Help: SB-401

[John Campbell]

Chuck....Before proceeding any further, make sure the carrier balance pot is
truly working correctly,ie. measure from wiper to both ends and make sure
the resistance is varying smoothly with no dropouts. Heath had a chronic
problem with the mounting of these pots which caused many failures. Also, I
suggest checking the circuit discription for the cw circuit and checking
that there is no sidetone leakage into the balanced modulator circuit.
                       73.....John  <<w8jnc>>



>From: Chuck W4MIL <CEMILTON at AOL.COM>
>Reply-To: CEMILTON at AOL.COM
>To: HEATH at LISTSERV.TEMPE.GOV
>Subject: Help:  SB-401
>Date: Mon, 10 Jan 2000 19:58:47 EST
>
>Fellow Heathens--
>
>I have been restoring a very mistreated 401 and finally reached the point
>where alignment is the only thing remaining.  New caps, New tubes, ALL
>crystals installed for stand alone operation, wafer switches cleaned, et.
>al........
>
>The problem I'm having is in the Carrier Null adjustment.  The R and C
>components just won't allow me to balance the thing.  I get good voltage
>readings in the USB position but when switched to LSB, the voltage cannot
>be
>brought to the level achieved in the USB position.  I checked the usual
>components-----no problems.  Front-to-back resistance measurements of the 4
>diodes in the bridge indicate they are o.k. in that they measure about the
>same each.  Tried another LSB crystal and no help.
>
>Anyone got a clue?  Could there be anything in the instructions that may be
>printed incorrectly?  I'm open for suggestions/help.
>
>Thanks in advance es 73 de W4MIL
>
>Chuck
>
>k
>
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