Tektronix 2465 CRT Issue

[dietert1]

Here i have an image of the U800 repair i mentioned ten days ago. I mounted the replacement stress-free and added a small heatsink to compensate for a possible loss of heat conduction.

Regards, Dieter

[Nikola Tesla Junior IV]

I may be incorrect, it's late here;

It is my opinion that your readings from those locations (U600 Vertical Output, U800 Horizontal Output) should be verified in depth. I have included some images for you to use as a guide.

Other things that may apply:  GAIN R860/R850;  ASTIG R977; HDC R3401 / R3407; HRZ R801 ------   3100;809;804; Q1851.Q1852,  R615 & others.

[TimeBandit]

Okay, I checked for the waveforms as indicated. Here's what I found.

#56, #57: Very distorted square waves.

#58: Nothing.

#59: Significantly different waveform.

#60, #61: Ok, matches the waveforms shown.

#62: Significantly different waveform.

#63: Nothing.

[MathWizard]

So iirc, the 2465 has a reputation as 1 of the best CRT analog scopes. It has a lot of IC's and stuff ?

What were the best scopes, that were all discrete BJT's/FET's, and maybe a few op-amps ?? When would that have been , the 1950's or 1960's ?

[james_s]

Tek 465 has no custom ICs as far as I know. The 22xx series from the 80s also didn't have these custom ICs. Back in the 50s and 60s scopes were made with vacuum tubes, there were loads of discrete solid state models in the 70s and 80s.

[Kwakerman]

I'd suspect U800 as I had one with similar issue.  Disconnect the deflection plate wires from the tube (the ones going through the PCB hole near U800).  When you switch on you should get a series of vertical spots, one near the top of the screen for the cursor display, 1/2/3 or 4 dots depending on how many channels you have selected that will move up and down with the vertical position controls and another set at the bottom for timebase & gain readouts. If you can see that and the blobs react to focus / intensity / trace position then you know the basics are working and the horizontal deflection (U800) area has a fault.  On my one, one of the U800 outputs for the deflection plates was open circuit so the other output was pulling the beam way off to one side.

[TimeBandit]

I'd suspect U800 as I had one with similar issue.  Disconnect the deflection plate wires from the tube (the ones going through the PCB hole near U800).  When you switch on you should get a series of vertical spots, one near the top of the screen for the cursor display, 1/2/3 or 4 dots depending on how many channels you have selected that will move up and down with the vertical position controls and another set at the bottom for timebase & gain readouts. If you can see that and the blobs react to focus / intensity / trace position then you know the basics are working and the horizontal deflection (U800) area has a fault.  On my one, one of the U800 outputs for the deflection plates was open circuit so the other output was pulling the beam way off to one side.

I did as you suggested and the blobs appeared and reacted pretty much as you described. I'll look into replacing the U800.

[Kwakerman]

This [ebay]154246923795/ebay] may be an option, I used one of the original V1 versions in one of my scopes and it works fine for what I needed that scope to do (general work).  I have another couple of scopes with the correct U800 if I need to do super accurate work.  No experience of the V2 but hopefully it can only be an improvement to the V1 that I am happy with.