#26 pre amp

[merlin el mago]

channel left measurement schematic

 

[stajo]

And R1, 100 k grid leak resistor is there, measures 100 k and goes between grid pin and ground?

 

[merlin el mago]

And R1, 100 k grid leak resistor is there, measures 100 k and goes between grid pin and ground?

I have 100K pot, isn't enough?

 

[stajo]

Put one there and measure between grid pin and ground. Pot Wiper to ground or Grid Pin to ground, doesnt matter.

 

[merlin el mago]

Done, have I to repeat the measurements?

 

[stajo]

Otherwise we we wont know your grid-kathode bias, right?

 

[merlin el mago]

new measurements

 

[stajo]

What happended? Why did anode voltage go up to 175? Whats the value between pin 1 and 3, grid and cathode?

 

[merlin el mago]

Only opened the volume pot to have 100K, grid-cathode 10,90V

 

[stajo]

Aha, so you need a fixed grid-leak. Shall we tru to go down to 150 V on the anode and measure current again then?

 

[merlin el mago]

adjusting B+ to 150V with the volume pot?

 

[stajo]

nonono, with adjusting the last filter R and a proper fixed grid leak resistor to hold grid to ground

 

[merlin el mago]

Wich value for the last filter R, grid leak resistor I have 110k and 12wich one?

 

[stajo]

What is your value now? If 4750 add like 2 k to that. You know the procedure now.

Grid leak is ok any.

 

[merlin el mago]

OK

 

[iko]

Your circuit works fine now. Don't change anything except for the B+, which needs to be lower so that you measure 140-150V on the plate.

 

[merlin el mago]

new measurement with last filter R 6K8

 

[merlin el mago]

Your circuit works fine now. Don't change anything except for the B+, which needs to be lower so that you measure 140-150V on the plate.

Thanks Iko.

 

[stajo]

We are closing up. Try 10 k. My PSUD from yesterday said 16k but I dont know if I had all your data right.

 

[merlin el mago]

OK