Name: Heathkit HW-101
Brand: Heathkit
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Figure 29. LMO Side Panel (removed)

This is the side panel which has to be removed to repair the LMO. Note the “notches”

on the left-hand side where the “lugs” which hold the LMO on the chassis are attached.

Heathkit Linear Master Oscillators (LMOs) Page 129

Heathkit HW-101 and SB-10X Restoration and Troubleshooting1
Table of Contents3
A)History of the HW-10114
A.1.The SB-Series and HW-Series (Wikipedia)15
A.2.Comparison of Various Models16
A.3.Sb Series Vs HW Series16
A.3.1.Rf Amp and 1St Receiver Mixer17
A.3.2.Sb-101/SB-102 LMO Power Source18
A.3.3.Sideband Bias Circuit18
A.3.4.Accessory Socket18
A.3.5.Cw Filter18
A.3.6.Sb-102 Vs. HW-10119
A.3.7.Power Supply20
B)General Inspection and Restoration Checklist21
B.1.Initial Inspection and Cleaning21
B.2.Resistance and Voltage Checks23
B.3.Receiver Alignment24
B.4.Transmit Alignment24
B.5.Meter Checks24
B.6.Final Checks (Optional)24
C)General Troubleshooting Tips26
C.1.The Unit Appears Completely Dead26
C.2.Does the Unit Receive26
C.2.1.Unit Does Not Receive at All26
C.2.2.Unit Receives on some Bands but Not Others27
C.3.Transmitter Troubleshooting27
D)Transmit Tuning and Operation28
D.1.Initial Transmit Tune-Up28
D.2.Single Sideband Operation29
D.2.1.Ptt Adjustments29
D.2.2.Vox Adjustments29
D.3.Cw Operation30
E)Alignment32
S.2.1.Final Heterodyne Oscillator Alignment38
S.2.2.Driver Neutralization Adjustment38
S.3.Lmo Shifter Adjustment39
T)Uneven Response Across the Band / Bandpass Filter40
To 8895 Khz Bandpass Filter40
T.1.1.Measuring the Bandpass Filter Response (Simple Method)41
T.1.2.Measuring the Bandpass Filter Response (Sweep Analysis)41
U)Signal Level Measurements44
U.1.Receive Signal Levels44
U.1.1.Carrier and Heterodyne Oscillator Levels44
U.1.2.Receive Audio Signal Levels45
Levels)45
V)Using an Audio Signal Generator at 1 Khz, Connect the Generator to the Top of the AF Gain Control and Adjust the AF Gain Control to Provide 500 Mw Audio Output45
V.1.1.Receive RF and if Signal Levels45
V.2.Transmit Signal Levels49
V.2.1.Transmit and VOX Audio Level Troubleshooting Guide49
V.2.2.Transmit RF Signal Levels50
W)Signal to Noise Ratio (SNR)52
W.1.Signal to Noise Ratio (Theory)52
W.1.1.Concept of Signal to Noise Ratio SNR52
W.1.2.Signal to Noise Ratio52
W.1.3.Effect of Bandwidth on SNR53
W.1.4.Signal to Noise Ratio Specifications53
W.2.Measuring Signal to Noise Ratio (SNR)54
W.2.1.Required Equipment54
W.2.2.Test Setup55
W.2.3.Test Methodology55
X)Testing Gain, S+N/N, AGC Threshold and Figure of Merit58
X.1.Testing59
X.1.1.Receiver Gain59
S+N)/N Testing59
X.1.3.Agc Threshold59
X.1.4.Agc Figure of Merit60
X.2.Summation60
Y)Heathkit "S" Meter Circuit61
Y.1."S" Meter Vs. AVC Voltage62
Y.2.Avc and "S" Meter Calibration63
