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Main => Monitor/Video Forum => Topic started by: Onji on October 23, 2021, 06:11:36 pm

Title: Tube swap question. G1 voltages
Post by: Onji on October 23, 2021, 06:11:36 pm

I have a K4903 that came out of a moon patrol. I'm considering swapping the tube out.

My current tube is a:
Model                  Size   B&K Socket   B&K Heater Voltage   B&K G1 Voltage       Sencore Socket   Sencore Heater Voltage   Sencore Bias
19VMCP22           19           23                        6.3                    50                       23                       6.3                            D


I may pick up this one:
Model            Size   B&K Socket   B&K Heater Voltage   B&K G1 Voltage       Sencore Socket   Sencore Heater Voltage   Sencore Bias
A48QAD220X   19          23                        6.3                      70                          23                       6.3                            D

As you can see the G1 voltage is higher than my current one.

After a LOT of reading around, folks seem to think that G1 voltage isnt all that important with tube swaps. Some have swapped to higher AND lower values and they've been ok.

Is that the case?

I just want to be certain.

thanks

Title: Re: Tube swap question. G1 voltages
Post by: buttersoft on October 25, 2021, 06:31:59 am

I... think you're right. I believe the G1 gets compensated when you turn up the G2 Screen pot (normally on the flyback).

Title: Re: Tube swap question. G1 voltages
Post by: Onji on October 26, 2021, 07:35:17 am

Thanks @buttersoft yeah I'm leaning more towards the "it'll be fine" side so far.

Title: Re: Tube swap question. G1 voltages
Post by: buttersoft on October 26, 2021, 07:35:02 pm

Err, it occurs to me that you didn't mention yoke impedances and inductances. Those need to match between the tubes.