Tek 2465A Sweep Gets Compressed

[dnowakowski]

I have a relatively low serial number (B011xxx) Tek 2465A. After power has been off for a long time, at power-on the display is normal (left-side of picture).  After a minute or so the horizontal sweep compresses as shown in the right-side of the picture. Pressing the Beam Finder compresses the display even more.  I cleaned the Beam Finder switch, but the problem remains.  Any suggestions as to where to start?

Thank you.

[D2236]

You should look at the service manual wave-form's before and after the horizontal output chip to see if anything changes when started from cold. You will need another working scope to do this.

[squadchannel]

2221A, but I have experience with compression.

In my case, I tested from the output (last transistor) of the horizontal deflection going to the CRT and replacing the second transistor fixed it.

[BlownUpCapacitor]

If you have some freeze spray, try lightly spraying some of the horizontal components to see if they return to normal. From what you have said, this seems to be a textbook case of heat from a unit warming up changing how it operates. Spraying the faulty component with freeze spray will reveal the bad component.

Warning!!!:
Make sure you are pointing a fan at the whole unit all the time whenever operating it without its case! The hybrid chips in 24xx series scopes tend to overheat! Even a fan simply blowing at them is not enough. You will have to be careful not to cook the hybrids.

[tggzzz]

Any suggestions as to where to start?

in

That's not a 2465, it is a 2465A, and there are significant differences. I suggest you change the thread title before you get many irrelevant suggestions.

Start with the service manual.

Check the PSU voltages and ripples preferably before.and after the problem is visible.

Visually inspect the infamous RIFA capacitors before they demonstrate their existence.

Visually check SMD capacitors on the A5 board, if any.

Thereafter you can start the interesting faultfinding.