Z)Servicing Procedures64
Z.1.Front Panel Remove and Replace64
Z.1.1.Front Panel Removal64
Z.1.2.Front Panel Installation65
After the Panel Is Installed65
After the Panel Is in Place65
A)During this Procedure, be Especially Careful Not to Place too Much Pressure on the Main Tuning Dial66
B)During this Procedure, be Especially Careful Not to Place too Much Pressure on the Zero Set Shaft66
Z.2.Front Panel Escutcheon Mounting67
Z.3.Sb Series Dial Mechanism69
Z.3.1.Installation of the Spiral Groove Follower Mechanism69
Z.3.2.Installation of Circular Dial on LMO Shaft69
Down. Retighten the Screws70
Drive Arm Base up or Down. Retighten the Screws70
Pointer Is at the "5" Marking. Retighten the Screws71
The Dial Pointer Is at the "5" Marking. Retighten the Screws71
Ab.1.1.Dial Calibration71
Ab.1.2.Re-Engaging the Main Tuning Pulley71
Ab.1.3.Drag When Rotating Main Tuning Knob73
Ab.1.4.Circular Dial Wobble74
Ab.1.5.Spiral Groove Nylon Follower Replacement75
Ab.1.6.Zero Set Dial Mechanism and Pulley76
Ab.1.7.Repairing the Center Hub78
Ab.2.Knob Inlays80
Ab.3.Pa Load Capacitor Remove and Replace81
Ab.4.Function Switch (A.C. Switch)82
Ab.4.1.Finding a Replacement AC Switch82
Ab.4.2.Replacing the AF Gain with a Control Having an AC Switch82
Ab.4.3.Modifying the Failed Switch with a Microswitch82
Ac)Modifications84
Ac.1.Conversion to Low-Z Headphones85
Ac.2.Improved CW Operation86
Ac.3.Transmit Improvements88
Ac.4.Receive Improvements90
Ac.5.Bfo Level to Product Detector90
Ac.6.I.f. Filter Passband Improvements92
Ac.7.Stabilizing Meter Zero Settings94
Ac.8.Antenna Connector96
Ac.8.1.Bnc Connector96
Ac.8.2.So-239 Connector96
Ac.8.3.So-239 to RCA Male Adapter97
Ac.9.Sb-100 CW Filter Modification98
Ac.10.Using an External VFO for Split Frequency Operation100
Ad)Heathkit Filters101
Ad.1. Heathkit Filter Measurements102
Ad.2.Ssb Filter 404-200 Circuit104
Ad.3.Ssb Filter 404-283 Circuit105
Ae)Printed Circuit Boards (Pcbs)107
Ae.1.Modulator Printed Circuit Board 85-127-X109
Ae.1.1.85-127P221 (SB-100, SB-101)109
Ae.2.If Printed Circuit Board 85-128-X110
Ae.3.Bandpass Printed Circuit Board 85-129-X111
Ae.3.1.85-129P223 (SB-100)111
Ae.4.Audio Printed Circuit Board 85-130-X112
Ae.4.1.85-130P224 (SB-100, SB-101)112
Ae.5.Rf Driver Printed Circuit Board 85-131-X113
Ae.6.Crystal Switch Board 85-132-X114
Ae.7.Het Osc, Driver Grid, and Driver Plate Switch Board 85-133-X115
Af)Heathkit Linear Master Oscillators (Lmos)116
Af.1.Lmo Part Numbers & Usage116
Af.1.1.Heathkit TRW LMO117
Af.1.2.Lmo Part Number 110-13118
Af.1.3.Lmo Part Number 110-32119
Af.1.4.Lmo Part Number 110-40120
Af.1.5.Sb-102 LMO (Ver6)121
Af.2.Lmo Repair and Service Notes122
Af.2.1.Lmo Remove and Replace122
Af.2.2.Heath Tube-Type LMO Repair124
Af.2.3.Photos Showing Added Grounding Braid127
Af.2.4.Repairing and Recalibrating a Stuck LMO130
