[Perry Babin]

Reinstall the rectifier and post the DC voltage on both LM339s as well as the 494.

 

[Hexhclass]

do i need to reinstall Q113 and Q114 to take the voltage

 

[Perry Babin]

Does the amp act differently with those transistors out of the circuit?

If so, how?

 

[Hexhclass]

If Q114 is in circuit the rail voltage gets lower, Q113 no change.If i pull R124 in the input section while Q114 is out i get 31v +and - rail voltage on some of the outputs
and 12.7v - and + on the opamps

 

[Hexhclass]

I install all outputs and i leave Q114 out of the circuit,with R124 in circuit i get -31v on pin 4 of all opamps so i removed it and now i have - +12.6v on pin 4 and 8.I check for audio.The right ch has good audio and the left is distorted.This amp is giving me a serious beating.