| Electronics > Repair |
| BK Precision 2120 trace issues |
| << < (17/36) > >> |
| bdunham7:
Yes, and if you eventually replace the resistor, you can just use the long leads to go through the holes and over to the point that the trace used to go to. If there's any danger of touching something else, the small clear teflon tubing can be put over the wires. |
| vexatag:
Bodge installed, not pretty but functional. The horizontal deflection still isn't happening but L801 to D2 is reading at 15.9k ohm (same value as R838 in isolation). What should I test next? |
| bdunham7:
I'm a little worried that the resistor burning up may have been caused by another problem, so don't leave the scope powered on too long at a time. I want you to go back to the step where you used one multimeter as an input to move the dot vertically and then changed to CH2/X to stimulate the horizontal circuit. I had you give me a bunch of voltages measured at the transistors. I didn't explain much, but you should understand what I was looking for to help you go forward here. What I was looking for was both for the signal to change in response to the X input from your DMM--which it did in the appropriate areas--and for the B to E voltage difference to stay at approximately 0.6 volts--which it did. The first thing to look for in transistor troubleshooting is for the base-to-emitter voltage to be something different than about 0.6V, like 0V or over 1V. So you can rerun those tests at some point. But first, lets make sure that there isn't a short somewhere dragging down that D2 line and burning up the resistor. Check the voltages at D1 and D2, then disconnect PG106 (after a power-down, of course) and check them again. If there is a big difference with PG106 disconnected, especially if D2 is near zero when connected but pops up a lot after disconnecting PG106, then stop and turn the scope off. The CRT might be damaged. If there isn't a big change and you have significant positive voltage on D1 and D2 with PG106 connected (say at least 50 volts on each) then you want to start testing at each point both with and without the input from the DMM. Test this way at each point on each component on the schematic going all the way around from L801/802 to Q807--that's L801, R838, Q808, R835, Q807 on the D2 side and you can figure it out for the D1 side. |
| vexatag:
Right-o, D1 connected is 192 V, D1 disconnected is 193 V. D2 connected is 101 V, D2 disconnected is 102 V. I'll test the other points in a bit but wanted to give that little update. |
| vexatag:
Here's the underside of the PCB by the way, I took this just before I soldered the bodge wires in. |
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