Tek 2465 Horizontal Sweep Issue

[kellymcdonald78]

I'm not sure if what I'm seeing is the hybrid chip failure or not, but for the life of me I can't seem to get a horizontal sweep (entirely possible this is user error). Everything else seems to work, I get a dot on screen, display works fine, I can adjust manually horizontally and vertically and the cursors (both T and V) work. I haven't used this scope in a decade and wanted to rule anything obvious out before I start tearing it apart. I followed the manual details to get a baseline, but no scan

Thanks

[tautech]

Welcome to the forum.

Check it is not set to XY mode.

[kellymcdonald78]

I don't think so. I've got the Sec/Div switch set to 100ms locked

[bdunham7]

I'm not sure if what I'm seeing is the hybrid chip failure or not, but for the life of me I can't seem to get a horizontal sweep (entirely possible this is user error). Everything else seems to work, I get a dot on screen, display works fine, I can adjust manually horizontally and vertically and the cursors (both T and V) work. I haven't used this scope in a decade and wanted to rule anything obvious out before I start tearing it apart. I followed the manual details to get a baseline, but no scan

Can you post a clear photo of the front of the scope as this happens?  We should be able to spot any user errors that way.

[kellymcdonald78]

Here you go. I also ran the self test and it comes back clean

[bdunham7]

I see the problem, it's upside-downish!

It looks like it's not user error.  You can try pushing the mode selector lever down once to change from AUTO LVL to AUTO, changing the timebase and working all the pushbutton switches a few times to see if anything changes.  It probably won't and it looks like there's an issue near the U700 A-Sweep hybrid or its related circuitry.  If the cursors and readouts are working, U800 and a lot of other things are working fine.  Hopefully you have another scope to use in troubleshooting?

[kellymcdonald78]

Whoops lol, didn’t realize they were upside down. Unfortunately it’s my only scope, so may need to figure something else out. Will at least pop it open and see if there is anything obvious and check some voltages

[Orange]

U700 and U900 are the same hybrid, the are used for the sweep circuits. 155-0240-00 or 155-0240-01

You can try to swap them. See if that works.

They almost never fail is my experience, but you never know, it's easy test.

And for sure check the power supply voltages.
 

[kellymcdonald78]

I tried to see if I could get the B-sweep to work, but no luck (but again not sure if that was user error), will try swapping hybrids and see if that helps

[Orange]

There is a good service manual available here https://w140.com/tekwiki/images/8/8b/070-3831-00.pdf
It has a flow chart for diagnosing the sweep circuit on page 283

[factory]

If it's never had a PSU service, check the condition of the capacitors, they leak conductive electrolyte and short circuits of the PSU circuitry can cause damage, to lots of parts all over the scope, the caps in the picture are from a 2465 of similar age to your scope.

Does connecting a signal to the inputs change the trace at all?

David

[kellymcdonald78]

I swapped the hybrids with no change. Power supply voltages test good. I went through the horizontal troubleshooting tips and 1,2,4 and 5 seem to check out (how long should the voltage ramp on pin 18 take? as it takes a few minutes to ramp up and down). Couldn't check step 3. Pin 11 on U800 is showing -5.6V As per the manual I checked voltages on U800. I'll start working through troubleshooting procedure 5 as best I can without a second scope. One thing I noticed, should the TRIG'D LED stay illuminated? I get get it to flash momentarily when switching modes

[kellymcdonald78]

The caps on the A1 board look good, power supply voltages test good, but I'll open it up to check their condition, I don;t believe it's been re-capped, but it was well maintained before I got it. I can get vertical deflection as expected when I hook the probe up to a known DC voltage. Just no sweeps