Af.2.5.Heathkit SB-102 Transceiver LMO Stability Fix132
Ag)Matching Heathkit Paint133
Ag.1.1.Matching Heathkit Paint: Part 1133
Ag.1.2.Matching Heathkit Paint: Part 2134
Ag.1.3.Matching Heathkit Paint: Part 3135
Ah)Hw-101 and SB-10X Service Bulletins136
Ah.1.Hw-101 Service Bulletins136
Ah.1.1.Hw-101-1: VFO Drift136
Ah.1.2.Hw-101-2: Repeated Heterodyne Oscillator Tube Failure Inadequate USB-LSB Frequency Shift136
Ah.1.3.Hw-101-3: Carrier Null Control Failure136
Ah.1.4.Hw-101-4: Low Output on 40 Meters136
Ah.1.5.Hw-101-4: Low Output on 40 Meters137
Ah.1.6.Hw-101-5: Alternate Method of Neutralizing the Final Amplifiers137
Ah.1.7.Hw-101-5: Alternate Method of Neutralizing the Final Amplifiers137
Ah.1.8.Hw-101-6: SB & HW Series Audio Preamplifier & VOX Circuit Troubleshooting Guide138
Ah.1.9.Hw-101-7: SB & HW Series Instability & Corrective Information138
Ah.1.10.Hw-101-8: Oscillations or Low Drive138
Ah.1.11.Hw-101-9: Self Oscillations Occurring after Installation of Steel Comb Brackets139
Ah.1.12.Hw-101-10: S-Meter Drift139
Ah.1.13.Hw-101-11: Low Receiver Sensitivity139
Ah.1.14.Hw-101-12: Improperly Manufactured 6HS6 Tubes139
Ah.1.15.Hw-101-13: Germanium Diode Change139
Ah.1.16.Hw-101-14: Improve ALC Adjustment140
Ah.1.17.Hw-101-15: Driver and Mixer Switch Shields will Not Take Solder140
Ah.1.18.Hw-101-16: Side Tone too Loud140
Ah.1.19.Hw-101-17: Transceiver Oscillates in Transmit with the MIC Keyed140
Bands141
Ah.1.21.Hw-101-16: VFO Shift141
Ah.1.22.Hw-101-20: Low Power Output, S-Meter Drift, Etc141
Ah.1.23.Hw-101-21: Distorted Audio, no Carrier Null or Erratic Power Output in Voice Mode141
Ah.1.24.Hw-101-22: Relative Power Meter Pegs on 15 and 10 Meter142
Ah.1.25.Hw-101-23: Relays Remain Energized after Transmit Condition142
Ah.1.26.Hw-101-24: Poor AGC Action142
Ah.1.27.Hw-101-25: 100 Khz Calibrator Spurs142
Ah.1.28.Hw-101-26: Receiver Recovery Slow143
Ah.1.29.Hw-101-27: Erratic VFO Tuning143
Ah.1.30.Hw-101-28: Carrier Nulls with C14 Trimmer Plates Completely Meshed143
Ah.1.31.Hw-101-29: Poor Preselector Tracking143
Ah.1.32.Hw-101-30: Poor Preselector Tracking143
Ah.1.33.Hw-101-30: Loading Capacitor Turns as Plate Capacitor Is Rotated144
Ah.1.34.Hw-101-30: Loading Capacitor Turns as Plate Capacitor Is Rotated144
Ah.1.35.Hw-101-31: Relays Chatter in VOX Mode144
Ah.1.36.Hw-101-32: "Chirping" and Slow Receiver Recovery144
Ah.1.37.Hw-101-33: ALC Meter Reads below Zero145
Ah.1.38.Hw-101-34: S Meter Drift145
Ah.1.39.Hw-101-35: Poor if Sensitivity145
Ah.1.40.Hw-101-36: Receiver Recovery Slow145
Ah.1.41.Hw-101-37: R-940 Shorting to Shield145
Ah.1.42.Hw-101-38: Poor Carrier Suppression145
Ah.1.43.Hw-101-39: Identification of the 6146A Tubes146
Ah.1.44.Hw-101-40: Noise or Static from Speaker When Chassis Tapped Lightly146
Ah.1.45.Hw-101-41: Relay Chatter in any Setting of the VOX Sensitivity Control146
