Test Mode - Roland CPM-300 Service Notes

Apr,1999
Fig. 5 SP OUTPUT: 20.0 Vrms, 6 kHz
• • • •
Adjusting voltage during idling
CAUTION: If the temperature of the heat sink is higher than
30°C, wait until the heat sink becomes cool.
1. Setup
INPUTs - - - - - - - - - - - - - No signal
SPEAKERS - - - - - - - - - - Open
MASTER FADERs - - - - - MIN.
The Effect board can be left removed for the purpose of
adjustment because it is not involved in the adjustment.
2. Adjustment
For this measurement, connect a voltmeter (digital voltmeter
is recommended) across the following points.
Using trial-and-error method, adjust VR1 (CH A) and VR7
(CH B) so that the voltage across the test points reaches +5
mVDC±2mV upon power-up.
• • • •
Power amp board
CH A: TP1(+) and R11 lead (TP1 side) (common)
CH B: TP4(+) and R80 lead (TP1 side) (common)
Make the exact adjustment. If a voltage is out of spec, it
causes undesirable effects:
• • • •
A lower idling voltage increases the total harmonic distor-
tion factor.
• • • •
A higher idling voltage causes the transistor to generate
more heat, which in turn increases the temperature of the
heat sink.
• • • •
Circuit description of power amp board
1. Protection circuits
The protection circuit, when activated by the following circuit,
turns off output relays RL1 and RL2, shutting off the outputs.
♦
Thermal protection circuit (for amps)
The thermal sensor R68 activates the protection circuit as it
detects a temperature of 100°C or higher on the heat sink.
The sensor deactivates the circuit when the temperature
drops to 90°C and below.
♦
DC sensing circuit (for speakers)
This circuit monitors the DC components in the output to
SPEAKERS. When a power output contains DC components
of ±5.5 V or higher, the circuit activates the protection circuit.
To check the sensitivity of the circuit, apply a voltage between
+3 V and +3.5 V to the test point of CH A/B shown below,and
a voltage between -3V and -3.5V to CH A/B. The protection
circuit should be triggered.
• • • • Power amp board
CH A test point: TP2 and GND
CH B test point: TP3 and GND
♦
Muting circuit (for speakers)
Triggers the protection circuit for approx. 5 seconds upon
power up to suppress pop noises.
2. PC limit circuit (for amps)
The PC limit circuit reduces the output when overloaded or
the load is to small (below 2Ω).
3. Limiter circuit
Upon detecting clipped waveform from a power amp, the cir-
cuit reduces the maximum level of the input signal to the
power amp: limits the nominal input level range within approx.
+12 dB at 1 kHz.
• • • •
DSP test mode
♦
test items
1. Version identification and LED
2. Volume
3. Switches
4. Diagnosis
EEPROM,DSP
5. Level balance
Upon successful completion of this test, the unit returns to the
normal operation mode.
6. Anti-feedback
This test is performed in the normal operation mode.
Preparation
0. Entering the test mode
Select DIGITAL REVERB, ROOM. Set TIME to MAX and
LEVEL to MIN. While holding down the AUTO SET, turn on
power.
1. Version identification and LED test
Once in the test mode, the AUTO SET LED lights for 2 sec-
onds. Then, the LED blinks to represent the version number in
three digits (1-digit major version and 2-digit minor version).
The on-duration and interval between blinks depend on the
number to be expressed, as shown below.
0 : turns on for 0.5 sec.
1-9 : blinks at a 0.12 sec. interval, the number of blinks is
equivalent of the number to express.
Example: Ver. 1.20 - turns on for 0.5 s, blinks twice and then
turns on for 0.5 s. Then, the test program proceeds
to the test 2.
2. Volume
The AUTO SET LED turns on indicating the initiation of the
test 2.
Set the TIME to MIN and the LEVEL to MAX. The AUTO SET
LED turns off and the program proceeds to the test 3.
3. Switches
Press ECHO and verify the lighting AUTO SET LED. In the
similar way, press the HALL, STAGE and ROOM in that order
and verify the lighting LED upon pressing. The program pro-
ceeds to the test 4.
4. Diagnosis
During the self-diagnostics sequence the AUTO SET LED
lights. While the LED is lighting, any other operation is not
accepted.
4.1. EEPROM
When the test is successful, the program turns pro-
ceeds to the test 4.2.
If the test fails, the program lights the LED 3 times and
won't proceed to the test 4.2.
CPM-300
7