EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: rodd on December 16, 2020, 01:12:52 pm
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Dear all,
I am working on this 2465BCT for a while.
First I had to recap and fix the A5 board, which I managed to succeed thanks to the help of this forum.
I managed to adjust DAC and run CAL08 to try to have a better display, which was a little jittery.
Since I could not reduce the jitter, I thought it would be a good idea to replace all the electrolytic capacitor in the LPVS since they all have 1991 date codes.
I replaced one by one at a time to avoid errors (C1115 / C1132 for example).
All new caps were bought from Mouser.
when I powered up the scope I could see the error message PUSH A/B TRIGGER once.
After pushing this button the message display vanished, and it is impossible to display any message no matter what is the position of the READOT INTENSITY control.
I noticed also that it is not possible to display the cursors.
To this moment I have checked the following:
1 - A5 +1.36V and -1.25V ==> OK
2 - J119 voltages ===> all on spec. (specially +10.00V)
I think the problem is that the calibration constants are not valid anymore since the power supply voltages have changed.
However it is NOT POSSIBLE to start any calibration routine since I CAN'T READ THE MESSAGE DISPLAY.
How to I proceed?
Thank you in advance,
Roger
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Hi,
After some more testing, I noticed that if I move the REDOUT INTENSITY slowly, I can obtain a bright spot in the display with the coordinates X= 5 div and Y = 6 div
This spot can be transformed in a kind of square by further adjusting this control..
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you have to go back and check all that you did, not the calibration memory. Looks like a short somewhere, maybe a cap instaled reversed. Check the voltage at the pins and see if it matches the silkscreen and the cap polarity.