Author Topic: Oscilloscope Tektronix 2465 don't turn on  (Read 10839 times)

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Offline Giovanni28

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #25 on: September 30, 2015, 10:09:06 pm »
All the front panel lights are on.  It's not getting through the boot process.

I would go back and start again with checking the DC power supply outputs, as Bryan had described in post #10 in this thread.

https://www.eevblog.com/forum/repair/another-2465-300mhz-to-repair/

Sorry, but in the post there is no Bryan.
 

Offline MarkL

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #26 on: September 30, 2015, 10:14:36 pm »
Sorry, but in the post there is no Bryan.
I was referencing Bryan's post #10 where he had already recommended looking at DC voltages:

https://www.eevblog.com/forum/repair/crt-adjustment-tektronix-2465/msg760826/#msg760826

Which then points you to the other thread.  I was just saving a step.
 

Offline Giovanni28

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #27 on: September 30, 2015, 11:13:13 pm »

I apologize MarkL.

I think unmount all over again, to check the welds, welded components and if by chance I'm wrong in the assembly of something else.

Is it possible that the change of the capacitors, involves a few problems of calibrations?

How do I disable the CRT to make sure that does not come off, but I do voltage measurements?


« Last Edit: October 01, 2015, 12:06:31 am by Giovanni28 »
 

Offline MarkL

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #28 on: October 01, 2015, 12:01:48 am »
Changing the power supply capacitors shouldn't change your calibration.

Do you hear relays clicking when the scope is turned on?  Or do the front panel lights all turn on and then stay that way?

Are any knobs or switches responding?

I can't emphasize enough that the right place to start with a problem like this is to check the power supply outputs.
 

Offline Giovanni28

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #29 on: October 01, 2015, 12:19:12 am »
Do you hear relays clicking when the scope is turned on?  Or do the front panel lights all turn on and then stay that way?

I don't hear Relay clicking when the scope is turned on. Initially all the lights are not on.
Any knobs or switches not responding.

Although the picture of the display appears a very bright, it is actually a very short line very bright.


How do I disable the CRT to make sure that does not come off, but I do voltage measurements?
« Last Edit: October 01, 2015, 12:22:33 am by Giovanni28 »
 

Offline Giovanni28

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #30 on: October 01, 2015, 12:26:37 am »
However I have not changed only the power supply capacitors, but also those of the motherboard A1.
The oscilloscope worked well before replacing electrolytic capacitors on the motherboard.
« Last Edit: October 01, 2015, 12:33:55 am by Giovanni28 »
 

Offline MarkL

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #31 on: October 01, 2015, 01:54:03 am »
Do you hear relays clicking when the scope is turned on?  Or do the front panel lights all turn on and then stay that way?

I don't hear Relay clicking when the scope is turned on. Initially all the lights are not on.
Any knobs or switches not responding.

Although the picture of the display appears a very bright, it is actually a very short line very bright.


How do I disable the CRT to make sure that does not come off, but I do voltage measurements?
Probably the easiest way is to turn down the grid drive on the HV supply card.  Mark it before you move it so you can put it back.

If this doesn't have enough range, you could disconnect the high voltage connection going to the CRT anode.  Be careful since the anode will hold a high voltage charge.

Alternatively, just get your voltage checks done quickly.
 

Offline Giovanni28

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #32 on: October 01, 2015, 11:52:31 am »
Because before the replacement of electrolytic capacitors on the motherboard A1, tensions were the right ones and then instead should have been changed?
 

Offline Giovanni28

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #33 on: October 01, 2015, 03:07:57 pm »
Somehow, I do not know why, but now the oscilloscope works perfectly! Great.
 

Offline Giovanni28

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #34 on: October 08, 2015, 10:18:18 pm »
I sang victory too soon! 😂 Unfortunaltely, this evening I turned on the oscilloscope and the problem recurred




It definitely something wrong has reassemble. Can you help me please.

I turned off and then turned back on and the problem has apparently disappeared.
 

Offline Giovanni28

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #35 on: October 08, 2015, 10:32:59 pm »
1) There is still something that I think should not be. Look at the following pictures. When I press the button beam find, this is what happens:


2) If I put on CH1 and CH2 two sinusoidal signals both from 1kHz and 5Vpp, here is what presents itself to me. Is the phase shift normal?



3) With the same previous configuration, in XY mode, this is the figure. As you can see is not perfectly circular.

 

Offline guido

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #36 on: October 08, 2015, 11:11:42 pm »
That is not good, they should overlap. In XY also, a line at 45 degrees.
 

Offline Giovanni28

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #37 on: October 08, 2015, 11:16:02 pm »
That is not good, they should overlap. In XY also, a line at 45 degrees.

Do you have any suggestions?
 

Offline guido

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #38 on: October 08, 2015, 11:38:01 pm »
Check the supply voltages (always first thing on the list). Have one myself, it's a complicated beast. Had to fix several issues and replaced the supply caps.

Suggest to get the service manual and start digging. There is also a tekscopes yahoo mail group with a lot of knowledge.
 

Offline MarkL

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #39 on: October 09, 2015, 02:29:43 pm »
That's very strange.  There's about 300us of delay or phase shift between the two channels.

Is the delay the same at all input frequencies?

Just to be sure, this is the EXACT same signal coming into both channels?  The BNC cables are in parallel?


As for the problem coming back, try to see if you can make it happen.  Perhaps it's something mechanical.

If it's still a mystery but it happens anyway, look at the power supply levels while it's happening.  If those are ok, start looking at the processor troubleshooting sections.  Verify the processor reset control is working ok.
 

Offline grumpydoc

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #40 on: October 09, 2015, 04:01:42 pm »
Quote
Somehow, I do not know why, but now the oscilloscope works perfectly! Great.
I hate it when that happens - I much prefer to diagnose a fault and fix it

Things are more likely to stay fixed that way.
 

Offline Giovanni28

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #41 on: October 09, 2015, 04:37:45 pm »
That's very strange.  There's about 300us of delay or phase shift between the two channels.

Is the delay the same at all input frequencies?

Just to be sure, this is the EXACT same signal coming into both channels?  The BNC cables are in parallel?

You are right. I had not entered two signals in parallel. I apologize.

Quote
As for the problem coming back, try to see if you can make it happen.  Perhaps it's something mechanical.

If it's still a mystery but it happens anyway, look at the power supply levels while it's happening.  If those are ok, start looking at the processor troubleshooting sections.  Verify the processor reset control is working ok.

For the rest, I think you're right. I will have to disassemble again.

Thank you, very much.

« Last Edit: October 09, 2015, 05:10:42 pm by Giovanni28 »
 

Offline FlyingHacker

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #42 on: October 09, 2015, 05:53:48 pm »

You are right. I had not entered two signals in parallel. I apologize.


So is it working correctly with them in parallel?
--73
 

Offline Giovanni28

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #43 on: October 09, 2015, 07:30:54 pm »

You are right. I had not entered two signals in parallel. I apologize.


So is it working correctly with them in parallel?

Yes.
 

Offline Giovanni28

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Re: Oscilloscope Tektronix 2465 don't turn on
« Reply #44 on: February 12, 2020, 09:23:03 pm »
Eventually I managed to repair the oscilloscope.
 


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