Tweet
i have been servicing these dynacords for over 3 yrs now. protect clicks in usually when there is problem with either of the power channels or if there is a problem in the low voltage dual power supply ( 19.3v)
1. first and most importantly.. if u are trying to service and replace components or trying to change bias current. use an ac power source with a 40/60 watt incandescent bulb in series with it ( which will help you to avoid further burning of any replaced components )
2. bias current is factory set in about less than 3.5 mV. you can set it anything between 2.5-3.5 mV. Make sure u set it same for both channels.
make a common ground ( dc ground) and put ur multimeter's negative lead on it, then there is test pins for bias current for both channels ( 4 in total.. bias + and bias - .. check the volatge in each pin.. for single channel if bias + is set at 3.1, make sure bias - is also in range of +/- .1-.2 mV of the same .. ie.. if bias + is 3mV, bias - should be 2.8-2.9mV or 3.1-3.2mV.. if u find anything above or below that.. you might have problem with components on power amp section.
3. if you find any burned components on any side.. u have to replace almost all the resistors and transistors on that power sections ( including all flameproof resistors, 3904/3906 , 15003/15004 , and some a92/a42 transistors.
4. if u cant find any , take out the board and put it upside down.. and put the multimetre on diode/continuity mode.. and check the value on ur meter by touching the emiter and base of power trans 15004/03 . all eight of them.. the working value u should expect is 115-118 , if anything is not working .. it will be higher or the metre will show short circuit.
5. the most prossible problem i come with low volatge power section (19.3v dual) is the IN4007 rect.bridge burning.. and it will blow out the 1.6A fuses on that section.and trips protect mode. so check it.
6. and one more simple trick.. u can always check if everything is ok.. by disconnecting the main power to the board( 48.5 dual supply) and keeping only the 19.3v dual supply. and when u turn on, if everything is ok.. it will trigger the relays. and if it is working.. turn of the power, and reconnect the main 48.5 supply wires.. and turn back on the amp.. but make sure that.. u always check it with series bulb, if everything is ok.. u can connnect direct supply.
1. first and most importantly.. if u are trying to service and replace components or trying to change bias current. use an ac power source with a 40/60 watt incandescent bulb in series with it ( which will help you to avoid further burning of any replaced components )
2. bias current is factory set in about less than 3.5 mV. you can set it anything between 2.5-3.5 mV. Make sure u set it same for both channels.
make a common ground ( dc ground) and put ur multimeter's negative lead on it, then there is test pins for bias current for both channels ( 4 in total.. bias + and bias - .. check the volatge in each pin.. for single channel if bias + is set at 3.1, make sure bias - is also in range of +/- .1-.2 mV of the same .. ie.. if bias + is 3mV, bias - should be 2.8-2.9mV or 3.1-3.2mV.. if u find anything above or below that.. you might have problem with components on power amp section.
3. if you find any burned components on any side.. u have to replace almost all the resistors and transistors on that power sections ( including all flameproof resistors, 3904/3906 , 15003/15004 , and some a92/a42 transistors.
4. if u cant find any , take out the board and put it upside down.. and put the multimetre on diode/continuity mode.. and check the value on ur meter by touching the emiter and base of power trans 15004/03 . all eight of them.. the working value u should expect is 115-118 , if anything is not working .. it will be higher or the metre will show short circuit.
5. the most prossible problem i come with low volatge power section (19.3v dual) is the IN4007 rect.bridge burning.. and it will blow out the 1.6A fuses on that section.and trips protect mode. so check it.
6. and one more simple trick.. u can always check if everything is ok.. by disconnecting the main power to the board( 48.5 dual supply) and keeping only the 19.3v dual supply. and when u turn on, if everything is ok.. it will trigger the relays. and if it is working.. turn of the power, and reconnect the main 48.5 supply wires.. and turn back on the amp.. but make sure that.. u always check it with series bulb, if everything is ok.. u can connnect direct supply.
Comment