Hi, I got an old amp going recently and noticed the plates glowing slightly on the two 6l6gc. Here is a schematic could someone familiar with negative bias please let me know which resistor and value change as a starting point to run the tubes Abit cooler. I biased a pp about 25 years ago and did all the math with 1ohm resistors but would just love some simple advice ( my math not so good).
Also saw the schematic is used for different model and lists 7027a as well. Can these go straight in or do I need to check or change the socket wiring? Thank you for any help.
Also saw the schematic is used for different model and lists 7027a as well. Can these go straight in or do I need to check or change the socket wiring? Thank you for any help.
On the 6L6, pins 1 and 8 are NC, but on the 7027A these pins are redundantly connected to grids 1 and 2.
If nothing is now connected to the tube socket pins 1 and 8, then the 7027A can be used without mods.
If nothing is now connected to the tube socket pins 1 and 8, then the 7027A can be used without mods.
Last edited:
awesome thanks, the amp has pin 1 nc, pin 8 is used for the HT center tap ground and OT ground so it must be just for 6l6.
Last edited:
There would normally be another cap in there, right off the rectifier. What does that give you?
Attachments
You can permanently connect from 1R to 10R in each cathode connection to ground for measuring
the cathode current. Only use the 1R if you have a high quality DVM.
the cathode current. Only use the 1R if you have a high quality DVM.
Pin 8 is cathode/g3 on both 6L6 and 7027.
Pin 1&4 are g2 on the 7027, so connect 1 and 4 together.
Pin 5&6 are g1 on the 7027, so if 6 is nc now, tie it to 5.
That way you can use either 6L6GC or 7027.
You can also leave 1 and 6 nc, if 7027's are consistent in having g1 and g2 connected to two pins. I've never seen one.
7027 has the internal connections, you can use either pin, there is no need to wire the pins together on the socket.
You can stick a 6L6 in a 7027 socket, but if you try a 7027 in a 6L6 socket, you have to make sure they did not use the pins 1 and 6 as tie points for other circuits.
You can stick a 6L6 in a 7027 socket, but if you try a 7027 in a 6L6 socket, you have to make sure they did not use the pins 1 and 6 as tie points for other circuits.