Hello to everybody,
I have bought a defective Gould oscilloscope DSO420. At the beginning of the repair the power fuse was blown immediately after inserting the power plug: The RF-filter connector was shorted. Okay, ignore the RF-filter for now.
Some leaked capacitors were within the power supply, all renewed as well as the NiMh accumulator.
Now most of the scope is running:: All LED at the front as well they are switchable and the screen of the scope was lightened th but only a vertical line is shown. No horizontal deflection at all.
The circuit I have attached, all semiconductor are renewed, no change. The electrolytics are renewed, no change. Allways a vertical stroke. Does anyone have an idea?
Regards from Hamburg
Jens
5.3.16 No horizontal deflection
symptoms: The only trace visible is a vertical line at the left hand edge of the screen or the screen is blank. The circuit is described in section 5.4.19, Horizontal deflection and line correction. Check for negative going 20ms sync pulses on the base of Q701 to reset the frame ramp. check that the ramp drive is present by examining the voltage across R717. ensure that all the connections to the horizontal yoke are intact and being driven by U701a.
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Hello zsugori,
thanks for the reply. I know the service manual. Perhaps i forgot to mention, the vertical line is not at the left hand side but in the center of the display. The oscillograms seems to be okay. But I will repeat the measurements. It seems, the circuit itself is working but the sync signal could be the problem.
I will continue!
Regards Jens
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