My Mits RP WS-48613 will not power on and there is no green light on the front panel. The unit has not been used for about a year so I don't know when or why the condition developed. I'm a former e-tech so I figure I can work though some troubleshooting and perhaps the repair with some help.
I began by checking connections, the main fuse, input voltage and a few of the board fuses with everthing intact. These were Ok so I decided to extend the PCB chassis for better visual and access. I did not see any damage so I checked the 2 fuses on the Main pcb and the 8 fuses on the Power pcb and all checked out Ok. I then applied power and checked the voltage test point that I could locate.
Results:
TP-24V = 280mV
TP12VS 12.94V
TP+24V = 21mV
TP17V = 5.1V
TP9VS = 9.1V
TP30VS = 31.1V
TP6VS = 6.0V
TP28-DM = 28.5V
Assuming all voltages should be present with the chassis disconnected then it appears that I have a problem with with the +/-24 & 17 supplies. Using the service manual, I began looking at the components around the IC9A50 Reg and making some comparisons to the IC9A20 Reg. I found some differences so I then compared similar circuits of PC9A50 with PC9A20 and this is what I found.
PC9A50 Leg 1 = 23.5V, 2 = 23.5V, 3 = 34.5V, 4 = 34.1V, 5 = 29mV, 6 = 35V, 7 = 0V, 8 = 31mV
PC9A20 Leg 1 = 33.9V, 2 = 33V, 3 = 24,5V, 4 = 23.6V, 5 = 24.4V, 6 = 23.6V, 7 = 0V, 8 = 0.5V, 9 = 16V, 10 = 16V, 11 = 5.8V, 12 = 15.3 V
Given this, I think my problem is with PC9A50. Based on these findings, would you concur? Could there be some other bad component that has caused this? is there something else I should check?
Thanks in advance, this board is a great resource. I sort of wish I had the blinking green light as there are so many great write-ups on that failure.
john
My TP measurements done in the above post are with the chassis disconnected with the exception of the 120AC input.
For further troubleshooting I connected only the front panel and some of the TP values changed. With the front panel connected the 12VS, 30VS, 6VS and 28-DM voltages all drop to near zero.
I ohm checked the front panel buttons and each of them are good when depressed or static.
I'm still having problems tracking down this problem. Should I be getting correct voltages on each of the TP's when the chassis is disconnected.
john