Ah.1.46.Hw-101-42: Unit "Warbles" When Chassis Is Tapped147
Ah.1.47.Hw-101-43: Poor Sensitivity or Grid or Plate Driver Coils will Not Tune147
Ah.1.48.Hw-101-44: no Ground Pin on Tube Sockets at V10 and V11147
Ah.1.49.Hw-101-45: VFO will Not Adjust Properly147
Ah.1.50.Hw-101-46: Low Power Output; Poor VOX Sensitivity147
Ah.1.51.Hw-101-47: Driver Preselector Won't Peak for Full Output at 7.0 MHZ148
Ah.1.52.Hw-101-48: PEC [PN 84-22] no Longer Used148
Ah.1.53.Hw-101-49: Changeover to 6146B Finals148
Ah.1.54.Hw-101-50: R940 Overheats148
Ah.1.55.Hw-101-51: Operation of Mode Switch Trips VOX148
Ah.1.56.Hw-101-52: VFO Stops Working at High End of All Bands149
Ah.1.57.Hw-101-53: Low Transmitter Output; Low Receiver Sensitivity149
Ah.1.58.Hw-101-54: Receiver Audio Troubleshooting Information149
Ah.1.59.Hw-101-55: AVC Decay too Fast; S Meter Drops too Quickly150
Ah.1.60.Hw-101-56: Low Grid Drive on Certain Portions of One or more Bands150
Ah.1.61.Hw-101-57: Relay Chatter in VOX Mode151
Ah.1.62.Hw-101-58: Receiver Oscillations152
Ah.1.63.Hw-101-59: Finals will Not Neutralize; C913 at Maximum Capacity152
Ah.1.64.Hw-101-60: RF Mod in CQ Magazine152
Ah.1.65.Hw-101-61: Parasitic Oscillations153
Ah.1.66.Hw-101-62: Phase Shift Circuit Board Parts List153
Ah.1.67.Hw-101-63: VOX Delay too Short154
Ah.1.68.Hw-101-64: Load Control Squeaks with the HW-101-30 Mod Installed154
Ah.1.69.Hw-101-65: CW Sidetone Inoperative154
Ah.1.70.Hw-101-66: Rotary Switch Detent Change154
Ah.1.71.Hw-101-67: Cannot Zero S Meter with the Meter Zero Control155
Ah.1.72.Hw-101-68: Wiring for Use with the HD-15 Phone Patch155
Ah.1.73.Hw-101-69: no Power Output in USB or LSB; Tune Okay155
Ah.1.74.Hw-101-70: Sidetone Is too Loud155
Ah.1.75.Hw-101-71: the #266-1116 Switch Detent Breaks During Installation156
Ah.1.76.Hw-101-72: VOX Cycling156
Ah.1.77.Hw-101-73: Tone in Audio When Switch to CW; Relay Chatters When Key Is Closed156
Ah.1.78.Hw-101-74: Keys Continuously When Used with the SA-5010 Memory Keyer157
Ah.1.79.Hw-101-75: R940 Overheats157
Ah.1.80.Hw-101-76: Carrier Null Control Installation Change157
Ah.1.81.Hw-101-77: VFO Stops Oscillating at High End of Dial157
Ah.1.82.Hw-101-78: Tune Control Slips158
Ah.1.83.Hw-101-79: Driver Stage Oscillates on 15 Meters158
Ah.1.84.Hw-101-80: Low Transmitter Output Due to Low VFO Output158
Ah.1.85.Hw-101-81: Preselector Capacitors Won't Take Solder159
Ah.1.86.Hw-101-82: S Meter Drifts; if Oscillates159
Ah.1.87.Hw-101-83: Oscillation on 15 Meters159
Ah.1.88.Hw-101-84: R1, R6 and R7 out of Tolerance or Open159
Ah.1.89.Hw-101-85: VOX Activates When Mike Not Connected160
Ah.2.Sb-100 Service Bulletins161
Ah.2.1.Sb-100-1: Diode Leakage in the SB-100, SB-101, HW-100161
Ah.2.2.Sb-100-2: Alternate Method of Neutralizing the Final Amplifiers161
