[R-390] A bit more on my IF deck

[n4buq at knology.net]

Okay, I think I'm carrying on a conversation with myself here, but I'll 
continue...

When I pull the main connector from the IF deck, the resistance at Pin 6 of 
V506 goes very close to 500K (what the book says it should be).  If I 
reconnect the IF connector and unplug the RF deck connector, the same 
thing: 500K.  So, I checked the resistance at pin "E" of the RF deck (the 
point where Pin 6 of V506 connects to the RF deck).  I get about 1.8M 
here.  Those two resistances in parallel yeild what I'm seeing at Pin 6 of 
V506 when everything is connected.

I haven't traced it out, but I assume if I'm supposed to be seeing 500K at 
Pin 6 of V506, then the resistance at Pin "E" on the RF deck should be 
nearly infinite.  Any comments on this?

Barry - N4BUQ

> I got the resistors replaced and all seems fine.  I need to do a full IF
> alignment, but it seems to be behaving just a slight bit better.  I'm not
> sure, but I think it doesn't take quite as long for the system to dump the
> charge from SLOW AGC as it did.  Is that perhaps a function of that 2.7M
> resistor?
> 
> I wanted to check the resistances and voltages around where I had worked.
> Everything looks pretty good except for pin 2 of V506.  According to the
> manual, I should have about -0.4V, but I'm getting nothing (HP410B used
> here).  Checking the resistance, the manual states I should be seeing 500K
> in AGC mode and I'm only seeing 400K here.  There are three resistors to 
GND
> from V506, pin 2 and they add up to 500K.  Apparently I have something 
else
> parallel to this that's pulling the resistance down a bit.  It's always
> something.  Any guesses why I don't see -0.4V here?
> 
> Thanks,
> 
> Barry - N4BUQ
> 
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