[ARC5] Visual Alignment - another discovery.

[Kenneth G. Gordon]

Taking Hutch's advice (and my own thoughts), I replaced the 12SR7 tube 
and its diode detector with a soldered-in 1N34A diode, then connected my 
regular o'scope probe to the diode load resistor (R-18 on the BC-454 
schematic).

The 1N34A is simply replacing the internal diode of the 12SR7 tube, which I 
have removed.

The result is shown here:

http://www.w7ekb.com/Personal/BC454/BC454IF-5.jpg

Compare that with this photo:

http://www.w7ekb.com/Personal/BC454/BC454IF-3.jpg

Conditions of the setup of the sweeper, signal generator, o'scope, input to 
the receiver, and all other settings are identical.

The differences are:
 
1) the probes used (Photo 5 standard o'scope probe, Photo 3 Heathkit RF 
probe), 

2) the existence, or not, of the diode detector (Photo 5 WITH 1N34A 
detector, Photo 3 with NO detector), 

3) where the probe is connected (Photo 3 probe connected to that 
connection point on the last IF can to which the detector is normally 
connected, Photo 5 probe connected to the output of the diode detector and 
across the diode load resistor).

It looks to me as though the 12SR7 tube I had been using has some sort of 
very serious problem, possibly an internal element to some other element 
short, possibly the cathode to filament.

I am next going to use the Heathkit probe and will connect it across the diode 
load resistor to see if this elminates the "filled in" trace leaving only the 
outline.

However, the "filled in" trace does include other information that the bare 
outline trace does not. As to whether or not that information is of any real 
value remains to be figured out.

Anyone care to look the photos over and give me their opinions, please? 

Kenneth G. Gordon W7EKB

"Courage is being scared to death but saddling up anyway."--- John   Wayne