Heathkit Service Bulletins - SB-110 (Complete)

[Joseph W Lutz]

                        November 3, 1969

SB-110                                          Bulletin No:
Solid State Transceiver                         SB-110-1

                              Audio Oscillation On CW

Problem:        Audio Oscillation in Cw Mode with Sidetone Level
Control full
                on.

Symptoms:       Hand capacity affects near audio output state V6.  The
large
                stand-up 20 ufd electrolytic capacitor C658, when moved,
                appears to have intermittent connection as well as
excessive
                heating of tube V6.

Cause:          B+ applied to VOX amplifier V4B, going through
resistor                network of R49 [3.3 meg], sidetone level control
[500K], and
                R64 [3.3 meg] to grid of audio output amplifier V6B.
This puts
                approximately +3 VDC on grid of V6B causing
instabilityand          excessive plate current flow of this
stage.

Remedy:         Remove resistor R49 [3.3 meg] from receiver IF
circuit board
                [PN 85-115] (See page 147, Fig. 3-2) and replace with a
500 pF
                disc ceramic capacitor [PN 21-13].

Change Notice and marked up Manual will be forwarded to Manual Department
for insert so that future kit production will reflect above changes.
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Thats everything I hold up to 1989 that covers the SB-110.  Enjoy!
-------------------------------------------------------------------------------------------------------------------


73 de Joe  W7LPF/4  [NNN0KUU]
QWCA - SOWP - NCVA - FISTS - RCC
Gordonsville, Va 22942 [Orange Co]

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