Tektronix 2465B repair. - Page 1
Forum section: electronics / repair

author: neo
author_rank: Super Contributor
timestamp: April 19, 2018, 02:43:51 am
content: First a disclaimer, this is from 1990 making it the newest thing i own. I'm used to working on 1970s and older, so while i'm not incapable i may act a bit like a bit of an idiot but i'mcompletelymostly capable.I changed the capacitors on a5 and power supply, previously it worked now it doesn't. The only thing it does do is blink it's front lights at me and spin the fan, which i was hoping would point somewhere but apparently it doesn't. Going to check voltages now.Now tinkering on UFO parts and technology.(at least compared to usual.)

author: car46999
author_rank: Newbie
timestamp: April 19, 2018, 03:10:24 am
content: Neo,This is exactly what happened to mine just a few weeks ago (I only did the A5).https://www.eevblog.com/forum/repair/help-repairing-a-tektronix-2465b-a5-board/Do your front panel lights blink in a set pattern and then end with the "ADD LED" illuminated? If it does your scope is failing its power on checks.You can try adjusting the grid bias up, this may get your screen to start displaying info again and give you an idea of how to proceed.I hope I found my problem with mine, but I will not know for sure until next week when the replacement parts arrive. I used hot air to remove some of the components, I think this caused some cold solder joints on my U2101 chip.

author: car46999
author_rank: Newbie
timestamp: April 19, 2018, 03:12:46 am
content: This is the post that I found that helped me get to where I am now.https://groups.io/g/TekScopes/topic/2465b_stuck_in_selftest_add/7658233?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,1160,7658233

author: neo
author_rank: Super Contributor
timestamp: April 19, 2018, 03:42:07 am
content: Quote from: car46999 on April 19, 2018, 03:10:24 amIt blinks all of them at once, all on, all off, all on and then it will just go on like that. Seemingly timed to where it's equal periods off and on.

author: z01z
author_rank: Regular Contributor
timestamp: April 19, 2018, 06:55:04 am
content: Checking the voltages is a good idea. I'd also double check if all the connectors are reconnected.There are troubleshooting flowcharts in the service manual, in section 6 (maintenance).

author: mnementh
author_rank: Super Contributor
timestamp: April 19, 2018, 03:34:41 pm
content: IIRC, this is caused by the 5V rail not coming up; the PSU section attempts to power up, it fails the "POWER GOOD" test and goes into shutdown and continues to cycle this way until power is shut off or the fault is repaired. If it got any further, the unit would begin its CPU/Acquisition POST and send error codes to the screen and serial port.[EDITED TO CLARIFY]A fault in any of the main voltage rails can cause this; look for shorts or open circuit on all main power rails. Go back through all the work you did on the DC-DC converter board and the A5 board. Look for shorts/opens/incorrect voltage on the main power rails at both the DC-DC converter and the A5 board where you worked. Look for cables plugged in wrong too.I've attached a short dissertation on the very repair you just did, and I can eMail you the Tek Troubleshooting Oscilloscopes Training Manual (Older analog Only; will not have any digital systems troubleshooting) and Tek XYZs of Oscilloscopes Primer that are seminal reading in both servicing all 'scopes and how they work so you know how to get the most out of them.Here isKO4BB's archive of service manuals and resources for the 2465B/2467B. Please don't forget to give back a little via the button; hosting those documents isn't free and you can skip Starbucks or McD's for a day.Cheers,mnemNeeds more cowbell.

author: neo
author_rank: Super Contributor
timestamp: September 05, 2019, 08:27:03 am
content: OK, trying to get back at this after a long hiatus from electronics and i have two confessions to make.First, this damned thing is what drove me away to begin withSecond, I don't understand it and that pisses me off. I've spent 4 hours with the manual this time and ISTILLdon't know where to probe for voltage.I may have made some progress. No voltage outside the power supply, power supply seems to be ticking and I think I've ruled out the interconnect.

author: tggzzz
author_rank: Super Contributor
timestamp: September 05, 2019, 08:45:06 am
content: Quote from: neo on September 05, 2019, 08:27:03 amMy 2445b manual has it in section 5, subsection "power supplies and dac ref adjustments", table 5-1.I would be surprised if the 2465b was significantly different.Caution: observe there are differences for s/n numbers >b050000 and <=b049999.

author: neo
author_rank: Super Contributor
timestamp: September 05, 2019, 09:35:48 am
content: Quote from: tggzzz on September 05, 2019, 08:45:06 amStill wasn't able to find it until I watched this.https://youtu.be/Rp-0FqxQkBwI'm left wondering why they put the test point as far away from the power supply as possible.No voltage measured, at all.

