On Wed, Apr 25, 2018 at 10:56 am, vaclav_sal wrote:
I would appreciate some assistance to find out why my 464 has this problem.
Now that all these tertiary issues are disposed of (I hope), on to the problem.
First of all let me make some assumptions here -
You know how to use a triggered scope.
You have tried auto trigger, centering, a beam finder if so equipped and none of this resulted in a trace on the screen.
The nature of your question implies you have not worked on alot of scopes. Now,if you turn the horizontal position to the right or left and then turn the vertical position(s) up and down, does a spot appear on the screen ? Sort of "scan" it that way to see if any combination gets you anything on the screen.
If so, that clears the HV circuit. however it still could be blanking, so it is a positive result, but not a negative for anything else.
If you get no spot or trace at any time the first thing to do is to check the HV. This is usually done best at the CRT cathode which is easy to get to at the socket. You'll have to check the manual to see how much voltage should be there and figure out how to measure it if you meter can't, or at the very least find out if it is there.
I you have HV and absolutely nothing on the screen, then check the deflection plate voltages. Those will be connections on the neck of the CRT. The pair on the side should have about the same voltage on them, and the position control should bring them in to very close, do so and leave the control there and check the other pair of plates. they will either be on top or bottom, usually on top, same deal, try to get the voltages close. Within about 3 volts or so should result in at least a spot on the screen somewhere. If not that leaves CRT bias sources or blanking.
This applies to all scopes. Once we get through that I can download the manual. I will wait because even though I have plenty of HD space it is getting hard to find a particular manual because I have so many, all types of test equipment and audio equipment as well, and all mixed up in different directories depending on where I got them. Once I get it I will probably just leave it open minimized for the duration of the thread. I never reboot. (voluntarily anyway)
If you can't measure the HV get the rest of the info anyway and comeon back y'hear !
One more thing - do you have another scope you can use to troubleshoot this one ?
Jeff Urban