Kessler Engineering TL-922 Revival (tm), Installation Manual

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3.4 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. However, other problems such as
defective tubes, bad high-voltage power supply, etc., will not be cured by merely installing
this modification kit and should be resolved first.
The TL-922 Instruction Manual [1] and the TL-922 Service Manual [2] are excellent ref-
erence documents and one should consult them and become very familiar with the electrical
as well as mechanical layout of the amplifier prior to performing any work on the amplifier.
Copies of these manuals are available from various sources on the Internet, quite often as a
cost-free download.
The hardware upgrade kit entails installation of four printed circuit boards (PCB), mak-
ing connections to those circuit boards and soldering to various components within the
amplifier. Before these PCBs can be installed, the amplifier must be partially disassem-
bled (not that daunting), and a number of components and assemblies removed from the
amplifier.
The four circuit boards to be installed are:
•
LED – Front Panel Display and Meter Illumination
•
QSK – T/R Relays
•
Step-Start – AC Mains Current Limiting
•
Electronic Bias – Control of tube Bias, Step-Start, QSK, LED, and Soft-Switching.
3.4.1 Tools Required
•
#2 Phillips Head Screwdriver
•
#2 Right-Angle Drive Phillips Head Screwdriver
•
Wire Cutters
•
Wire Strippers
•
Small Needle-Nose Pliers
•
Small Vise-Grip Pliers
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