Re: 5116+5D10 intensity problem


Harvey White
 

OK, then what I was looking for was a significantly larger ripple.  What happens, voltage wise, at the very beginning when you turn on power, and then after the trace starts to dim?  Is there a voltage change there?

Naturally, you do need to measure the HV, since that may be a problem.  Lower HV typically means dimmer trace, and depending on how the CRT is done, can make for a larger trace.

However, and you need to check when the trace goes bad, does the waveform at TP12 change?  If not, then the fault lies beyond that in the circuit.  (could likely be in the CRT circuit).  Since this is a 5116, did you mention if the problem exists with another set of plugins?  IF not, then it's looking as if the problem is rather specifically in the 5D10.

Not familiar with the setup, so I'm just working on symptoms.

Harvey

On 2/15/2020 1:15 AM, Yeun-Jung Wu wrote:
Hello Harvey:

Thank you for your suggestion.

I had checked the ripple content of power supply:

+30V: 20mV p-p; should be 3mV or less
-30V: 8mV p-p; should be 3mV or less
+200: 195, 1.5V p-p; should be 3V or less
+5: 8mV; should be 3mV or less

Plus 30V branch had significant larger ripple content, which may attributed to aging filter capacitor.

According the spec. the accelerating voltage was 4.5kV, pin 2 at CRT socket. My pocket DMM can measure voltage up to 1kV. A HV probe is needed.

Maybe I can order a new piece of 10kV/5mA diode first.

With Tek 485 probed at TP 12, I got an interesting picture of the vertical input signal when 5D10 display a standard graticule grid. It was digitally precise!

Best Regards,

Yeun-Jung Wu


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