Tek 2465b serial number B0506** Dallas NVRAM - Page 1
Forum section: electronics / repair

author: JohnTinkers
author_rank: Contributor
timestamp: August 04, 2025, 10:47:16 pm
content: I picked up one off of eBay that works like a charm and looks like it was kept in a shrine and worshipped. It’s a beauty! Serial number in the mid 50,000s. It still has uncut cal stickers on it!!I have ordered up Kemet safety caps to replace the RIFA caps. I will also check every other cap in the scope, after watching Dave fix one up that was given up for scrap.But in the service manual, I noted that the scope has the dreaded Dallas 1225 NVRAM chip. Just one.Reading further, the manual speaks of the chip holding dot patterns for characters that display on the screen, but not for any calibration values. This makes sense because the cal is seemingly done with trim pots. That brings up the question: what to do?Do I lose the scope if the NVRAM battery fails? Do I replace it with FRAM? I saw a YouTube person fail at this using a breakout board from PCBWay and a FM16W08. If this contains character buffers and not shapes, it seems that it should re-initialize when the scope reboots. But I may be wrong, so I’m reaching out to the community.Any help you guys might be able to toss my way would be highly appreciated. Thanks!!John.

author: tggzzz
author_rank: Super Contributor
timestamp: August 05, 2025, 07:25:29 am
content: Have fun with it.Hope those are the original cal stickers. Apparently there's a bastard on fleabay who "turns" 2445bs into almost-2465bs, and use his cal stickers to prevent people looking inside and detecting his lies. Even if you do have one of those, I imagine it will still be a nice scope.Look at the 2465a/b info on this site and TekScopes. The 2465 is different, better in some ways and worse than others.Get the service manual from BAMA, ko4bb, tekwiki.Key failures: RIFA, PSU electrolytics (see condor audio document; he sells kits on fleabay), A5 SMD electrolytics, DallasRAM.The Dallas holds calibration constants (important) and the last position of the front panel controls (unimportant). When you first switch it on, if there are no spurious dots on the screen the RAM cal constants - so point a video camera at the screen and use the test 44 routine to capture the values. Those can be fed back into any replacement Dallas RAM.

author: JohnTinkers
author_rank: Contributor
timestamp: August 05, 2025, 02:40:45 pm
content: Quote from: tggzzz on August 05, 2025, 07:25:29 amHi --I have the manual in PDF format and even OCR overlaid it to make it searchable. I think I got it from Tekwiki.The cal sticker is from Tangent Labs, which is apparently a known good lab. I may reach out to see if they have a record of cal for my serial number.I will look for that Electrolytic cap kit, although I'm tempted to keep Mouser busy selling me caps.The screen is free of weird dots.The eBay seller has a very good reputation, with no complaints about non-genuine or mislabeled scopes.Thanks for taking the time to provide such an excellent and detailed answer.ThanksJOhn.

author: tggzzz
author_rank: Super Contributor
timestamp: August 05, 2025, 02:49:49 pm
content: I like it when someone is ahead of me, with good answers

author: TERRA Operative
author_rank: Super Contributor
timestamp: August 05, 2025, 03:02:42 pm
content: I recently replaced a Dallas NVRAM with an FRAM in a 2465B recently, the scope needed the usual capacitor replacement and repair of the PCB around the SMD caps.There's a pdf document floating around on the details of the FRAM swap and calibration and other bits of useful info.https://www.worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdfHere's the PCB I designed to do it.https://www.pcbway.com/project/shareproject/Dallas_DS1225Y_FRAM_Adapter_3c961bed.htmlI copied out the data from the old Dallas NVRAM and copied it into the FRAM which worked fine, but I decided to run it through a cal procedure anyway as it was well due for it.

author: JohnTinkers
author_rank: Contributor
timestamp: August 05, 2025, 03:30:57 pm
content: Quote from: TERRA Operative on August 05, 2025, 03:02:42 pmHi --Thanks for the links! I love your YT channel and have seen your work with Dallas NVRAM! I've decided to use your solution, and will be ordering the boards from PCBWay this week, and the FRAM from our friends at Mouser. I may have 4GTE.com do the cal once the scope is fully serviced. They are close to my home.

author: Kwakerman
author_rank: Regular Contributor
timestamp: August 05, 2025, 05:12:58 pm
content: I'd ask the Cal company what they will do for the price. Some companies will just check the scope against the published tolerances and if ok give it a 'pass' and if not a 'fail'. The alternative is a Cal with adjustments (where nesessary) but that is a lot more time and effort (and cost). I've got all the kit to do a cal (and have done it many times over the years across the 24x5 range) but to run one through a full cal from scratch can take a few hours to do.

