HEATHKIT SERVICE BULLETINS - HG/HM/HN/HO

[Joseph W Lutz]

                        FEBRUARY 7, 1973
HG-10B                                          BULLETIN NO:
VFO                                             HG-10B-1

                        HUM ON 40 METERS

REPLACE RFC-1, 28UH [PN 45-18] WITH A 350 UH CHOKE COIL, [PN 45-82].
THIS CHANGE WILL BE PUT INTO PRODUCTION SOON.
------------------------------------------------------------------------------------------------------------------
                        AUGUST 14, 1973
HM-102                                          BULLETIN NO:
WATT METER/SWR BRIDGE                           HM-102-1

            POSSIBLE SHORTS DUETO MOUNTING HARDWARE

THE CIRCUIT BOARD MOUNTING BOLT NEAR R1-[100K] IS EXTREMELY CLOSE TO THE
ADJACENT FOIL.  THERE IS A VERY GOOD POSSIBILITY THIS FOIL COULD BE
ACCIDENTLY GROUNDED.

BY ELIMINATING THE LOCKWASHER AND SUBSTITUTING THE 6-32X1/4" FLAT HEAD
BOLT WITH A 6-32 X 1/4" ROUND HEAD BOLT, [PN 250-31], THE PROBLEM IS
ELIMINATED.
--------------------------------------------------------------------------------------------------------------------
                        DECEMBER 23, 1974
HM-102                                          BULLETIN NO:
WATT METER/SWR BRIDGE                           HM-102-2

                             SERVICE NOTES

PROBLEMS ORIGINATE BECAUSE A 50 OHM LOAD IS NOT USED FOR CALIBRATION;
EVEN THOUGH THE KIT MANUAL SAYS TO USE A 50 OHM LOAD, CUSTOMERS USE
ANTENNAS AND EVEN LIGHT BULBS.  A CLUE THAT THIS IS WHAT IS BEING DONE
WRONG IS AN INABILITY TO NULL DURING SWR ADJUSTMENTS.  ANOTHER CLUE IS
ABNORMALLY HIGH POWER OUTPUT READINGS.

IF A CUSTOMER CANNOT NULL DURING SWR ADJUSTMENT, AND HE IS USING THE
PROPER LOAD, SUGGEST REPLACING THE TOROID COIL AND D-1 THROUGH D-3 WHICH
SEEMS TO BE THE MAGIC CURE-ALL FOR 90% OF ALL THE PROBLEMS ENCOUNTERED
WITH THIS UNIT.

C-4 HAS BEEN SOME PROBLEM, BUT THIS CAPACITOR HAS BEEN CHANGED TO A HUSKY
ONE [PN 31-57].  THE WATT METER PORTION OF THE UNIT WILL NOT ADJUST
PROPERLY UNTIL THE SWR BALANCE HAS BEEN DONE PROPERLY AND A GOOD NULL IS
OBTAINED.  THE INDICATION HERE IS R-6 NOT ADJUSTING PROPERLY.  GAIN, THE
TOROID COIL AND D-1 THROUGH D-3 IS SUSPECT.

SOME CUSTOMERS WILL ASK ABOUT USE OF 75 OHM LINES.  SWR WILL BE HIGHER,
BUT COLLAR READINGS WILL BE WITHIN SPECS.  IT CAN BE RECALIBRATED AND
USED WITH A REASONABLE DEGREE OF ACCURACY.

A COMMON COMPLAINT IS THE HIGH AND LOW POWER READINGS NOT AGREEING.
EXPLAIN TO THE CUSTOMER THE SPECIFICTIONS ON THE METER ACCURACY WHICH IS
PLUS OR MINUS 10% OF FULL SCALE.
--------------------------------------------------------------------------------------------------------------------
                        DECMEMBER 23, 1974
HN-31                                           BULLETIN NO:
DUMMY LOAD                                      HN-31-1

                                            SERVICE NOTES

OVER THE LAST TWO OR THREE YEARS, WE HAVE HAD PROBLEMS WITH RESISTORS IN
THE HN-31 DUMMY LOAD.  THEY ARE NOT SEALED PROPERLY, BECOMING SOAKED IN
OIL AND INCREASING IN VALUE.  EVEN THOUGH THE CUSTOMER IS USING THE
PROPLER LOAD, YOU WILL HAVE CALIBRATION PROBLEMS DUE TO THE CHANGE IN
RESISTANCE.

ALL STORES SHOULD CHECK THEIR HN-31 DUMMY LOADS FROM TIME TO TIME, FOR
PROPER VALUE.
---------------------------------------------------------------------------------------------------------------
                        JANUARY 13, 1975
HO-10                                           BULLETIN NO:
MONITOR SCOPE                                   HO-10-1

                                                        "HOT"
CHASSIS

SOME TRANSFORMERS [PN 54-130] HAVE BEEN FOUND TO BREAK DOWN AFTER ABOUT
FIVE HOURS OF USE.  THE PRIMARY SHORTS TO THE HIGH VOLTAGE SECONDARY,
RAISING THE CHASSIS APPROXIMATELY 1000 V ABOVE THE LINE VOLTAGE.

IF A NEW POWER TRANSFORMER HAS BEEN INSTALLED, BE SURE TO LET THE UNIT
OPERATE FOR A WHILE BEFORE RETURNING IT TO THE CUSTOMER.

THE VENDOR HAS BEEN NOTIFIED, AND CORRECTIONS WILL BE MADE IN REPLACEMENT
STOCK.
--------------------------------------------------------------------------------------------------------------------

73 de JOE
- - - - - - - - - - -W7LPF/4 (NNN0KUU)- - - - - - - - - - - - - - -
QWCA - NCVA - SOWP - FISTS
Gordonsville, Va 22942 (Orange County)
Looking for:  Heathkit HR/HX-20, MR/MT-1,
              Collins 516F-2, 312B-4, EFJ TR Switch
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -