Summary of Contents for Kessler Engineering TL-922 Revival (tm)
- Page 1 TL-922 Revival (tm) Kenwood TL-922 Linear Amplifier Hardware Upgrade Kit Installation Manual 400 Linden Avenue Suite 2 Dayton, Ohio 45403 12 June, 2019 Copyright 2012...
- Page 2 Thank-You! At Kessler Engineering, we endeavor to make your ham radio hobby more enjoyable and trust that our products will bring you many years of faithful service. We Thank-You for the confidence that you have placed in us and in our products.
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Page 3: Table Of Contents
Contents 1 Copyright Notice 2 Caution! 2.1 You May Be Killed! ....... . 3 Introduction 3.1 General Description and Purpose . - Page 4 3.8.6 Electrical Checkout ......3.8.7 Electrical Schematics ......4 Service and Warranty Bibliography 5 User Notes...
- Page 5 List of Figures 3.1 TL-922 Revival Upgrade Kit Contents ....(tm) 3.2 Stock Lamps Prior to Removal ......3.3 Panel with Illumination and Status Lamps Removed .
- Page 6 3.21 Amplifier Chassis After Zener Bias Diode Removal ....3.22 PCB Installation Preparation ......3.23 Electronic Bias PCB Installed .
- Page 7 List of Tables 3.1 TL-922 Revival Modification Kit Contents ....(tm) www.KesslerEngineeringLLC.com...
- Page 8 Copyright Notice This installation manual and its content are the copyright of Kessler Engineering, LLC, Beavercreek, Ohio USA, 2012. All rights reserved. Redistribution or reproduction of part or all of the contents in any form for commercial distribution or exploitation is expressly forbidden.
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Page 9: Caution
Caution! You May Be Killed! The Kenwood TL-922 Linear Amplifier contains high voltages!! LETHAL One must be absolutely careful and fully understand the consequences of working on this am- plifier. IF you come into contact with any of these High Voltages – YOU MAY BE KILLED!! PLEASE! –... -
Page 10: Introduction
Depending upon the modifier’s competency, willingness to doc- ument, and overall “neatness”, troubleshooting such an amplifier can become a daunting task. Kessler Engineering LLC has overcome these challenges for you by making the process of upgrading the TL-922 amplifier much more practical, affordable, and serviceable. -
Page 11: Shortcomings In The Stock Tl-922
Shortcomings in the Stock TL-922 TL-922 in its stock configuration has a number of impairments that adversely affect its operation and longevity. Some of these include: 1. Parasitic Oscillation 2. Excessive Filament Voltage 3. High Voltage / High Current PTT Switching 4. -
Page 12: Tl-922 Revival
The kit comes with all circuit boards assembled and tested. Should a fault develop on any of these circuit boards, it may be removed and serviced. If necessary, they may also be returned to Kessler Engineering for repair. The complete modification kit comes with the items listed in Table 3.1 and shown in Figure 3.1. -
Page 13: Tl-922 Revival
Figure 3.1: TL-922 Revival Upgrade Kit Contents (tm) www.KesslerEngineeringLLC.com... -
Page 14: Preparation
Preparation We highly suggest performing these modifications on a fully functional amplifier. If the am- plifier is non-functional, we suggest repairing the damage (if appropriate) before commencing the modifications. Problems due to a defective T/R relay, shorted Zener bias diode, defec- tive bias relay, inoperative meter lamps, etc., may be ignored since these components are removed and discarded during the modification process. - Page 15 • 8mm Socket • 5mm Hex Key (Allen Wrench) • Soldering Iron and Solder • Solder Wick or Solder Sucker • Volt-Ohm Meter • Heat Gun CAUTION! Modification of the TL-922 amplifier requires desoldering and soldering of numerous components and connections, any of which are prone to damage if subjected to excessive heat or physical force.
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Page 16: Led Board Installation
LED Board Installation Synopsis The amplifier’s incandescent lamps will be removed and replaced with a PCB containing six LEDs which provide meter illumination as well as “Standby” and “On-Air” status indica- tions. Installation The stock lamps are held in-place by rubber grommets and electrically connected to a ter- minal strip as shown in Figure 3.2. -
Page 17: Panel With Illumination And Status Lamps Removed
Figure 3.3: Panel with Illumination and Status Lamps Removed • Place plastic insulating washers behind the PCB attachment holes and then attach the LED PCB using the two screws removed previously. The insulating washers MUST be placed between the PCB and the chassis. •... -
Page 18: Led Circuit Board Correctly Installed
Figure 3.4: LED Circuit Board Correctly Installed www.KesslerEngineeringLLC.com... -
Page 19: Step Start Pcb Installation
Step Start PCB Installation Synopsis The rear fan enclosure will be temporarily removed for installation of the Step-Start PCB. The fuse holders will be re-wired to place the Step-Start circuit in series with the AC Mains fuses and the front-panel On-Off switch. Installation •... -
Page 20: Inserting Step-Start Pcb And Routing Wire Leads
• Remove the two Phillips-Head screws holding AC Mains voltage selection black termi- nal strip. • Insert the Step-Start PCB between the terminal strip and chassis. • Route the wires as shown in Figure 3.7. Route the two #14 yellow wires downward past the right-most fuse holder. -
Page 21: Step-Start Pcb And Terminal Strip Orientation
Figure 3.8: Step-Start PCB and Terminal Strip Orientation • Re-install the fan enclosure (Figure 3.5). • Remove both AC Mains fuses and set aside. • Set the amplifier upside down. The stock, unmodified AC mains fuse holders are shown in Figure 3.9. Figure 3.9: Stock Fuse Holder Configuration •... -
Page 22: Step-Start To Fuse Holder Connection
• Solder together the free end of #14 white wire to the other #14 red wire and insulate with Heat-Shrink tubing. • De-solder and remove the white #14 wire emerging from the upper terminal of the right fuse holder. • Solder either one of the #14 yellow wires emanating from the Step-Start PCB to the upper terminal of the right fuse holder. -
Page 23: Qsk T/R Relay Pcb Installation
QSK T/R Relay PCB Installation Synopsis The stock amplifier’s bias relay, T/R relay, and coaxial cables will be removed and discarded. The QSK T/R Relay PCB (with vacuum relay) will then be installed, completing the quiet QSK upgrade. Bias Relay Removal The bias relay is located between the “RF Input”... -
Page 24: After Bias Relay Removal
• Remove (and retain) the two metal screws holding the bias relay. • Remove and discard the bias relay, lifting it upward and slightly forward, cutting each attached wire as necessary. NOTE: The filament transformer “CT” terminal is electrically connected to the filament choke via a “green”... -
Page 25: Qsk T/R Relay Pcb Installed
• Solder the brown wire emanating from the female two-pin connector to the “TH-1” connection on the High-Voltage transformer. NOTE: This brown “TH-1” wire should be routed near the chassis since this makes the final wire harness lash-up much neater. •... -
Page 26: Stock T/R Relay Removal
3.7.1 Stock T/R Relay Removal The stock T/R relay is adjacent to the tuned input section as shown in Figure 3.14, and held in-place by two screws, accessible from the top-side of the amplifier, through the RF Deck. The RF choke shown in Figure 3.14 will be re-used. Figure 3.14: Stock T/R Relay Prior to Removal •... -
Page 27: Amplifier After T/R Relay Removal
At this point, the amplifier should appear as shown in Figure 3.15. Figure 3.15: Amplifier after T/R Relay Removal Two coaxial cables emanate from the QSK T/R Relay PCB. The shorter coaxial cable provides RF drive to the amplifier and must be connected to the amplifier’s tuned input network. -
Page 28: Qsk Pcb To Tuned Input Connections
Figure 3.16: QSK PCB to Tuned Input Connections The remaining coaxial cable provides the RF output signal path from the amplifier’s load network to the QSK T/R Relay PCB. • Solder the longer coaxial cable’s shield to the ground post on the side of the amplifier, near the output band switch. -
Page 29: Qro Output To Coax Connection
Figure 3.17: QRO Output to Coax Connection Figure 3.18: RF Choke to Bandswitch Connection www.KesslerEngineeringLLC.com... -
Page 30: Qsk Pcb To Qro Output Connections
Figure 3.19: QSK PCB to QRO Output Connections www.KesslerEngineeringLLC.com... -
Page 31: Electronic Bias Pcb Installation
Electronic Bias PCB Installation Synopsis The amplifier’s Zener bias diode and heatsink will be removed. The Electronic Bias PCB will be installed and new connections will be made to the filament transformer and the primary control PCB. 3.8.1 Zener Diode and Heatsink Removal The stock Zener diode and its associated heatsink are located adjacent to the filament trans- former as shown in Figure 3.20. -
Page 32: Amplifier Chassis After Zener Bias Diode Removal
• Remove the ground post near the filament transformer. If unable to remove, then snap off the ground post as close as possible to the chassis “ max height). • Remove all wires connected to the Filament Transformer’s 8V and 80V windings. •... -
Page 33: Electronic Bias Pcb Installation
3.8.2 Electronic Bias PCB Installation The Electronic Bias PCB will be installed in the area formerly occupied by the Zener diode and heatsink, and will mount directly to the filament transformer. Refer to Figure 3.22. Figure 3.22: PCB Installation Preparation •... -
Page 34: Electronic Bias Pcb Installed
Figure 3.23: Electronic Bias PCB Installed www.KesslerEngineeringLLC.com... -
Page 35: Electronic Bias Pcb Connections
3.8.3 Electronic Bias PCB Connections See Figure 3.23. The 10-pin connector provides the following (from left to right): • IG – The grid bias control connection. • CT – Filament transformer center-tap. • 80V – Filament transformer 80V output winding. •... -
Page 36: Filament Transformer Electrical Connections
Figure 3.24: Amplifier IG connection 3.8.5 Filament Transformer Electrical Connections The connections to the filament transformer will be completed next. When finished making the electrical connections to the filament transformer, the results should appear as shown in Figure 3.23. The Filament Transformer includes an isolated 8V secondary winding to provide meter illumination current and an isolated 80V secondary winding to provide current necessary to operate the T/R relay. -
Page 37: Standby-Operate Switch Ry+ Connection
RY+ Electrical Connection The RY+ lead connects to the Standby-Operate switch. Refer to Figure 3.25. • Unsolder and remove the wire (typically grey) from the forward terminal of the Standby- Operate switch. This terminal is shown circled in red in Figure 3.25. •... -
Page 38: Rl Cont" To Tx Connection
Figure 3.26: “RL CONT” to TX connection RY- Electrical Connection The RY- provides electrical current to the QSK T/R Relays. This wire is already soldered to the QSK T/R Relay PCB RY- terminal. GND Electrical Connection • Solder the GND lead to the filament transformer E (ground) terminal. The filament transformer and Electronic Bias PCB should appear as shown in Figure 3.23 on page 27. -
Page 39: Electrical Checkout
3.8.6 Electrical Checkout Now that the hardware upgrade steps have been completed, inspect the amplifier very closely and remove any remaining debris and wire remnants, etc. At this point, the amplifier should appear as shown in Figure 3.27. (NOTE: This Figure shows an additional modification to lower the filament voltage, a modification to the grid circuitry, as well as modification to the cathode drive –... - Page 40 Synopsis Checkout of the modified amplifier will be performed in a series of stages. For each of these steps, AC mains electrical power will be applied to the amplifier. However, It is IMPERATIVE that all safety precautions be observed due to the presence of lethal voltages! DO NOT TOUCH ANYTHING within the amplifier while it is plugged into the AC mains or whenever High-Voltage is present, such as from the anode High-Voltage power supply!!! 1.
