Clone Goldmund Amplifier

[tommy1000]

Originally Posted by hien.t.nguyen

I think JFET input will hot because
Vc= (33/(56+33)xVcc)-0.6 # 26V,
I2c = 2mA x 2 unit = 4mA
P2c= 112mW => Hot => have DC at output.

DC at output depends on how the feedback loop is designed. Can you show us the feedback loop used in the three models?

[hien.t.nguyen]

Originally Posted by tommy1000

Yes, they have different configurations. The schematics all have revisions so if those revisions ever was used we do not now. The MPSA42/92 are rated at 625 mW so I think it is not a problem.

No,This case is examined in a static mode,dynamic mode is not true because when the bottom NPN on saturated,Vcc of the top PNP is # 2xVcc = 140V

Pc on the NPN : Pc= 4.46mA x 140V = 624mW # Pc max MPSA42/92.
Very easy to fire, explosion

[hien.t.nguyen]

This is Rload line of 2N5565 in 3 cases T5000,M3,M330.

M330 is almost less than linear the 2 cases other.

[thienchay]

I always support you, so sorry that you are not active in the VNAV forums, I don't know anything was done in your problem , but I always support you .
Try to up .
i'm a fan of you .

[tommy1000]

Originally Posted by hien.t.nguyen

No,This case is examined in a static mode,dynamic mode is not true because when the bottom NPN on saturated,Vcc of the top PNP is # 2xVcc = 140V

Pc on the NPN : Pc= 4.46mA x 140V = 624mW # Pc max MPSA42/92.
Very easy to fire, explosion

Can you show where in the schematic this problem can be found?

[hien.t.nguyen]

Originally Posted by thienchay

I always support you, so sorry that you are not active in the VNAV forums, I don't know anything was done in your problem , but I always support you .
Try to up .
i'm a fan of you .

Thank you interested
I have problem not fun in there,I do not want to contribute more posts there.
Well, do not dilute the topic, if you have any questions for technical of Goldmund myclone,you can ask me in here.

Regards,

[hien.t.nguyen]

Originally Posted by tommy1000

Can you show where in the schematic this problem can be found?

Here
Q26=on => Vce(Q26)#0V
Vce(Q29) = 2xVcc = 140V
while the current of Q29 is 4.66mA
=> Pc (Q29) = 624mW

[AndrewT]

How do the load line in post123 fit with the data in the recent posts?
We are discussing BJTs and yet post123 is clearly referring to FETs.
The upper limit of the posted load line graph is 20Vds. How does that relate to the 70Vce and 140Vce that you are stating?

[Walkalone]

Mr. Hien, so sorry for your problem in vnav.
I'm want to ask you few questions. Why in your schematic, between post #25 and schematic in post #100 have a difference? In post #25 gate resistors of power mosfet connect different gate resistors in post #100. What's right?

[tommy1000]

Originally Posted by hien.t.nguyen

Here
Q26=on => Vce(Q26)#0V
Vce(Q29) = 2xVcc = 140V
while the current of Q29 is 4.66mA
=> Pc (Q29) = 624mW

This is not a problem, the FZT957 in your schematic can handle 3000mW
(3W) total power. But only if coold off by the PCB, see picture. You can not replace this part with one MPSA92. (it will get too hot) But the MM9.2 and the chinese clone uses one MPSA92 in this position. That's why goldmund changed to FZT in later models.