Re: Type CA module in a 545


Tom Lee
 

I agree with Jim. It's not the filaments per se. They don't age that way. The resistance is coming from someplace else.

Cheers
Tom

Sent from an iThing; please excuse the terseness and typos

On Jun 21, 2021, at 6:59, "Jim Adney" <jadney@vwtype3.org> wrote:

On Sun, Jun 20, 2021 at 02:32 PM, David Kuhn wrote:

Everything looked the same except the filament resistance. Pin 15 to
ground is supposed to be ~65 ohms. On the good module is ~74 ohms. On
the weak one, it is 100 ohms.

So I guess I am looking at some old/bad tubes.
I'd be surprised if the actual filaments changed resistance that much. Check the pin to pin resistances right on the tubes and then see if there's a high resistance connection somewhere else. Frankly, 74 Ohms sounds much too high for a cold filament. There must be something else in that path.





Join TekScopes@groups.io to automatically receive all group messages.