[R-390] Tracking down low sensitivity 0 to 8 mhz problem

[Bob Camp]

HI

This seems to be running on for a while. 

Backing up a bit:

How do you know the sensitivity is low at < 8 MHz? 

I’ve been assuming that you have a signal generator and have checked each of the bands. I’ve also assumed we’re talking about “a bit deaf, but not dead”. If any of that is not correct, then shame on me :).

If this is the case, just how low are you seeing relative to (say) 9 MHz? (are we chasing 6 db or 26 db?)

Is it just as dead at (say) 600 KHz as at 1.5, 2.5 and 5 MHz? (is one of the front end sections getting into the act as well?)

The point being, some of us (ok, maybe just me ….:) )  may be making assumptions that aren’t correct. If we are, our advice isn’t going to be quite as helpful as it could be.

Bob


> On Apr 13, 2024, at 9:58 AM, Jordan Arndt <Outposter30 at shaw.ca> wrote:
> 
> 
> Hi again group...
> 
> While replacing C327 with a mica cap did bring the 1st Xtal Osc output up to snuff, I still find problems below 8Mhz, so I have a few questions for those in the know.
> 
> The service manual states that E402 should show from -4 to -11V when measured with a USM-116 VTVM which has a 100 Megohm input impedance on DC.
> 
> What do you guys use to measure this voltage..?
> 
> What type of tip/connector etc. do you guys use to insert into E402, E209 etc..? Is there a standard "pin" that fits snugly in those connections...? I do have and use the specified CX-1363/U Test Lead, but I cut the alligator clip off the positive lead due to it's size and the tightness of the available space around the test points.
> 
> Lastly, for now at least, Do you all follow the manual instructions for aligning the 1st and 2nd IF, or do you use your own methodology...?
> 
> Thanks for your time and any possible responses...
> 
> 73...Jordan VE6ZT 
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