| Electronics > Repair |
| What more i can do? |
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| 222Lab_Test222:
IC16 removed, here are outputs of DO D2 and D5. Its the Non working board. |
| CaptDon:
You could do a million more screen shots of data and address lines but it won't help to zero in on why the unit doesn't work since when it isn't working the busses are unpredictable. You almost need to write a simple loop program and burn it to an eprom and use it to examine what the busses are trying to do. Several hundred posts and it is no closer to working today than it was. Maybe you can find a local 'hands on' technician willing to help you have a look at this unit? This thing is so FUBAR'ed we can never repair it through posts even if we approach 36 pages of posts. You need the help of a good technician with their hands and eyes on the board. |
| asis:
Hi, 222Lab_Test222 Please look at the schematic fragment from .pdf (p.14). - On the back side of the PCB, near the power connector, there are components D1, Q1. If they match the schematic fragment, then there is a high probability that even if you short-circuit the battery to reset the CMOS, this will not be enough. uPD 4990A can still be powered for a long time from the residual voltage from the +5V Bus. You simply do not have enough patience. Try to realize this and reset the CMOS not only by removing the battery and short-circuiting the contacts of the seat, but also by short-circuiting the +5V bus to GND. (You can do this on the chip itself). Naturally, with the equipment disconnected. |
| Harry_22:
Look, all levels are pulled up to +5V. For example a 10k resistor is used for this. Take a similar 10k resistor and connect NL2 rail to ground. Watch the signal (without IC16). It should be around +2.5V. We are looking for other signals on the Data bus if exist. PS If you are tired you can rest. I don't require you to work hard. |
| 222Lab_Test222:
--- Quote from: Harry_22 on December 11, 2024, 08:28:57 pm --- If you are tired you can rest. I don't require you to work hard. --- End quote --- Why you think i am tired. I need to sleep, eat and also give some time to family too. :) |
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