s-20r signal genrator hookup

[kc2etm]

Hi i finally aquired a working signal generator and want to align my s-20r the manual says remove cap of 6k8 and connect to this tube when i read voltage from the top of the tube without the cap on im getting voltage does this mean i have to connect it through some type of capacitor or just connect it directly to the top of the tube thanks
fred

[WQ9E]

Fred,

I would get in the habit of always using a DC blocking cap when hooking up a signal generator.  Even places that should have no DC voltage may have it due to a circuit failure. 

You can either find one of the BNC or similar connectors with a built in blocking cap or build your own lead set with a .1 cap in the "hot" lead.

[kc2etm]

ok i did it with a capacitor and its working but my next question is it says set the dial at 2mc well if i connect to the tube as the books states the dial does nothing anyway if i connect to the cap that was on the tube then the dial works so which is it do i connect to the tube top or the removed cap
thanks

[KA8WTK]

You connect to the top of the tube, with the cap off, and inject 455 kc so you can tune the IF transformers on the 455 kc signal for amximum output.
Once that is done, you disconnect the signal generator and replace the cap on the tune. The signal egnerator now connects to the antenna terminals. Now you follow the rest of the directions so you can tune the radio's oscillator, mixer and antenna coils.


Bill

[kc2etm]

Ok thats how i did it and it works much better now
but my question still is why set dial to
2mc i did the if tuneing procedure with it at 2
or all the way to the other end of the scale
with no difference
also on band 4 i have to adjust the oscillator
almost completely out to get close to 34 cant get all
the way to 34 all other bands adjust accuratley
thanks
fred

[KA8WTK]

If I understand your question correctly........
When you inject the 455 kc signal, you are doing this after the stages in the radio that tune the radio to a signal. Moving the dial makes no real difference because when you pulled off the cap from the tube you disconnected the "tuning" part of the receiver.

Bill 

[kc2etm]

That would seem to be how it works but the manual says
set the dial to 2mc so thats how i adjusted but just wondering
is something a typo or im missing something else

[KA8WTK]

I know it says to set it at 2 mc with the bandspread at "0" when doing the 455 kc alingment. I really don't know why the 2 mc is specified for that step. It may be that they use that frequency so there are no images or interference from the radio's oscillator because it is still running.
Anyway, glad you got it working.
Bill

[kc2etm]

Anybody have any ideas about the band 4 problem
on band 4 i have to adjust the oscillator
almost completely out to get close to 34mc cant get all
the way to 34mc all other bands adjust accuratley
thanks

[WQ9E]

You might have the oscillator tracking on the wrong side of the signal on band 4, this is pretty easy to have happen with these low IF frequency single conversion receivers on the higher bands.

Some of the Hallicrafters receivers use low side tracking on the highest range (HFO is 455 below the dial frequency) although high side tracking (HFO operates at the dial frequency plus the IF) is more common.  Check your documentation and see if it specifies the proper relationship for band 4.

The easy way to check for proper tracking side is use an external receiver to pick up the HFO from the S-20R.  Set the S-20R to 20 mhz. and if high side tracking is proper tune your external receiver to 20.455 and with the oscillator trimmer cap set for about half mesh adjust the oscillator coil slug so that you hear the S-20R oscillator in the external receiver.  If it uses low side tracking then the only change is tune the external receiver to 19.545 instead.  Now you can make the end point adjustments and I still prefer using an external receiver for setting the oscillator so that you don't end up tracking on the wrong side.  My Grundig YB-400 gets a lot of use as a test/alignment instrument on the test bench.