Ah.2.3.Sb-100-3: SB & HW Series Audio Preamplifier & VOX Circuit Trouble Shooting Guide162
Ah.2.4.Sb-100-4: SB & HW Series Instability and Corrective Information163
Ah.2.5.Sb-100-5: Oscillations or Low Drive165
Ah.2.6.Sb-100-6: Self Oscillations Occurring after Installation of Steel Comb Brackets165
Ah.2.7.Sb-100-7: S-Meter Drift165
Ah.2.8.Sb-100-8: Transmitter Oscillates in Transmit with the MIC Keyed165
Ah.2.9.Sb-100-9: Tuning Erratic166
Ah.2.10.Sb-100-10: Relays Remain Energized after Transmit Condition166
Ah.3.Sb-101 Service Bulletins167
Ah.3.1.Sb-101-1D: Driver Oscillates on 40 Meters167
Ah.3.2.Sb-101-2D: Switch Action Improvement167
Ah.3.3.Sb-101-3D: Improper Tuning167
Ah.3.4.Sb-101-4D: Improper Tuning on 40Meters167
Ah.3.5.Sb-101-5D: Grounding Problems on Transceivers168
Ah.3.6.Sb-101-1: Meter Zeroing168
Ah.3.7.Sb-101-2: Repeated Heterodyne Oscillator Failure168
Ah.3.8.Sb-101-3: SB & HW Series Audio Amplifier & VOX Circuit Trouble Shooting Guide169
Ah.3.9.Sb-101-4: Diode Leakage in the SB-100, SB-101, HW-101170
Ah.3.10.Sb-101-5: SB & HW Series Instability & Corrective Information170
Ah.3.11.Sb-101-6: Alternate Method of Neutralizing the Final Amplifiers172
Ah.3.12.Sb-101-7: Oscillations or Low Drive173
Ah.3.13.Sb-101-8: Self Oscillations Occurring after Installation of Steel Comb Brackets173
Ah.3.14.Sb-101-9: S-Meter Drift173
Ah.3.15.Sb-101-10: Low Receiver Sensitivity173
Ah.3.16.Sb-101-11: Transceiver Oscillates in Transmit with MIC Keyed174
Ah.3.17.Sb-101-12: Tuning Erratic174
Ah.3.18.Sb-101-13: Relays Remain Energized after Transmit Condition174
Ah.4.Sb-102 Service Bulletins175
Ah.4.1.Sb-102-1: Meter Zeroing175
Ah.4.2.Sb-102-2: Repeated Heterodyne Oscillator Tube Failure175
Ah.4.3.Sb-102-3: Low Grid Drive - Alignment Problems175
Ah.4.4.Sb-102-4: LMO Instability176
Ah.4.5.Sb-102-5: Low 40 Meter Output176
Ah.4.6.Sb-102-6: SB & HW Series Audio Preamplifier & VOX Circuit Trouble Shooting Guide177
Ah.4.7.Sb-102-7: SB & HW Series Instability & Corrective Information178
Ah.4.8.Sb-102-8: Alternate Method of Neutralizing the Final Amplifiers179
Ah.4.9.Sb-102-9: Oscillations or Low Drive180
Ah.4.10.Sb-102-10: Self Oscillations Occurring after Installation of Steel Comb Brackets180
Ah.4.11.Sb-102-14: Relays Remain Energized after Transmit Condition180
Ah.4.12.Sb-102-15: Poor AGC Action181
Ah.4.13.Sb-102-16: 100KHZ Calibrator Spurs181
Ah.4.14.Sb-102-17: Poor Preselector Tracking181
Ah.4.15.Sb-102-18: Carrier Nulls with C14 Trimmer Plates Completely Meshed181
Ah.4.16.Sb-102-19: Relays Chatter in VOX Mode182
Ai)Using an HW-101 as a 100-Watt PA183
Ai.1.The Basic Mod184
Ai.2.The Enhanced Mod185
Ai.3.Adjustment185
Aj)Tube Substitutes187
Ak)Tube Test Data188

Heathkit HW-101 Troubleshooting

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Brand	Heathkit
Model	HW-101
Category	Transceiver
Language	English