Eros2 Shunt Regulator Voltage Check

[duman]

Hi all,

I'm hoping to confirm my shunt regulator voltages before proceeding with my Eros2 build, since the MJE transistor metal tab voltages are outside the 210-230V target range.   My mains voltage is 115.1V and I used the "greater than 115V and less than 130V" power transformer input wiring.  All LEDs are lit and the 12AU7 tube is glowing when I apply power.

MJE tab side A - 204V
MJE tab side B - 204V
kregA - 1.84V
kregB - 1.82V
bregA - 202V
bregB - 204V
+regA - 202V
+regB - 204V
IA - 266V
IB - 267V
OA - 202V
OB - 206V

Thanks!

[Paul Birkeland]

Can you post some photos of that area of the build?

The shunt regulator test places all of the operating current of the entire circuit through the 12AU7, which makes the Kreg voltages a little lower than they should be.  How low they get is somewhat dependent on the 12AU7 itself, so there may not actually be an issue here. 

[duman]

Thanks very much for the response Paul.

Here are some pictures.  The LM431 installations are a bit sloppy because I originally installed them backwards.  Please let me know if another view would be helpful.

[Paul Birkeland]

It's somewhat likely that you should plan on tossing those 431s.  In my experience when they get damaged, they will tend to semi-short out internally and can show that random 1.8V voltage across the device.  If those have been heated up a bunch, that could be the problem that's at work here.

When dealing with replacing those, a spring loaded solder sucker is pretty useful for removing the solder on the board.  Solder braid is also adequate for this work. 

-PB

[duman]

Thanks again Paul.  Even if they aren't currently a problem, I would have worried about them malfunctioning at some point anyway.  Will these work?: https://www.mouser.com/ProductDetail/ON-Semiconductor-Fairchild/LM431ACZ.

[Paul Birkeland]

That page wouldn't open, but the part number looks good to me.

[duman]

Sorry about that.  If I could trouble you again, just to confirm I'm ordering the right item: https://www.mouser.com/ProductDetail/ON-Semiconductor-Fairchild/TL431ACZ?qs=fAPocZeZcjglv8zBmIF%252BDQ%3D%3D

I really appreciate the prompt responses and hope you're having a nice weekend!

[duman]

Sheesh, this is the one: https://www.mouser.com/ProductDetail/ON-Semiconductor-Fairchild/LM431ACZ?qs=sGAEpiMZZMuBck1X%252B7j9fLGBSWLcpoerO6HkmYcNQsI%3D

[Paul Birkeland]

Yes, that'll do nicely.