posite extreme, 100 ohms provided insufficient
delay. Therefore, a satisfactory value of
150
ohms
was selected. Note that the time delay and resistance
values were selected using a line voltage of 220
Vac. I
intended to operate this linear only on the higher line
voltage for increased efficiency.
rectifier protection
1. Remove amplifier case, top shield cover, and right-
side shield.
2.
Remove the four rectifier board hold-down
screws.
3.
Make a wiring map of all twelve wires connected
to the rectifier board and identify by color designator
(fig.
I).
4.
Unsolder all twelve wires at the board end, then
remove diodes.
5.
Wick twelve wire pads and all diode holes.
Remove flux.
6.
Drill out all
diode
holes using a No. 47
(2
mm) drill
bit from the pad side of the board (assuming all
boards are the same).
7.
Using a No. 15 (4.5 mm) drill bit, deburr the new
holes from the component side. Do not deburr the
pad side.
8.
Install resistors (470 k Ww) from the pad side, then
install diodes and capacitors (0.01 at 1
kV) from the
component side. Next:
a.
Solder each pad with its three wires.
b.
Clip component pigtails as you go.
c.
Clean board to remove flux.
d.
Ohmmeter check-note highs will be 470 k.
9.
Connect board to SB-220 using the following
sequence:
a.
Solder red wire to hole D.
b.
Solder blue wires at holes
H
and
J.
c.
Mount board using three screws-omit lower
LH.
d.
Solder bare wire at hole
K.
e. Solder black wire at hole
E.
f.
Solder black wires to holes and pads for the
zener. Observe proper polarity.
g.
Solder orange wire to hole
G.
h.
Solder yellow wire to hole
F.
i.
Solder red small wire to hole
A.
j.
Solder black wire (minus filter bank) to hole B.
k.
Solder black wire
(Ip
meter) to hole C.
This completes the rectifier-board wiring. Dress all
wires at right angles away from the board, then
december
1980
67
CI
-
C7
OOIpF. IIV
RI
-
R7 4701. 1/2W
220 VAC
INPUT
AE
----b-+v"-+--,
CRI CR2 CR3 CR4 CR5 CR6 CR7
CR8
CB
-
C14 0 OlpF. IkV
RB
-
Rl4 470k, ll2W
Except as ~ndlcated, declmal CR9
V*IU*I
Of
CBD.EI11IIE.
Bre
In
mlcr0
lands
fuFh
olhem
are
~n
plcolar
ads
(pFh rerlrtanses
are
m
ohms
k
=
1,000
M
=
1.WO.WO
PRIMARIES CRlO
CRI 1
ig
L----
--_-
7~x
cR12
-
CRl3
CR14
100 50
low low
C
fig.
3.
SB-220surge modifications.
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