I've been blessed!

[old_tv_nut]

Testing tubes in the CTC-5, using a Realistic model 108.

I'm getting suspicious results on the 12AT7 color demods. The tester table says to use a quite low setting (4) on the "D" dial, which means a low reading for a given amount of current; that is, the tester expects a lot out of these tubes. Anyway, both demods read really low unless I increase the setting (I tried this because one of the types that could substitute requires a higher setting). Also, the reading jumps to a peak value when the button is pushed and them fades to lower values (easier to see if the "D" knob is cranked up).

Any ideas? Something wrong with the tester? A mistake in the settings table? I have tested about half the tubes and the 12AT7s are the first ones to behave this way. Found one dead 5U4 rectifier, otherwise the other tubes behave reasonably.

[ChrisW6ATV]

Originally Posted by old_tv_nut

Testing tubes in the CTC-5, using a Realistic model 108.

I am amazed to see that Radio Shack once made an item like that. Times sure have changed, so much. Even as of the mid-70's when I started going to RS often and bought plenty of their kits and parts, I don't think they had anything close to a tube tester for sale.