author: Kwakerman
author_rank: Regular Contributor
timestamp: August 05, 2025, 05:17:55 pm
content: Also make sure the caps on the A5 have been replaced and there is no signs of corrosion on the PCB. The general area that is affected by corrosion is the around the DAC. If you have just had it Cal'd and then have issues with the A5 that requires a DAC rebuilt you will effectively compromise some areas of your Cal as you will have to reset the DAC voltages.

author: JohnTinkers
author_rank: Contributor
timestamp: August 05, 2025, 05:28:29 pm
content: Quote from: Kwakerman on August 05, 2025, 05:12:58 pmHi --I'd love the challenge, but I lack the gear and am having problems finding the Tek plug-ins that are necessary. I also thought of asking ZenWizard for a quote to cal and adjust; he is a genius and would get it spot-on. So I thought to get a quote from 4GTE.

author: TERRA Operative
author_rank: Super Contributor
timestamp: August 05, 2025, 11:36:40 pm
content: Make sure to fully check any corroded traces for continuity if the SMD caps have leaked on the A5 board!I had to replace a trace or two on the one I recently repaired, but it's working perfectly again now.

author: JohnTinkers
author_rank: Contributor
timestamp: August 06, 2025, 03:20:18 pm
content: Quote from: TERRA Operative on August 05, 2025, 11:36:40 pmThanks! I will carefully check and also proactively replace. The capacitor police will be thrilled!ThanksJohn.

author: JohnTinkers
author_rank: Contributor
timestamp: August 13, 2025, 03:53:23 pm
content: Quote from: TERRA Operative on August 05, 2025, 11:36:40 pmHi - I now have the PCBs in house, and am getting the FRAMs from Mouser. I got the round pin headers, 28-pin DIP sockets. I also have the replacement safety caps, and will be popping the scope open this weekend.Sorry to bother but I do have some questions...Is a GQ-4X a good choice to read the old Dallas and to write in the FRAM?In the 3458 video I thought I heard you say that you needed to program the FRAM while it was not on the PCB. Does that hold for the 1225 adapter too?I will read off the Cal settings using the Test 44. If there is a failure with the SRAM and NVRAM is there a process to re-enter those cal constants or at that point am I stuck to do a complete cal and adjustment?Again, thanks for your heroic support of the community!John

author: TERRA Operative
author_rank: Super Contributor
timestamp: August 14, 2025, 12:32:34 am
content: Some of these questions I can answer.....1. Unfortunately I have no idea as I use the Xgecu brand programmers, which work well for me so I never looked further.2. My 1225 adapter is a direct SMD to DIP adapter, so the chip programs perfectly as normal.3. I'm not sure if you can re-enter the cal constants or if they need to be reprogrammed directly into the chip, I've never tried as I usually just recalibrate the scope anyway (I have all the gear to do so). A deep dive into the service manual might turn up, or ask the question on the tekscopes groups.io page.https://groups.io/g/TekScopes/topics

author: JohnTinkers
author_rank: Contributor
timestamp: August 14, 2025, 03:54:10 am
content: Quote from: TERRA Operative on August 14, 2025, 12:32:34 amThanks! Just picked up a XGecu T48!

author: Kwakerman
author_rank: Regular Contributor
timestamp: August 14, 2025, 08:58:18 am
content: I do not believe it is possible to manually re-enter the Cal constants with the Dallas or Fram installed in the scope, that process needs to be done with the chip in a programmer then the chip is reinstalled into the A5

author: TERRA Operative
author_rank: Super Contributor
timestamp: August 14, 2025, 12:08:28 pm
content: Would be cool to write a python script to build the image to flash the chip from the cal constants.A bit out of my ability, but I'm sure it could be done.

author: Kwakerman
author_rank: Regular Contributor
timestamp: August 15, 2025, 07:31:10 am
content: I wonder if that could be done via the GPIB too. I know some kit allows you to dump cal constants via GPIB so perhaps the reverse could be true. Also outside of my ability and I have enough kit to sort out without a second distraction!

