04-27-2017, 01:29 PM
Rich, does your scope have a vertical channel output? This is a BNC connector on the back or side which gives a sample of the vertical signal you see on the scope screen.
Its a very good place to connect the counter, because the signal is of relatively constant and reasonable amplitude and you can actually see the signal you are counting.
You can also connect your counter to pin 5 of the 7F8. This is a relatively low impedance point with a reasonable but not excessive level of signal.
I really don't think the 7F8 is at fault here, because you have a good amount of negative voltage on the grid of the osc. That said, it is probably a good idea to get a spare because the 7F8 is run hard in this radio and they tend to wear out quickly. The tubes condition is not too important on AM, but a weak tube may not oscillate at FM freqs.
I am presently working on a 47 -1227, the cousin of your 47-1230 (without the pushbuttons and SW band). My 7F8 was very weak and did not oscillate at all on FM although AM worked fine.
Its a very good place to connect the counter, because the signal is of relatively constant and reasonable amplitude and you can actually see the signal you are counting.
You can also connect your counter to pin 5 of the 7F8. This is a relatively low impedance point with a reasonable but not excessive level of signal.
I really don't think the 7F8 is at fault here, because you have a good amount of negative voltage on the grid of the osc. That said, it is probably a good idea to get a spare because the 7F8 is run hard in this radio and they tend to wear out quickly. The tubes condition is not too important on AM, but a weak tube may not oscillate at FM freqs.
I am presently working on a 47 -1227, the cousin of your 47-1230 (without the pushbuttons and SW band). My 7F8 was very weak and did not oscillate at all on FM although AM worked fine.
