Lanzar 4000d

[megael9]

I'm working with this Lanza, it came to me with a broken output coil, but after I repaired the coil I tested the amp, I noticed that it is making a noice, and RA30, RA31, RA32 and RA35 are getting red hot when the volume is increased.
Eny idea?

 

[Perry Babin]

Is CA8 shorted?

Do you have precisely 1/2 of the full carrier amplitude at the junction of LA3 and LA4?

And virtually no visible carrier at the junction of LA4 and CA8?

 

[megael9]

CA8 is not shorted.
how do I check for the carrier at those 2 points?

 

[Perry Babin]

Scope. It should be 1/2 amplitude at the junction of those two inductors compared to the amplitude at the input of LA3.

 

[megael9]

Do I need to input a signal at the rca jacks?

 

[Perry Babin]

There are some class D amps that won't reliably oscillate unless driven with a signal. If you don't see a rail-rail square wave on the output FETs/filter inductors, try driving a signal into the amp. When checking the amplitude of the carrier, you won't need to have any input.

 

[megael9]

Using the scope AUTO SETUP There is no good readable wave at the output fets, with or without input signal.
Only if I setup my scope to 2 vpp and 800ms, then I get a sawtooth wave.
These 2 signals are between the LA3 and LA4 junction and between the LA4 and CA8 junction.
See pictures bellow.

 

[Perry Babin]

You should have a square wave that swings rail-rail at the outputs. One or both inductors may be shorted.

 

[megael9]

Thank Perry for your help. One of the transformers was shortened.
I rewind it, and everything is good now.
Thank you for your help, and I will be donating.