| Sympton | Cause | Procedure |
| A) The music is not heard | a) Supply failure | Test with a voltimeter in the input connector. The voltage has to be 10 VDC + 1,5V. |
| | b) Shorted or open 10V line | Localize failure in decoder module. Carry out
a visual inspection for shorts. When the short is located, replace fuses in decoder module. |
| | c) Supply diode SY124 is open | With the test point on the + of the input connec
tor, TL has to be on. On the cathode of the diode TL will be off. Replace diode. |
| | d) There is no CA5 impulse | With the test point on the + of the input connector and on the CA5 pin, TL has to be on when touching one of the playfield contacts. If it does not get on, see failure in decoder module. |
| | e) The loudspeaker coil is cutted | Check for continuity with the ohmeter the two ter minals of the loudspeaker. If there is no continuity replace loudspeaker. |
| | f) Output transistors closed. | With the test point on the cathode of the supply diode, TL will be off. Replace output transistor and, if necessary, fuses in decoder module. |
| B) At maximum volume the music is weakly heard | a) One of the output transistors is open | Put the test point on the emitter of one of the transistors. If TL turns on when there is no music transistor MC 150 is open. If TL is off while there is no music, transistor MC 140 is open. |
| C) Hum is heard in the loud speaker | a) Supply diode SY 124 is open. | Try with another diode connecting it in parallel with the diode in the module. If the hum disappears, replace the diode. |
| | b) Supply is superior to 10V. | See failure in decoder module |
| D)One or some notes do not sound | a) Command impulse fails | See if the command impulse arrives when touching a game contact, by testing with the test point on the pin of the input connector corresponding to the note which is not heard. If TL does not turn on, see failure in decoder module. |
| E) Fading is not heard | a) 4, 7 uF capacitor is open | With the test point on the positive terminal of the capacitor TL has to turn on quickly when giving a command impulse at CA 5. |
