[R-390] R-390A trouble

[Jim Temple]

Hi Roger and list,

OK, here is what I found.  (Narrowing down the sypmtoms).

1.  In AGC position.
    a.  RF gain at 5.  AGC voltage essentially 0.  Little rushing sound.
Receiver apparently stable.
    b.  As RF gain is increased, background/rushing noise slowly increases
to a level that seems normal and strong.  Noise sounds normal and stable.
TO A POINT.
    c.  As RF gain increases toward 9, the AGC voltage abruptly increases
and the audio breaks into the putt, putt/screeching sound.  The AGC voltage
will continue to increase to about 7-8 volts, and the putt, putt/screeching
continues as long as there is AGC voltage.
    d.  The carrier level remains essentially 0, until the putt, putt
begins, then the carrier lever meter shows a smooth increase to 100.

2.  In MGC position.
    a.  Symptoms are the same until the point that the background noise
becomes strong (about 9 on the RF gain), then the receiver abruptly blocks
as if from a strong signal.  The carrier level meter will JUMP to 100.

3.  An observation is that the problem occurrs at the same position of the
RF gain control, whether the function switch is AGC or MGC.  The only
difference is that the receiver putt, putts in AGC and blocks in MGC.  Both
increase the carrier level to 100 (slowly in AGC, abruptly in MGC.

I hope my observations are clear, if not please ask to clarify.  Thanks,
guys.

Jim
73, KF4ICZ

----- Original Message -----
From: "Roger L Ruszkowski" <rlruszkowski@raytheon.com>
To: <r-390@mailman.qth.net>
Sent: Thursday, March 28, 2002 1:09 PM
Subject: Re: [R-390] R-390A trouble


>>
>> Hi Roger and list,
>>
>> OK, I want to fix this receiver. Here goes. Jim 73, KF4ICZ
>
> Jim, your on it now. Roger.
>
> The question please.
>
>
> Does this putt, putt occur when in the MGC function?
>
> If no, then its most likely an IF deck AGC voltage generation problem and
> not the RF deck at all. If yes, then it is not and AGC problem at all and
> we are looking for a bad CAP.
>
> Roger.
>
>
>
>
>
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