author: JohnTinkers
author_rank: Contributor
timestamp: August 21, 2025, 08:32:48 pm
content: OK, this is interesting. I popped open the scope and looked at board A5. and there are no SMD electrolytics on it! There are some SMD caps there, see photos, and one THD electrolytic. My first thought was one of dread. One other person here posted up that there was a scammer on eBay who was modding 2445B scopes into fake "2465B" and selling them on eBay.I don't know if this is a different edition of the board; it somewhat closely resembles the 2465b board for SN 50360+ (my scope is 50600), but the rest becomes a bit confusing. The dates on the SMD ICs are almost all 1989 second quarter. This includes the (ugh) Dallas memory chip.I don't know precisely how to diagnose if this is a scam scope that was modded and rebadged. All I do know is that the caps in the unit's A5 board look quite good and are THD electrolytics or block SMD caps. The caps do NOT look retrofitted to me.I'd appreciate thoughts. It can be attractive YouTube comments, with the "I was scammed" lead in and thumbnail, but I don't know if I am experiencing this phenomenon. I'm reticent to change out the Dallas NVRAM chip at this time until I do know.Any telltale ways to see if it is a lesser model that was modded to a 2465b?Here are the images...[ Specified attachment is not available ]ThanksJohn.

author: JohnTinkers
author_rank: Contributor
timestamp: August 21, 2025, 08:46:15 pm
content: Less Dread. Combing through the 2465B Manual I found this:This is IDENTICAL to the observed layout on my A5 PCB.I still want 100% assurance that this is not a retrofit 2445B but I am much less worried, and am preparing to replace the Dallas with the FRAM.I will run the diag suggested above, and then make SEVERAL backups of it using the XGecu (Thanks to NFM for the pointer) and compare and then fill the FRAM. Once that works, then I will take the unit apart to get to the RIFAs.If the Dallas transplant fails, then I need to find a leveled Sinewave Generator and a time mark generator, or make @Zenwizard a rich man.ThanksJohn.

author: Kwakerman
author_rank: Regular Contributor
timestamp: August 21, 2025, 09:02:31 pm
content: If you want to be sure what version scope this is look at the part numbers on the A1 (main PCB) and the A5 then compare them to the ones listed in the service manuals for the 2445A/B and 2465A/B.

author: Kwakerman
author_rank: Regular Contributor
timestamp: August 21, 2025, 09:07:41 pm
content: Another trend I've noticed is that the B models are normally fitted with Torx screws and the A models and earlier have Philips headed screws. Not sure if this is a rule as such but I've probably worked on 50+ of these 24X5 scopes and it seems to hold true.

author: JohnTinkers
author_rank: Contributor
timestamp: August 21, 2025, 09:15:53 pm
content: Quote from: Kwakerman on August 21, 2025, 09:07:41 pmThis is a totally Torx unit.

author: MarkL
author_rank: Unknown
timestamp: August 21, 2025, 09:19:40 pm
content: A couple of links to answer some of your questions...Read this thread on how to identify bogus modded 2465B scopes:https://groups.io/g/TekScopes/topic/7658884#140202Backup and restore of calibration values using GPIB:https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg4750262/#msg4750262Restore calibration values without GPIB (uses EPROM programmer):https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg5513656/#msg5513656Also, I'll add my $0.02 and say that I do not recommend directly replacing the Dallas chip (and in some models the battery) with a drop-in FRAM. The power up/down sequence *required* by the FRAM is not implemented by the existing Dallas circuitry and can result in data corruption. That being said, it does work by luck for the vast majority of users. Whatever you decide, keep a backup by taking a video while stepping through the cal data display in EXER 02, as already mentioned.

author: JohnTinkers
author_rank: Contributor
timestamp: August 21, 2025, 09:22:28 pm
content: Quote from: Kwakerman on August 21, 2025, 09:02:31 pmOn A5 you have U2360. In the 2445B manual it is 160-5877-00 and 2465B manual it is 160-5877-01The chip is labeled 160-5877-01!Methinks that we have a genuine 2465b.Thanks for that pointer!!!!!!!John.

author: JohnTinkers
author_rank: Contributor
timestamp: August 21, 2025, 09:37:44 pm
content: Quote from: MarkL on August 21, 2025, 09:19:40 pmThanks! I am jumping with joy because I followed your advice and found on the A1 board the absolute proof that this is a real 2465b:The Circled "transient Response" is on Board A1 and only in the 2465b and 2467b. So you are a steely-eyed missile man.Quote from: MarkL on August 21, 2025, 09:19:40 pmI'm interested to hear more about this. Checking Digikey, Newark and Mouser for new DS1225Y chips. Given that the dallas chip is 36 years old, I need to act fast on this.Again, thanks for the link, which quickly made my day.John.

