[h00hbt]

Hi all







Im frying my ECC99´s for the third time and can´t figure out what´s the problem. I seam to have 480V at B+, 465V at B++ and 350V at B+++. So Im ha bit to high at B++ and B+++. Could this be the reason for frying my ECC99´s?

Between pin´s 3 and 8 of the ECC99 I have 107V, this should be 130V.
At measuring point 125V (after 1K res from pin 2 of ECC99) I have 108V
KT88´s are biased at 60mV

Could 20V to much on the plates of the ECC99´s fry them?

What can I do? Increase 1K resistor after 480V B+, to what value? what will this do to B+++ then?

Im sorry but I havn´t figured out how to use the PSU-D II, or I would have given this a try.

Anyway, any ideas of what I should be looking for or suggestions of what to do is much appreciated.

Cheers

[JohnR]

Between pin´s 3 and 8 of the ECC99 I have 107V, this should be 130V.
At measuring point 125V (after 1K res from pin 2 of ECC99) I have 108V
KT88´s are biased at 60mV

It looks like you have only a volt or so of bias voltage. Measure directly across pins 2 and 3, and 7 and 8.

What voltage do you have on pin 3 of the 6SN7?

[h00hbt]

It looks like you have only a volt or so of bias voltage. Measure directly across pins 2 and 3, and 7 and 8.

Hi JohnR

I have measured the points:

Tube 1: pin 2 to 3 = 0,4V and pin 7 to 8 = 0,10V
Tube 2: pin 2 to 3 = 0,8V and pin 7 to 8 = 0,02V

These values are not stable, they flucturate up and down 20% (given measurements are peak)

[/quote]
What voltage do you have on pin 3 of the 6SN7?
[/quote]

I have 2,54V on pin 3&6 on the 6SN7 tube.

Thanks for helping.

Cheers

[h00hbt]

Hi JohnR

I measured the plate voltage on the ECC99s.

Tube 1: pin 1 275V, pin 6 320V
Tube 2: pin 1 300V, pin 6 271V

Then I switched the ECC99 tubes possition with each other and the values are oposite. So it seams like one of the tubes is bad.

Still, I would like to get the B++ voltage down from 465V to 445V, how would be the best way to do so without changing the other B+ voltages? Resistor, what value?

Cheers