ORION 2550 PROFESIONAL C
Service Manual

Chassis Professional 2550 service procedure

Power supply Using PP2, set the value of +VB at the terminals of CP31 (the values for different types of CRT are indicated in the table on the circuit diagram). Activation of service mode 1. Power up the appliance by pressing the on-off switch simultaneously pressing and holding the MENU button of the cabinet controls until the green Led lights up. 2. Release the MENU button at the cabinet and press the stand-by button on the remote control; the appliance will default to programme 1, or to position AV1 if pin 8 of the SCART 1 socket is connect to a +12 V supply. Important: make certain that the test signal needed for adjustment purposes is available either on programme 1 or on the SCART 1 input, as any further selection of sources is not possible when in service mode. 3. The functions accessible in service mode are listed below; they are selected with the P+ and P� buttons of the remote control then adjusted with the Volume ± buttons. It is advisable to note down the initial value of each parameter before making any adjustment, so that it can be restored easily if necessary. In the event of the NVM memories being replaced, it will be necessary to carry out all of the envisaged service mode adjustments, as the replacement memory is supplied NOT pre-programmed and a new initialization is therefore indispensable. WARNING. If a new NVM is installed, service mode will not allow the various parameters to be accessed until the initialization procedure has been completed. WARNING. Tuning is not possible before initialization. Option byte (Op) The correct value for the individual appliance is indicated on the label affixed to the rear of the cabinet alongside the words Option byte. Initialization (INIT) The initialization procedure, which also indicates the µP software version, is activated by pressing the Volume + button and must be run every time the NVM or the µP is replaced. Remember that this operation erases all memorized data. Screen grid voltage (Vg2 align) Having selected the function, press the Volume + button; a luminous horizontal line will appear in the middle of the screen. Set potentiometer G2 of the EHT transformer so that the line is just visible (in a dimly lit room). Now press the Volume � button and wait a few seconds for service mode to be restored. AGC tuner (AG) Applying a signal of 1mV to the aerial input on a UHF channel, adjust so as to give 4 VDC at pin 1 of the tuner. OSD horizontal position (Hor-pos) Adjust the position of the On Screen Display as desired. Use of UHF band only (UHF only) Select UHF only (on) to speed up the channels auto search in areas where there are no VHF transmitters (e.g. United Kingdom). Automatic tuning (Stepdelays / Stepsizes)