| Electronics > Repair |
| BK Precision 2120 trace issues |
| << < (3/36) > >> |
| vexatag:
To be absolutely sure: hook up when powered off, power on, record the data, power off again, wait a few minutes, carefully relocate the probes, rinse repeat (metaphorically)? |
| bdunham7:
Yes. No rinsing. |
| vexatag:
Alright, measuring from R509 to both the test point and the positive leg of C503 got 170v±1, measuring the AC lines of BD501 got 129v. |
| bdunham7:
Very good. You just might fix this thing yet! If you look at the diagram, you'll see that the only place you can be dropping all that voltage is across either R504 or Q501. This doesn't mean that the problem is one of the two components, but that's where to start. So the last two places I need you to test voltages is between TP+140V and both sides of R504. After you do that, let it sit for a few minutes and then use the ohms mode to check each resistor in the 260V circuit--R503 through R509. In-circuit they could read lower then their spec, but they can't read higher. Also do a diode check both ways on D502. If you are very lucky, you will find that R504 has gone open or high resistance. |
| vexatag:
Some very interesting developments have occurred. Going from either side of R504 to TP104 revealed no current, but that's not the most unusual thing. R503 and R506, R507, R508, and R509 completely failed a continuity check. On R504 I measured 92Ω and on R505 I measured about 500Ω. On D502 I got 0.560, not sure what that means. |
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