author: MarkL
author_rank: Unknown
timestamp: August 21, 2025, 10:37:53 pm
content: Quote from: JohnTinkers on August 21, 2025, 09:37:44 pmYou also appear to have the mentioned "G" drawn on the PCB.QuoteIn short, the scope's power up/down NVRAM safety is predicated on the DS1225Y locking out all access at Vdd < 4.5V, and the FRAM doesn't do that. There's two basic hazards:1) The scope's reset circuitry does not guarantee non-spurious processor operation below 3.6V, and at this voltage the FRAM is still fully operational, and,2) The FRAM requires that /CE follow Vdd down to 0V to prevent access below the FRAM's minimum Vdd of 2.7V, which the scope's circuitry does not implement.Either one of these can cause corruption. If you want to read more about it, there was a thread on tekscopes:https://groups.io/g/TekScopes/topic/79943568I would replace a dead component with the same, if it's still available, and stay compliant with the original design.

author: JohnTinkers
author_rank: Contributor
timestamp: August 22, 2025, 03:37:53 am
content: Quote from: MarkL on August 21, 2025, 10:37:53 pmNow I find myself thinking of picking this up:https://www.mouser.com/ProductDetail/Analog-Devices-Maxim-Integrated/DS1225AD-150%2b?qs=0Y9aZN%252BMVCWSdATgHtfGHw%3D%3DThis is supposed to be a drop in.

author: JohnTinkers
author_rank: Contributor
timestamp: August 22, 2025, 04:40:09 pm
content: Quote from: MarkL on August 21, 2025, 10:37:53 pmI reread the thread, and thought that the "G" meant it was a 2445b. So I checked and at the end I am now 100% sure that this is a legit 2465b scope through and through. The A1 board is matched to the modelandserial number of the scope, and this is verified with the service manual. So we have the telltale pot, and the correct part number for the board for the model and for the serial. The 2445b has a completely different part number.So that is closed.Since I have the NFM board in house, and the FRAM chips too, I will read in the DS1225Y into the XGecu (3X with verification) and flash the FRAM. I will put that in and keep a close eye. If it goes sideways, then I will get a DS1225AD from Mouser and flash that and install it.As an aside, I peeked at the power supply, and it isurgentto replace the safety caps. I will power it up only long enough to obtain the cal constants to video, and then power down, and then get busy. I have the safety caps in house now.ThanksJohn.

author: Kwakerman
author_rank: Regular Contributor
timestamp: August 22, 2025, 07:33:40 pm
content: There can be up to 5 RIFAs in the PSU, 2 on the mains input PCB (A2A1) and 3 on the other PCB (A3) under the metal cover. Depending upon the build standard some of these caps may have been replaced with non-RIFA from the factory so don't worry if you don't find the full 5, just check the positions listed below.From my old records I think they are A2A1C1016, A2A1C1018. A3C1020, A3C1051 and A3C1052.

author: JohnTinkers
author_rank: Contributor
timestamp: August 22, 2025, 08:22:58 pm
content: Quote from: Kwakerman on August 22, 2025, 07:33:40 pmThanks; these match with my read of the BOM when ordering replacements. Oddly, I ordered KEMET caps from Mouser, and what I got were modern RIFAs! Did not know that KEMET bought RIFA 18 years ago!:OI will post pics and video links.ThanksJohn.

author: JohnTinkers
author_rank: Contributor
timestamp: August 27, 2025, 05:47:56 pm
content: Get this! I tried to order a 1225AD from Mouser and they put my order on Hold! They said that it was a "payment hold" but the order was already billed to my card. On chat I got this load of nonsense!

author: JohnTinkers
author_rank: Contributor
timestamp: August 27, 2025, 06:20:34 pm
content: Mouser found a drop in compatible from ST Microelectronics!!M48Z18.I will report how it works to the group.ThanksJohn.

author: Kwakerman
author_rank: Regular Contributor
timestamp: August 27, 2025, 08:51:23 pm
content: Do they mean can't be used for personal accounts rather than business ones?If not, are you using a VPN on the Mouser site? They may think you are in a different country to the US and hence the restriction.

author: JohnTinkers
author_rank: Contributor
timestamp: August 27, 2025, 11:05:30 pm
content: Quote from: Kwakerman on August 27, 2025, 08:51:23 pmHi. They meant that personal customers are not allowed to buy the Dallas chip from Mouser. By the evil manufacturer.I did not use a vpn.But I did not find the compatible NVRAM but for Mouser helping me out and hunting it down.

author: tchicago
author_rank: Regular Contributor
timestamp: October 02, 2025, 02:40:26 am
content: Quote from: JohnTinkers on August 27, 2025, 11:05:30 pmThe Digikey just shipped DS1225AD to my personal address just fine. Also for the use in 2465B. The Fedex shipping rate though was upgraded to a more expensive one that permits lithium batteries :/