TEKTRONIX 2465(plz halp!)

[Dynatr0n]

So I saw this thread here: https://www.eevblog.com/forum/repair/another-2465-300mhz-to-repair/

Now mine had exactly the same problem! So I decided to replace the CRT(made in '83 which was given a crooked picture and got damaged), the high voltage board....and then the main board.

But when I put it all back together, not only is the CRT black, but the panel LEDs won't turn on! Before I replaced the main board, the panel leds would turn on but the CRT would not. Now I checked all the capacitors on the low voltage/power supply board and they display the proper readings. I also notice that when I take current readings with my multimeter on the the pins that attack the power ribbon harness to the main board the readings are exceedingly low(even though the voltage readings are what they should be).

When I turn on the machine, there is the clicking of the relays and the fan turns on, but the screen and the front panel lights don't. So it makes me wonder if there is a firmware problem or if there is insufficient power flowing through the main board to the CRT high voltage board. The front panel unit gets its electricity from the digital control board, which makes me wonder if there is a logic error and the control computer is preventing full power up.

Thoughts?

[med6753]

Go back and check ALL your interconnects. It is very easy to plug the ribbon cables one pin askew or even mix them up. Ask me how I know. And if your 2465 has options such as the Buffer Board make sure the top plate is correctly installed and the long pins on that top plate properly engage the sockets on the power supply boards.   

[MarkL]

So I saw this thread here: https://www.eevblog.com/forum/repair/another-2465-300mhz-to-repair/

Now mine had exactly the same problem! So I decided to replace the CRT(made in '83 which was given a crooked picture and got damaged), the high voltage board....and then the main board.

But when I put it all back together, not only is the CRT black, but the panel LEDs won't turn on! Before I replaced the main board, the panel leds would turn on but the CRT would not. Now I checked all the capacitors on the low voltage/power supply board and they display the proper readings. I also notice that when I take current readings with my multimeter on the the pins that attack the power ribbon harness to the main board the readings are exceedingly low(even though the voltage readings are what they should be).
...

The problem in that post was due to a stuck beam finder.  Did you check your beam finder?

In troubleshooting if you perform a step that makes the problem worse or adds a new problem, UN-DO what you just did.  Don't create more variables to troubleshoot by changing more and more things.

In your case, I would at least put the old main board back unless you know for a fact the old board was bad.  And if you got something on the CRT with the old HV board, even if it was distorted, I'd put that back too and start again from there.

How do you know the replacement CRT is ok?  What made you think it was the CRT?

How did you take "current readings" on all those power supply voltages with your multimeter?  If you used the current scale on your multimeter and measured ACROSS the power supply pins, you could have blown one or more internal fuses.  Check to make sure you still have proper voltages on all rails.

[med6753]

Mark's advice is even better than mine. Go back and un-FUBAR what you replaced and get the scope back to the original failing state and do more detailed troubleshooting rather than the "shotgun" approach.

Are you using the correct service manual? If you indeed have a 2465 it needs to be a 2465 manual. Not the "A" or "B" suffix. They are different. If you don't have the correct manual flip me an e-mail and I'll send it to you.

Step 1 is verifying that the Regulator and Inverter Boards are functioning properly. You can get a good read of these boards via J119 on the Main Board. See Page 5-3, Table 5-1 of the service manual. It doesn't check some of the unregulated voltages coming off the Inverter Board but chances are if everything on J119 is good they will be OK too. And of those voltages on J119 the critical ones needed for the CRT circuits are +15V, -15V, +42.4V, and +87.