March 21, 1986 HD-1422 Bulletin No: Antenna Noise Bridge HD-1422-1 Schematic Correction - Q101 and Q102 Base Circuit In the base circuit of Q101, R107 [22 kilohm resistor] should connect from the collector of Q101 to the base instead of from the +9 VDC line to the base. At Q102, R108 [10 kilohm resistor] should connect from the collector of Q102 to the base. Make these corrections on your shop schematic for future reference. ------------------------------------------------------------------------------------------------------------------- October 10, 1986 HD-1422 Bulletin No: Antenna Noise Bridge HD-1422-1 Inductive and Capacitive Reactance Readings Reversed In Assembly Manuals [PN 595-3467-00 and -01], the insert drawing of C1 in Pictorial 2-2 shows the tuning capacitor's plates 180 degrees from the correct position [[C1 from the rear shows plates on the right side 0000-1200 location]]. This causes the Reactance knob to be installed 180 degrees from the correct position, resulting in the X[sub L] and X[sub C] readings to be reversed. The correct position for the capacitor plates is shown below in drawing #2 [[C1 from the rear shows plates on the left side 1200-2400 location]]. When the plates are in the position shown in drawing #2, the pointer on ther Reactance knob should be at "0" on the dial. Pictorial 2-2 in Assembly Manual [PN 595-3467-02] is correct. Mark the correction in you shop manuals for future reference. -------------------------------------------------------------------------------------------------------------------- February 6, 1987 HD-1422 Bulletin No: Antenna Noise Bridge HD-1422-3 Weak Output - Can't Get S9 Reading During Adjustments To increase the gain of the Noise Bridge, add a .01 uF capacitor [PN 21-176] in parallel with R109 in the emitter circuit of Q102. -------------------------------------------------------------------------------------------------------------------- July 31, 1987 HD-1422 Bulletin No: Antenna Noise Bridge HD-1422-4 Cabinet Color Change The commincations products are changing from a brown to a black/gray color scheme. Below is a listing of the part numbers for the different color cabinet parts. Description Brown Cabinets Black/Gray Cabinets ---------------- ---------------------- ---------------------------- Cabinet PN 95-1357-1 PN 95-1357-2 Front Panel PN 200-1505-1 PN 200-1505-2 Knob PN 462-1178 PN 462-1236 Heath Parts Replacement is stocking both color parts. -------------------------------------------------------------------------------------------------------------------- August 26, 1988 HD-1422 Bulletin No: Antenna Noise Bridge HD-1422-5 The HD-1422A Antenna Noise Bridge has a chassis that's black and gray. The "A" version model number is screened on the new chassis. Change: From PN 200-1505-2 chassis to a PN 200-1505-3 chassis. The -2 chassis was black and gray, but it wasn't screened with the "A" version model number. Below is a listing of the part numbers for the brown cabinet [HD-1422] and the black/gray cabinet [HD-1422A]. HD-1422 HD-1422a Description Brown Cabinets Black/Gray Cabinets ---------------- ---------------------- ---------------------------- Cabinet PN 90-1357-1 PN 90-1357-2 Front Panel PN 200-1505-1 PN 200-1505-3 Knob PN 462-1178 PN 462-1236 This bulletin supercedes HD-1422-4. ---------------------------------------------------------------------------------------------------------------- Thats everything I hold up to 1989 that covers the HD-1422. Enjoy! ---------------------------------------------------------------------------------------------------------------- 73 de Joe W7LPF/4 [NNN0KUU] QWCA - SOWP - NCVA - FISTS - RCC Gordonsville, Va 22942 [Orange Co]