I got the reply and there is propably something with Us being too low. It is taken from half of Ua = 280V. There is something wrong I think with diode you can see on board. The Ua is made OK but after the diode for Us there is only 115V. I attach the photo.
The diode I think is russian D226
The diode I think is russian D226
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It was the diode... I found out what is D226 and replaced it with 1n4007... voltage back to 420 on screen and works perfectly... I have a set of new tubes then... good 😀
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Hi Guys
Vs sets the range for Vg1, so now that Vs=420V, you will need about -42V on the control grid as a minimum to keep the tubes under control. Before plugging in output tubes, assure that the bias range encompasses this value, and preferably can sweep to about -50 or -60 to assure full control over the tube.
Have fun
Kevin O'Connor
Vs sets the range for Vg1, so now that Vs=420V, you will need about -42V on the control grid as a minimum to keep the tubes under control. Before plugging in output tubes, assure that the bias range encompasses this value, and preferably can sweep to about -50 or -60 to assure full control over the tube.
Have fun
Kevin O'Connor
So everything is set nearly allright. I can adjust it up to -40V with this pot (somehow strange). I will measure mV going from pin 8 with 1R.
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Hi Guys
Modify the bias supply to provide greater negative sweep BEFORE plugging power tubes in.
Otherwise, it is your choice to waste your tubes.
Have fun
Kevin O'Connor
Modify the bias supply to provide greater negative sweep BEFORE plugging power tubes in.
Otherwise, it is your choice to waste your tubes.
Have fun
Kevin O'Connor
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