[R-390] Filters

[quartz55]

Doug,

Well, I'm pretty sure the AGC problem in the one IF strip is confined to the 
IF since the other IF unit seems to work pretty good AGC wise, but I do 
still need to check the AGC action even on the 'good' IF strip.  I see 
there's a test for AGC action in the book, I just need to go through it. 
But even the good AGC one has the 'gain drift' problem, so I'm not home free 
on that one yet either.  I suppose I should fix the drift problem first and 
then go on to the one with the bad filters and no AGC.

I'll check the AGC action tomorrow and see if I can get a feeling for where 
the gain drift is coming from.  It will start off with 150uV 455KHz into the 
IF module giving -7V on the diode load, then it 'snaps' and then 25-30uV 
will give -7V, then it starts drifting around on the diode load meter 
finally resting back at about 150uV in a half an hour or so.  Since it takes 
so long to do this, it's hard to check.  The 2uF C551 checks out OK on the 
Fluke, if a bit high, but who knows what it's doing during warm up.  I need 
to start checking voltages as it warms up.  This may take a while.  I do 
have some tube extenders.  Other problem is one of the pins on P112 is 
broken, keeps falling off and now I've lost it, I need a new P112 for that 
one unless I can swap the line to the unused pin, but then the IF modules 
are not compatable.

Yes, that AGC stuff is pretty iffy to check since so many things are hooked 
to it.

I hope I'm responding to this group correctly, I notice I can't just 
'reply'.

BTW Tisha, thanks for the link to this group.  I see you are on Lookout Mt, 
but I was thinking of the one at Chatanooga, I've been there for work 
(repeater up there), but it's a different Mt in a different state.