EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: ddavidebor on October 10, 2013, 03:13:30 pm
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Hi , i've bought a 54xxx oscilloscope, 400mhz, 400ms/s, 2ch.
Now, the screen is dead. It click once or two times at power on.
Anyone has any idea on what problem can it have?
I don't have experience in crt.
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It it's clicking at power up, It sounds like it could be a power supply problem. I'd bet it has nothing to do with the CRT (unless its the HV power supply). Forget about the CRT for now, and troubleshoot it like you would any other circuit.
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Hope not because when the power supply of this things become dead is an apocalypse!
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mmh it was the first thing i've thought about...
but nope, all lines are ok at nominal voltage.
if a power it up, next i shut it down and i power it up again very fast i get this screen for about half a second.
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There are signal and power on the crt cable, but if i touch "autoscale" i can't heard ant relay clicking
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From that image, it looks like a possibility of a deflection or HV supply issue. Have you checked the CRT second anode voltage?
If the supplies are all up but it doesn't respond to buttons, I'd bet it's a failure of the embedded controller. Assuming all of the simple stuff is OK (e.g. CPU clock, reset and power), the most common causes of such a failure are failed memory chips. Can be either EPROMs or RAM. Both are failure prone, while I've noticed that CPU's themselves virtually never fail in embedded systems.
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There seems to be a reset issue. The uP sometimes power up without any signal on data or address. Othertimes if i probe it, it start and look like it's working. It may be a failure in the reset circuit.
Clock is ok, i need to check reset.
Where i need to probe for the second anode voltage?
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Be careful that is a very high voltage.