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

[JMILLER1706 at cfl.rr.com]

Isn't V-506B the AM detector?  If I am reading the schematic right, V-
506B doesn't connect to the RF deck,... I htink it connects to the AF 
deck (it provides audio to the AF deck).

----- Original Message -----
From: "n4buq at knology.net" <n4buq at knology.net>
Date: Tuesday, March 7, 2006 9:12 am
Subject: Re: [R-390] A bit more on my IF deck
To: R-390 at mailman.qth.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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