Table of Contents
Advertisement
bias, you will need to shut the amplifier off and let it cool down
before you resume.
Tools and resources you will need:
• Small flat screwdriver (non-conductive) for adjusting trimpots
• DC voltmeter
• AC power
Procedure
1.
Turn the amplifier's gain controls all the way down. No test
signal is needed.
2.
Plug the amplifier into an appropriate AC source. Turn the
amplifier on.
3.
Channel 1: While measuring the DC voltage across resistor R146,
adjust trimpot R131 to obtain the voltage listed in Table 1.
4.
Channel 2: While measuring the DC voltage across resistor R246,
adjust trimpot R231 to obtain the voltage listed in Table 1.
After setting the bias, calibrate the positive and negative current
limiting; instructions for the procedure follow below.
4.2 Setting positive and negative
current limits
Tools and resources you will need
• Oscilloscope
• 2-ohm resistive load (rated for at least 1200 watts)
• Shorting connector for amplifier output
• Variable AC transformer (e.g., Variac, Powerstat, etc.) rated for
25A (120V) or 12A (230V). Make sure the AC supply is appropri-
ate for the amplifier.
• 1 kHz audio sine wave generator
• Digital multimeter
• Clamp-on digital current meter
(e.g., Fluke 30 Clamp Meter)
• Small flat screwdriver (non-
conductive) for adjusting trimpots
Procedure
1.
Set the audio sine generator to 1
kHz at 1 volt RMS and connect it
to Channel 1's input. Connect a
2-ohm load and the oscilloscope
probe across Channel 1's output.
2.
Turn up Channel 1's gain control
partway. On the oscilloscope you
should see the amplitude of the
sine wave increase accordingly.
3.
Turn the gain control back down
and apply a short circuit across
the output terminals of Channel
1. Clamp a current probe either
RMX Series Technical Service Manual
Table 1: Bias and current limit adjustments
a C
b i l
a r
o i t
s n
h C
n a
e n
1 l
i b
: s a
C D
o v
a t l
e g
c a
o r
s s
h C
n a
e n
2 l
i b
: s a
C D
o v
a t l
e g
c a
o r
s s
u O
p t
t u
u c
e r r
t n
n i
o t
h s
t r o
d e
o l
d a
C A
u c
e r r
t n
w
h
n e
r d
i v i
g n
s
o h
e t r
l d
a o
C
p i l
i p
g n
o v
a t l
e g
n i
o t
2
h o
s m
R (
M
) S
C
p i l
i p
g n
o v
a t l
e g
n i
o t
2
h o
m
( s
e p
) k a
d I
e l
C A
e d
m
n a
* d
a (
a t
m
b
e i
t n
e t
m
e p
i h
h g
r e
w
h
n e
h
) t o
i F *
u g
e r
s s
o h
w
n
a
e r
r o f
2 1
V 0
a
m
i l p
e i f
onto one of the brown wires running to the AC switch or onto
the gray output wire from channel 1's module.
4.
Turn the gain control all the way up. Adjust trimpots R139 and
R140 equally until the current measured falls within the range
shown in Table 1.
5.
Turn the gain control all the way down and remove the short
circuit so the channel drives the 2-ohm load. Turn the gain control
back up until the output clips. The voltage at which the signal
starts to clip should fall within the range shown in Table 1. If the
clipping is asymmetrical, that is, the signal clips on either the
positive or negative side first, adjust R139 to make it symmetrical.
6.
Turn the gain control down. If the amp has begun to warm up
shut it off and let it cool a few minutes before proceeding with
Channel 2.
7.
Repeat steps 1 through 5 for Channel 2. Use trimpots R239 and
R240 to adjust the current limiting in steps 11 and 12.
8.
Turn both channels' gain controls all the way down. Clamp the
ammeter onto one of the amp's AC wires and check the amp's
idle current. If the amplifier is still at about room temperature,
the idle current should match the value shown in Table 1.
A
d
u j
t s
1 R
6 4
1 R
1 3
2 R
6 4
2 R
1 3
h C
n a
l e n
: 1
1 R
9 3
&
1 R
0 4
h C
n a
l e n
: 2
2 R
9 3
&
2 R
0 4
h C
n a
l e n
: 1
1 R
9 3
&
1 R
0 4
* d
h C
n a
l e n
: 2
2 R
9 3
&
2 R
0 4
C
a h
n n
l e
: 1
d A
u j
t s
1 R
9 3
o f
s r
m y
m
e
y r t
C
a h
n n
l e
: 2
d A
u j
t s
2 R
9 3
o f
s r
m y
m
e
y r t
C
a h
n n
l e
: 1
d A
u j
t s
1 R
9 3
o f
s r
m y
m
e
y r t
C
a h
n n
l e
: 2
d A
u j
t s
2 R
9 3
o f
s r
m y
m
e
y r t
a r
u t
; e r
; s r
m
u
i t l
y l p
u c
e r r
t n
y b
0
5 .
r o f
3 2
. V 0
R
M
X
8
0 5
R
M
X
4 1
0 5
R
M
X
. 0
6 1
V
. 0
4 1
V
. 0
. 0
6 1
V
. 0
4 1
V
. 0
4
4 –
5 .
A
4
5 –
A
8
9 –
. 3
5 7
4 –
5 .
A
4
5 .
5 –
5 .
A
5
6 –
2
– 6
9 2
V
3
. 3
– 5
7 3
5 .
V
4
– 4
3
. 6
– 8
1 4
V
4
. 7
– 4
3 5
V
6
. 2
– 2
0
4 .
, A
0
4 .
, A
0
5 .
A
±
0 1
%
±
0 1
%
4 2
0 5
9 0
V
9 0
V
A
5 .
A
9 4
V
9 6
3 .
V
,
±
0 1
%
13
Advertisement
Table of Contents
