Crown 460CSL - Manual (Page 20)

Power Base-1 & 460CSL Amplifier Service Manual
20
Module Information
MODULE HISTORY
Since its introduction in 1986, the PB-1 has gone
through a number of updates and revisions. Over the
course of its history some of these changes have
resulted in upgrading to newer modules. What follows
is a historical breakdown of PB-1 modules. It should
also be noted that the 460CSL was introduced in 1992
and therefor modules obsoleted before that time were
never used in the CSL version.
OUTPUT MODULES:
Q42576-1
Original output module. No longer available.
Q42661-1
Through hole output module. No longer available.
Q42718-9
Output module: 4 resistor small predriver. PB-1 Only.
Last output module for PB-1 for use with TO-220
package driver transistors.
Q42885-6
TO-3P Driver Output module. Not for use in THC units,
not retrofittable into TO-220 driver transistor units.
Q42967-2
THC Output module with TO-3P drivers. Not retrofittable
to any older units. Does not require special main
module for THC ODEP recompensation. Also im-
proved bias stability.
Q43200-7
THC #2 Output Module. Replaces Q42967-2 only.
Electrically identical, but larger screw head plates
prevent shorting which could occur with the first THC
output module.
MAIN MODULES:
Q42552A0
This was the original main board. It offered 2 front end
gain stages and was also used in the PB-1, MT-600/
LX, MT-1200/LX. It did not include ground lift, but did
offer a choice of .775V or 26 dB voltage gain sensitivi-
ties. No longer available.
Q42664-5
Service replacement for Q42552A0 for PB-1. No longer
available.
Q42682-7
Main #2. Upgraded board from Q42552A0 for PB-1.
No longer available.
Q42776-7
Universally usable PC board, finished module used in
MT-600/1200, MA-600/1200, and PB-1. Added third
gain stage and ground lift switch. For use in the PB-1
install two level pots (C 7409-3) and remove R187 and
R287. Can replace all older modules. Use this module
to replace this or any previous module. This module
can also be used to replace the Q42953-2 module put
into production later. Note that if this module is being
used to replace an older module, you may have to
slide the ground lift switch to the left (ground lift
position) and clip off the plastic switch protrusion in
order for the module to properly fit in the unit.
Q42953-2
PB-1 main module to replace Q42776-7. This or the
Q42776-7 module may be used with TO-3P driver
transistor output modules, and with or without Through
Hole Chassis (THC) in this amplifier.
Q43060-5
THC main module built on D 7993-5 circuit board. On
this module the boost circuit has been deleted, the
third position (1.4V) is added to the Sensitivity Switch,
and additional fault circuitry has been added to the
module. Although it is possible to modify any older unit
to accept this module, it is recommended that the
Q42776-7 be used to replace main modules in all older
units, and this module be used only as a replacement
for itself.