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 Post subject: Tektronix 2430A Fails Repet
PostPosted: Mar Sun 29, 2020 2:29 am 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 626
Location: Cedar Rapids, Iowa
I recently picked up a Tektronix 2430A for next to nothing because it had failures on the self test. Most of these failure were caused by a dead backup battery. I found a suitable replacement and installed it and that got me past most of the failures. It still failed 9000 Trigs on the extended diagnostics. I did the ext cal on the atten, triggers, and repet...atten and triggers passed, but repet failed. I opened it up and looked it over carefully and found an electrolytic cap on the low voltage power supply board that was bulged on top, so I removed it and tested it. It was a 2200uF cap that read 15uF, so I ordered and replaced all electrolytics on the low voltage power supply board but it made no difference. It still has these failures:

9113 Slope
9123 Slope
9300 Trigs/Repet

And I don't have a nice straight trace...this is what I have:
Attachment:
display_006_r.jpg
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The displays changes as it should when the time base is changed but not when the volts/div is changed, even though the readout showing the setting it's on does change as it should.

Can someone point me in the right direction on this? I do have a pdf of the service manual.

Thanks,
Rich


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 Post subject: Re: Tektronix 2430A Fails Repet
PostPosted: Mar Sun 29, 2020 4:50 am 
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Joined: Jan Thu 16, 2020 12:29 am
Posts: 486
The trace is being chopped up vertically into 4 different levels for periods of about 500uS. Probably this is a hardware fault unless there is a test or setting mode that causes this effect (I don't own this particular model myself)

It appears as though there is likely a fault in the vertical amplifiers where the channel switching is done. Likely you would need to sit down with another scope and the manual to go through it systematically to find the cause.


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 Post subject: Re: Tektronix 2430A Fails Repet
PostPosted: Mar Sun 29, 2020 12:47 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 6909
Location: Sunbury, Ohio 43074
I agree with the above, but also have no real idea if this is "normal" for the test that the scope is running. Have you tried one of the tektronix user groups? There are some real scope gurus over there that understand the software driven scopes very well.

https://groups.io/g/TekScopes

Try the above. If no one knows your particular scope, they will at least know where to send you next.

_________________
Preserving the hist. of electronics, one boat anchor at a time! :)
https://www.bbtvtestequipment.com


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 Post subject: Re: Tektronix 2430A Fails Repet
PostPosted: Mar Sun 29, 2020 9:23 pm 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 626
Location: Cedar Rapids, Iowa
Thanks guys! Barry - I did start a thread here: https://forum.tek.com/viewforum.php?f=568 But that was for the backup battery problem. Now that that has been resolved I'll start a new thread about the repet failure. The display I'm seeing is not normal for that test. I've seen video of the test being run and it should have a good solid trace. I'm getting that chopped trace no matter what I am doing.

Rich


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 Post subject: Re: Tektronix 2430A Fails Repet
PostPosted: Apr Thu 02, 2020 2:18 am 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 626
Location: Cedar Rapids, Iowa
Just as a followup on this...I did create an account and post this to https://groups.io/g/TekScopes. There were a few people that replied and tried to help, but one in particular that was quite helpful. I now have a fully functional Tektronix 2430A and have less than $50 into it :D Actually, there was nothing wrong with it once I replaced the backup battery and bad electrolytic cap, I just didn't know how to use it properly. I've been using my 2215 for about 35 years and this thing is quite different.

The image on the left shows that it passed all of the Ext Cal steps, and the image on the right shows that it passed all of the Ext Diagnostics.

Rich

*Edit* 04/02/20 Correct spelling error.


Attachments:
display_pass_r.png
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Last edited by criageek on Apr Thu 02, 2020 2:25 pm, edited 1 time in total.
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 Post subject: Re: Tektronix 2430A Fails Repet
PostPosted: Apr Thu 02, 2020 2:22 am 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 6909
Location: Sunbury, Ohio 43074
Glad to hear you got it working. Software driven test gear can be almost impossible to fix without help from a former factory tech, or someone that has seen "the problem" before. Personally I kind of hate it, although I do really like my 2445 lol. I cringe thinking about the day something goes wrong with it... back to the 465B I guess :). Or the 453

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Preserving the hist. of electronics, one boat anchor at a time! :)
https://www.bbtvtestequipment.com


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