author: tggzzz
author_rank: Super Contributor
timestamp: September 05, 2019, 09:46:33 am
content: Quote from: neo on September 05, 2019, 09:35:48 amDo you actuallyhavea service manual? If not, I recommend the scans from ArtekMedia as being high quality and affordable. Downloads are ~$10.There must have been a measured voltage, unless your meter is broken (or you didn't make two correct connections). Doubly so if the PSU is ticking.

author: neo
author_rank: Super Contributor
timestamp: September 05, 2019, 09:51:57 am
content: Quote from: tggzzz on September 05, 2019, 09:46:33 amhttps://www.atecorp.com/atecorp/media/pdfs/data-sheets/tektronix-2465b-2467b_manual.pdfAnd I know I''m an idiot but I copied Dave here. Clipped ground to chassis and probed the right pins. No measured voltage. All the board interconnects are plugged in, I checked that too.

author: tautech
author_rank: Super Contributor
timestamp: September 05, 2019, 09:54:25 am
content: This is worth having too:http://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf

author: tggzzz
author_rank: Super Contributor
timestamp: September 05, 2019, 10:01:14 am
content: Quote from: neo on September 05, 2019, 09:51:57 amWell, that manual has the information in it.I guess by "no measured voltage" you really mean you were measuring 0.000V.The PSU ticking indicates that it is trying to startup, and is failing for some reason or other. That's not an uncommon problem, so googling will indicate how you should proceed. Be aware that parts of the PSU are directly connected to the mains supply, and other parts have high voltages.

author: neo
author_rank: Super Contributor
timestamp: September 05, 2019, 12:04:36 pm
content: Capacitor was in backwards, didn't explode but it did keep it from working. Fixed, now all voltages are correct but now it's something else, all lights come on and fan goes full blast.I'm not an idiot, a backwards capacitor happens to the best of us.And the fact it took you 6 hours? (voice inside my head)I'm used to the 70s....

author: tggzzz
author_rank: Super Contributor
timestamp: September 05, 2019, 12:18:41 pm
content: Self-diagnostics consist of the lights that are on plus the test/exerciser routines that display results on the CRT.We all make stupid mistakes. Many times I've come back the next morning and wished I'd stopped work an hour earlier.

author: neo
author_rank: Super Contributor
timestamp: September 05, 2019, 12:27:24 pm
content: Right, the problem being is that the crt doesn't come on and the lights stay on. I get a brief flash on the crt then nothing. And I just checked, all the ripple is within spec.Edit;I know for a fact that there is no cal data, but it should do a bit more than this shouldn't it?

author: grbk
author_rank: Contributor
timestamp: September 05, 2019, 03:21:04 pm
content: Do the diagnostic lights do anything?I had electrolytic damage to the A5 board and the CRT behaved like you describe on powerup. Even though the CRT wasn't on I was able to tell which diagnostic it was failing based on the front panel lights. The details of how to decipher them are in the service manual. In my case, the diagnostic indicated a problem with the DAC circuit which is typical for electrolyte damage to A5.See my post in the 2465 thread for details.

author: neo
author_rank: Super Contributor
timestamp: September 05, 2019, 08:05:44 pm
content: The front panel lights, they come on and stay on. That's it, I've even let it be for a few minutes and nothing more has happened.Edit; once upon a time, before I changed the caps actually, this scope worked.

author: grbk
author_rank: Contributor
timestamp: September 05, 2019, 08:17:00 pm
content: Which lights come on and stay on? The particulars will tell you if it's getting through the self test, and if not, which test fails. If a test is failing, that will in all likelihood point you at the problem.This is described briefly in the service manual on page 6-7, and in detail (including how to interpret failures) beginning on 6-10.

author: neo
author_rank: Super Contributor
timestamp: September 05, 2019, 08:37:31 pm
content: All of them, or so it seems.

author: med6753
author_rank: Super Contributor
timestamp: September 06, 2019, 03:19:41 pm
content: It looks like it hung up trying to boot. Re-check all your interconnects from the Inverter/Regulator boards to your main board and A5 board. Also check J119 on the main board for the correct voltages. Report back.

author: neo
author_rank: Super Contributor
timestamp: September 10, 2019, 01:15:04 am
content: Quote from: med6753 on September 06, 2019, 03:19:41 pmSorry for the delay, juggling a vacation with a parts order and this red headed child.All voltages present, all ripple within spec. The interconnects have been checked a dozen times easily and I've even tried replacing a couple suspicious looking ceramic caps. No dice, still the exact same thing.And trying to read this manual gives me migraines. TOO. MUCH. DATA. Maybe if it was properly searchable....

author: tggzzz
author_rank: Super Contributor
timestamp: September 10, 2019, 06:20:12 am
content: Quote from: neo on September 10, 2019, 01:15:04 amThe artekmedia scans are searchable to the extent that any pdf can be searchable, and the pages are properly indexed. Pay the $15 or whatever, wait a day, and download it.