Hello everyone, I hope you all are doing fine
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It sadly took a little longer than I wanted to post a new update.
![Scared :scared:](https://www.eevblog.com/forum/Smileys/default/scared.gif)
But dont worry, I was not doing nothing! First of all thank you Kleinstein and Per Hansson for the replies related to the Pre-Regulator FET. If it really seems to be a problem, I will switch it out
![Broken! :-BROKE](https://www.eevblog.com/forum/Smileys/default/smiliey_scope_broke.gif)
In the meanwhile I bought a thermal imager that has a little bit more resolution that the Fluke I was using. And I was in the search of an isolating transformator for my measurements.
When I got my hand on both I started measuring with my Scope. I used my 4-CH Hantek with 1GS/s and wasnt pleased with the resolution in roll mode over >10 seconds.
So I tried fixing my LeCroy, which was out of service since I tried to switch from an HDD to an SSD. I reverted all my changes and got it back running.
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)
I will post both the oscillograms of the Hantek and LeCroy scope.
I am still trying to figure out the Pre-Regulator, because it still doesnt seem to operate correctly as far as I can tell.
Lets start with the oscillogramms from the Hantek. In the picture (Ke2002_Pre_Reg_Meas.png) one can see what Channel and Color corresponds to where I measured. All referenced from the Source of the Control FET (Q608 Ke2001 schematic)
Since I dont have a differential probe to seperate my ground I couldnt measure the Control FET out together with the Pre-Regulator FET. Thats why I put 2 oscillogramms together in one picture. The blue signal is the Gate Voltage of the Pre-Regulator FET referenced from its Source.
And now the same measurement with the LeCroy. Since it has a higer sample rate of 2.5GS/s and more memory, I was able to save the 3 Signals and measure out the fourth in one oscillogramm. I even was able to zoom pretty hard into the Gate signal of the Pre-Regulator FET as to be seen in the oscillogramm below. The measurement points are the same and are labeled directly on the LeCroy.
As far as I can see, after a while the Pre-Regulator seems to be getting its 100Hz like signal that Kleinstein mentioned. The problem is, that I really can't see the signal coming from the FET that controls the CONT line. How can that be? Is it working correctly?
If anyone wants me something to be measured out differently, I can do that without a problem now with the isolating transformer
![DMM :-DMM](https://www.eevblog.com/forum/Smileys/default/smiliey_dmm.gif)
For the thermal imaging, one part is getting pretty toasty. It is labelled U108 and is located behind U107 and U109 (-15V and +15V) regulators. The U108 is an +5V regulator, same as the U110, why are there 2 of them? (page 19 Ke 2002 repair manual)
As far as I can tell the the similarities to the Ke2001 end there, since it doesnt have the same part in the same place as the Ke2002. Does anybody know what it supplies voltage to?
The thermal images show its temperature, it gets over 85°C in about 2 minutes.
![Broken! :-BROKE](https://www.eevblog.com/forum/Smileys/default/smiliey_scope_broke.gif)
Thank you all very much and greetings
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