Hello guys,
thank you for your responses.
I checked the caps, but there wasn’t something noticeable. Further I checked the supply-voltages, here I haven‘t also noticed something.
Then I continued to check the channels itself. I determine, the flickering signal is only on channel 1. I guess the timewise flickers on channels 2 to 4 are only side effects of the fault. First some notices I made:
- On initliasation only the attenuators of channel 1 are clicking, from channels 2 to 4 there is nothing to hear
- the flickering signal of channel don’t change its amplitude when I change the resolution of the y-direction.
As I currently said I switched the attenuator boards under the metal case directly at the connector from channel 1 & 2 each other. Noticeable at that was, the mistake behaviour remains at channel 1. Next I took a signal generator and applied an low sinus voltage at the normal BNC-connectors at the front. With another oscilloscope I checked the voltages at the red marked IC in the picture. I measured at the two pins, which are connected to this pair of track, which go to the attenuator board unter the metal cover. They marked in orange.
On channel 2 to 4 I measure the externally applied sinus-signal at these pins, so I think they would work in principal. On channel 1 I didn’t measure the signal. So I think there would be a defect, which prevents the signal’s flow through the attenuator board. But this itself is working, resulting from the exchange of channel 1 and 2. But what or which controls the attenuator boards? There are some ICs to find. For same I got data sheets and for some I didn’t find really much information.
But I think it would be good to know what’s these ICs function in principal are.
- Red market IC: Unfortunately, you can't read the designation out of the heat sink. My guess, that it‘s the sample & hold device, be right? Do you maybe know the type of it?
- Green market IC: On its case you find the descriptions: W9418, ADG286D, MM9423-ACE
My guess this would be the A/D-converter.
- Blue market IC: This is indeed the most mystical IC for me. Its description: imp I10412-01; 9404-FTN
I don’t find really much information about that. I only read, it is called as “daculator”. My guess, its in principle the control unit / IC for each channel. Do you maybe have some further information or experience about this IC? Is that IC maybe also a weak point in these
oscilloscopes, esp. when somebody “shoot down” a channel, as he put in a too high voltage or what else? Probably if this IC “controls” the attenuator boards and the attenuator boards themselves work okay so far, then it would be suspected.
And so far, as I see, schematics or something like that are not really available from Tektronix. Or do you maybe know a source for that?
Link to picture:
https://upload.pokefans.net/m143_a3b3rc3j3.pdf