[R-390] Below 8mhz problem.

Tue, 22 Jan 2002 18:41:06 -0500

Jim,

In order to verify that oscillator V207 is putting out a strong enough
signal to the cathode of V202, do the following:  Connect a DC voltmeter to
test point E209.  Put the Function switch in the STANDBY mode.  You should
read "approximately" -6 VDC, according to TM 11-856A, pp. 111-112.  I just
checked one on the bench, and it reads about -5VDC.  You can check the
output to the 2nd mixer (from the xtal osc deck) and the 3rd mixer (from the
PTO) this same way, but the range of correct readings varies.  See TM
11-865A for more details.

If the voltage is well below -6 VDC, this test won't tell you where the
problem lies (V207, C327, T207, the crystal, etc).  It only tests whether
sufficient signal is getting to the cathode of the 1st mixer.

Walter Wilson - KK4DF
http://www.knology.net/~wewilson
(REAL Radios: R-390A(x5), R-390(x2), Viking II, Ranger, Thunderbolt, KWM-2A)

----- Original Message -----
From: "Jim Temple" <[email protected]>
To: <[email protected]>
Sent: Tuesday, January 22, 2002 5:58 PM
Subject: [R-390] Below 8mhz problem.

>
>  Hello to the group,
>
> I recently bought a "massacre" R-390 and completely tore it down and
cleaned
> and replaced all the "problem" caps.
>
> I have already replaced the 100pF cap at T-207 with no luck.
>
>  The problem I have is that the calibrator is strong and loud on all bands
> 8mhz and above, and below 8mhz is barely audible and extremely faint.
>
>  The receiver will not hear the signal generator at all, so I have not
been
> able to align the variable IF's.
>
>  The fixed IF hears fine, but the signal is injected directly into the IF
> module.  With the variable IF's, the signal can not be heard while input
> into
> the balanced antenna input.
>
>  Perhaps a kind soul has experience with the problem described and will
> offer
> some hints as to a possible fix.
>
>  Thanks.
>
>  Jim Temple
> Louisville, KY.
> 73, KF4ICZ
>
>
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