Metro JTM45 V3 PI VDC voltages VERY high!

[QuestionMark]

Hi Guys and Gals,

As I've progressed thru my build I am now at the
"all the preamp tubes in place measuring point"
Both V1 & V2 are fine on pins 1,3,6,8 But...
V3 my PI has Very high VDC readings on 1,3,6(8)
300+ on pin 1, 200+ on pin 3(8) and 200+ on pin 6!
As I look at the board and parts I see nothing
unusual. (The only thing I haven't been sure of was
the wiring of the bias pot) I just found a Schematic today
and will look to see what might be out of place there.

Anyone have any idea what might cause such high VDC on V3?
I appreciate your help, thank you.

[big_teee]

pin 1 & 6 are the plates, and they should be +200v plus.
pin 3 and 8 should be tied together and should be around 50v.
If the presence control is not wired properly the voltage will be high on 3 and 8.
Also make sure you used a 470 ohm resistor, tied to pin 3 & 8, and not a 470k, I've seen that before.
T

[big_teee]

On the bias control there are several layouts.
I like the triodestore layouts.
http://site.triodestore.com/JTM45LAYOUT.pdf
I like the 50k pot, it has more range, and will usually work on several different types of power tubes.
Here is another one.
http://ceriatone.com/images/layoutPi...5ceriatone.jpg
Another thing that is good to do is to use the 1 ohm resistors to ground on pin 1 & 8 of the power tubes.
The 1 ohm resistors makes setting the bias much easier.
Both of the diagrams above show the 1 ohm resistors.
Good Luck,
Terry

[QuestionMark]

Hi thanks for the response.

Yes, it's 470 ohm tying 3/8
The presence is correct.

I just measured pin3/8 and I have 160VDC!
not 50 as expected. ???