Bootstrap Resistor Modification - Crown CE-1000A Service Manual

9.4 Bootstrap Resistor Modification

Applicability: CE-1000, CE-2000, UT-1010, UT-2020,
S3 and M-240 amplifiers containing the following main
modules: CPN 102139-5, CPN 102140-5, CPN
102140-6, CPN 102140-8, CPN 102140-9 and CPN
127354-1. This modification is not necessary on This modification is not necessary on This modification is not necessary on This modification is not necessary on
This modification is not necessary on
127451-4 and 127452-4 PWAs. 127451-4 and 127452-4 PWAs.
127451-4 and 127452-4 PWAs. 127451-4 and 127452-4 PWAs. 127451-4 and 127452-4 PWAs.
Diagnosis: Perform this modification on all listed
boards for any amplifiers retained for servicing. This
modification is required to create a voltage-divider
network to divert excess wattage from key main board
components. Check first to verify if a previous modifi-
cation has already been performed by a Crown au-
thorized servicer. Previously installed bootstrap resis-
tor may be located on main board top next to C1 ca-
pacitor (original 0156 procedure), or may be spliced
into the bootstrap supply wire ( Tech Note 0156 REV A
procedure).
Part Description: 1000-Ohm, 5-Watt resistor (CPN
127438-1), Clip (CPN 127439-1)
Procedure:
1. Locate the bootstrap supply wire. This white wire
runs from the bridge rectifier to WP6 on the main board.
Figure 9.4 Boostrap Resistor Assembly
Field Modifications 9-4
CE Series Service Manual
2. Cut bootstrap supply wire approximately 6 inches
(15 cm) from the end connected to the bridge rectifier.
This will be approximately 8 inches (20 cm) from the
end connected to the main board at WP6.
3. Prep resistor. Hook both leads as shown in Figure
1.
4. Strip and prep both cut ends of the bootstrap sup-
ply wire. Slip a 1-inch length of 4-mm shrink tubing
over the cut end of each wire. Slide back to expose
cut end. Hook each wire in preparation for soldering. See
Figure 9.4.
5. Solder each prepared end of the white bootstrap
supply wire to the resistor.
6. Slide shrink tubing over solder joints and set in place
using a heat gun. See Figure 9.5.
7. Slide supplied clip over resistor and mount in am-
plifier on the corner of transformer closest to the power
supply capacitors using existing bolt. See Figure 9.6.
Figure 9.6 Bootstrap Resistor Installed
Figure 9.5 Bootstrap Resistor Installation
Rev. D