First of all, let me say I have no analog electronics background because I used for many years oscilloscopes but only to troubleshoot mainframes, in the 70's, so only "digital" skill! Presently I would like to see some signals in my Arduino/ESP projects.
My Tek 465 is not showing any trace. A dot is present at the leftmost point of the grid and it becomes a vertical line when applying a signal. Setting the scope in X-Y mode, I can successfully notice the horizontal amplifier works fine while, applying a couple of signals I can successfully display Lissajous figures.
So I focused on trigger (wrong?) and I can say that the sweep never starts, even in "Auto" mode. Luckily I have a second scope to try to diagnose this one and I followed the trigger signal when channel 1 is connected to the internal signal generator. Focusing on diagram 5, adjusting the trigger level control, I can see a quite good signal at point 39 and 40 (pin 9 and pin 8 of U640) but I see no signal and 0V at points 41 and 42. No signal at pin 1 of U870.
Should I remove the two tunnel diodes CR650 and CR652 I see a huge signal at points 41 and 42 and also at pin 1 of U870. But, anyway, I have no trace and no pin of U870 shows any sign of life.
That said, at page 3-13, description of U870, I read that pin 3, even if no trigger signal is present on pin 1, after 100mS: "pin 3 steps LO to turn Q864 on which initiates a sweep". Pin 3 IS low: 0.2V. It is totally unclear to me if pin 3 has to turn low "every" 100mS to initiate the sweeps or, once it is low, the sweeps should continue forever.
By the way, I also noticed a ripple of 10mV on all the voltage rails. I already replaced some electrolytics due to 50Hz ripple. Now the ripple is at 100Mhz and looks almost triangular: something I didn't expect to see. May be this is the cause of U870 to fail, if it even is failing? How to investigate where this ripple come from?
I think the 465 Service Manual is of public domain (I downloaded it here:
https://elektrotanya.com/tektronix_4...wnload.html#dl) but I attach the pages I am referring to.
I want to thank in advance who will be so kind to help!