Simplistic MosFET HV Shunt Regs

[Salas]

Ever been to Greenland?

 

[stajo]

Unfortunately not. As I used to climb mountains for some reason I have been in almost every corner of the world that has mountains high enough. Greenland hasnt, but thats no reason not going there.

 

[buzzforb]

Yes. Inuit language and greek is closely related. "I drink Metaxa" and "I am a professor" means the same thing

Now that is convenient

 

[stajo]

Have you?

 

[JBLman]

That, the near Zener, and the BJT pair.

I have the same problem, replace these pieces and nothing changed. Any thoughts?

 

[merlin el mago]

Have you checked the other KSA1381?

 

[JBLman]

Have you checked the other KSA1381?

Replaced both ksa1381's/ 2sk117gr and Zener.
The ska1381's were replaced with these since I can't find fairchilds:
MJE350G - ON SEMICONDUCTOR - BIPOLAR TRANSISTOR, PNP, -300V | Newark

 

[merlin el mago]

Red LED lits?

 

[JBLman]

Yes

 

[JBLman]

My voltage show 58v output

 

[Salas]

68k resistors OK? Voltage trimmer does something? Is there normal CCS mV indication on T.P. as before?

 

[JBLman]

68k resistors OK? Voltage trimmer does something? Is there normal CCS mV indication on T.P. as before?

R10 shows 68k installed on the board - r9 shows 43.5k installed also, should I pull a leg up and retest? Or replace?
Voltage trimmer was replaced does minimal was tested before install and did work, can adjust mV's set to 393 what I need .19 + .20mA.

 

[Salas]

Do check R9 better.

 

[JBLman]

Will do

 

[JBLman]

67.7k so it's ok

 

[Salas]

What else, the 840 shows what Vgs when powered?

 

[JBLman]

Now hold on just found a small amount of solder on q4 from outside leg to center cleaned it up and going to test

 

[JBLman]

No change, do you think that it got shorted? Also I'm not familiar with how to test the 840 for vg's. Is it fairly simple? With the use of a volt meter?

 

[Salas]

Probe its outer pins with the DVM. Watch out, there is HV near. Steady.

 

[JBLman]

Easy enough!