Telex MCE325 - Manual (Page 40)

4-2 C S I - 2 0 0 U s e r I n s t r u c t i o n s
2 The ribbon connector from the front panel board to the main board is attached at both ends with
locking connectors. To unlock the connector, pull the outer shell away from the circuit board.
Then, pull the ribbon cable out.
Cleaning
Clean the front panel and case with alcohol or a mild solution of detergent and water, and then
wipe off detergent residue with a damp rag. Clean the circuit board (if necessary) with a
tetraflouroethane product such as Flux-Off® CZ by Chemtronics®. Use eye protection and avoid
breathing the vapors with these solvents. Also, avoid getting the solvent in any of the
potentiometers.
Test and Adjustment Procedures
Notes
• All AC voltages are RMS unless otherwise specified.
• All input and output levels were measured using an AC voltmeter calibrated for
1 mW = 0.775V at 600 ohms, but with the 600 ohms in the circuit (0 dBu).
• The following procedures involve changing the MCE325 programming. It may be useful to
note the current positions of all jumpers and DIP switches so that they can be returned to their
proper positions after testing.
• The inside of the top cover contains a location diagram for the programming jumpers and DIP
switches. Place it next to the MCE325 during testing for convenient reference.
• Test procedures are written to be performed in the order presented.
Test Equipment
• Variac
• 15 MHz Oscilloscope
• AC Voltmeter
• Frequency Counter
• DC Voltmeter
• Balanced Audio Generator
• 400 Hz to 30 kHz bandpass filter with +40 dB of gain
Power Supply Test
1 Set a variac to 117 VAC, 60 Hz, and connect the MCE325 to the variac. Observe that each
LED blinks on in sequence, and then all LED’s are off.
2 Measure the voltage across the secondary of T1 (between test points E7 and E8 on the main
circuit board).
V
sec
= 18 ±1.8 VAC
3 Measure the DC voltage across the “+” and “-“ terminals of bridge rectifier CR1.
V
CR1
= 23 ±2.3 VDC