[ARC5] Command Set R-13B receiver (108 - 135 Mc)

[Kenneth G. Gordon]

On 21 Oct 2019 at 14:39, Waldo Magnuson via ARC5 wrote:

> ?   Hi, I´m still working on my R-13B. All the tubes check ok on my
> Hickok 6000A tube tester. The RF oscillator tunes from 91 to 120 MHz
> which looks good for the 15 MHz IF. The B+ is low (170 volts) from my
> supply but I´m told that should be ok.

Yes. That is fine.

> There seems to be an excessive
> amount of vibration sensitivity, I tap anywhere and get lots of
> harmonies noise.

Yes. That can happen for any of several reasons.

>  What is usually the cause of that?

That usually means that some coil or capacitor is not connected to the circuit correctly or is 
physically damaged. In my experience ( a receiver which had been "converted" to 10 
meters) there were multiple causes. 1) the coils in the coil-box were all loose, 2) the slugs in 
those coils were rattling around loose in the coils, 3) the main tuning capacitor was 
defective: all the unused plates were ringing. 4) the BFO was damaged (but you don't have 
a BFO so that doesn't matter in your case.)

> Still no signal
> through to the output, just "rush" noise.

First, use your signal generator to input a 15 MHz modulated signal into the mixer grid, or, 
through a DC blocking capacitor (0.01 mfd, although value doesn't really matter) to the 
mixer plate. You should get good audio output.

If that works, then you have a problem with the RF stages somewhere. If that does NOT 
work, then you have a problem with either the mixer itself or with the IF stages.

Feed that 15 MHz modulated signal into the grid of the 1st IF. Etc.

When trouble-shooting receivers, I usually begin with the audio stage and work backwards 
to the antenna.

If you get no result from the above, feed an audio signal to the grid of the audio output tube 
(12A6?), then work "backwards" (forwards) from there.

Next, to output of detector, then last IF, etc.

Ken W7EKB