[Resurrecting a Tek 485] Sweep not from left to right ?


marcosjl31@...
 

Hi guys !

The newbie is back !
Some news : PSU of the 485 delivers proper Low Voltage, I had to adjust the calibrator amplitude (the 5V was out of spec +/- 5mV).

I've been checking (visually) several things :
=> "Ready" indicator does not work.
=> on Chanel 1: leds (x1, x10 are not working), 1MOhm/50ohm selector has no light indication.
=> on chanel 2 : 1MOhm/50ohm selector has no light indication.
Don't know if it's complicated/hard to fix ?

Then, I was watching an interesting video on YouTube (https://www.youtube.com/watch?v=7Qg6ory3L8Y) and suddenly I realize that the sweep on the Tek 485 I've purchased seems to be inverted !

Here is what I get on Channel 2 (1MHz cal signal) : https://drive.google.com/drive/folders/1_9cXIKxCFtC60aFQ6zIm4ujq2paW4tSH

Here is the same signal picture taken from video : https://drive.google.com/drive/folders/1_9cXIKxCFtC60aFQ6zIm4ujq2paW4tSH

To check if I was right to suspect the sweep was not from left to right, I selected GND and turn TIME/DIV to 50ms : the sweep spot on the screen travels from right to left on this 485 !!

Don't think this is correct... but I may be wrong. Could this be due to improper reassembly following a repair?

Hope to here from you,
Jose

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