- Page 41 4. Confirm both meters are illuminated. 5. Confirm operation of the Step-Start Relay (Within 1-2 seconds after switching the amplifier ON, the Step-Start Relay should produce a soft “Click” and the meter illu- mination should noticeably brighten). 6. After approximately 20 Seconds, switch the amplifier “POWER” switch OFF. If the amplifier Step-Start Relay energized properly and the meters illuminated, then bright- ened after the Step-Start interval, proceed with the following test.
- Page 42 If the lamp sequencing works correctly, then proceed with the next test to confirm switching operation of the QSK T/R Relay. For this test, we recommend using an audible continuity tester. 1. Connect one lead of the continuity tester to the center pin of the SO-239 “RF INPUT” jack.
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Page 43: Electronic Bias Zsac Adjustment Jumper
Electronic Bias Adjustment and Checkout This test confirms correct operation of the High Voltage Power Supply and Electronic Bias. voltages will be present within the amplifier during these tests!! LETHAL ALL AMPLIFIER COVERS MUST BE IN-PLACE DURING TEST!! Under normal conditions with a “healthy” set of 3-500Z tubes, the idling current should be approximately 180-200mA when operating with the “MODE”... - Page 44 5. Set the ZSAC control jumper as shown in Figure 3.28. 6. Install the amplifier bottom cover. 7. Ensure the amplifier is switched OFF. 8. Plug the amplifier into the AC mains. The first portion of this test will re-confirm operation of the Step-Start and expected High- Voltage operation.
- Page 45 4. Set the “LINEAR” switch to OPERATE. Confirm illumination of the STBY light. 5. Electrically short the “Open” end of the keying line cable. Confirm ON AIR light illuminated, STBY light extinguished. Observe and note anode idling current (IP) for proper ZSAC level. 6.
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Page 46: Electrical Schematics
3.8.7 Electrical Schematics Figure 3.29: Step-Start Schematic Diagram www.KesslerEngineeringLLC.com... -
Page 47: Step-Start Pcb
Figure 3.30: Step-Start PCB www.KesslerEngineeringLLC.com... -
Page 48: Qsk T/R Relay Schematic Diagram
Figure 3.31: QSK T/R Relay Schematic Diagram Figure 3.32: QSK T/R Relay PCB www.KesslerEngineeringLLC.com... -
Page 49: Led Schematic Diagram
Figure 3.33: LED Schematic Diagram Figure 3.34: LED PCB www.KesslerEngineeringLLC.com... -
Page 50: Electronic Bias Schematic Diagram
Figure 3.35: Electronic Bias Schematic Diagram www.KesslerEngineeringLLC.com... -
Page 51: Electronic Bias Pcb
Figure 3.36: Electronic Bias PCB www.KesslerEngineeringLLC.com... -
Page 52: Service And Warranty
Service and Warranty Warranty Kessler Engineering, LLC. warrants all of our products to be free from defects in material and workmanship under normal use for a period of one year from the date of purchase. During this one-year warranty period, Kessler Engineering will opt to either repair or replace the product. -
Page 53: Bibliography
Bibliography [1] Kenwood Corporation, “Linear Amplifier Model TL-922A Instruction Manual,” B50- 2587-00 (G). [2] Kenwood Corporation, “Service Manual TL-922 Linear Amplifier,” B51-0835-00, April, 1994. [3] Richard L. Measures, “Improving the Heathkit SB-220 Amplifier,” QST, pp. 42, Febru- ary 1989. [4] Richard L. Measures, “Improving Amplifier Parasitic Suppression for Modern Amplifier Tubes,”... -
Page 54: User Notes
User Notes www.KesslerEngineeringLLC.com... -
Page 55: User Notes - Continued
User Notes - Continued www.KesslerEngineeringLLC.com... -
Page 56: User Notes - Continued
User Notes - Continued www.KesslerEngineeringLLC.com... - Page 57 User Notes - Continued www.KesslerEngineeringLLC.com...
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