Heathkit SG-8 Signal Generator

I know it some times is a little thing we forget.

Do you have the user Manual?
Is the modulation set to internal?
I could be way off in my thoughts on this.

In case you don't have a manual here's a link for it.

Click here for manual

The Follower and Attenuator Circuit:
The second triode section of the 12AU7 tube
mounted horizontally on the sub-chassis is
wired as a cathode follower. This provides high
impedance to the oscillator so that changing
loads will have little effect on the oscillator frequency,

and low output impedance so that 50 ohm!

cable can be driven without a lot of loss....

Have you measured the R.F. cable for shorts?

Just to be sure it mentions about a 50 ohm design,
so if you inserted 50 ohm termination it may make a difference. Don't know for sure thought. Just an Idea.

Rod,

Many thanks and will do.

73, Andy N6WVA

I suggest checking the signal voltage at the grid of the cathode follower. (1) The voltages you measure there should be the same at the grid and cathode. (2) If the voltage is also low at the grid side check the cathode follower grid circuit components and if all look good there, then look further back towards the RF oscillator stage. Hope this helps.
73, Rod  WB6FBF

Greetings!

I've been working on getting an old Heathkit SG-8 Signal Generator operational.  I've made good progress in that the AF section works great and as desired, but the RF section only works correctly when I have the RF output in the maximum output level.  At lower levels settings there is no RF output.  Concurrently the grid voltage on the 12AU7 cathode follower is low, but I can't see to determine the reason why.  Tube appears good and most capacitors have been updated.

I'm new to tubes, so any suggestions would be much appreciated.

Andy