problem with battery replacement in a tektronix 2445b oscilloscope - Page 1
Forum section: electronics / testgear

author: jsblues81
author_rank: Contributor
timestamp: February 22, 2022, 10:38:10 pm
content: Is there anybody out there who knows how to replace the internal battery and how to access it once found in a tektronix 2445b scope...thanks in advance for you help.

author: bdunham7
author_rank: Super Contributor
timestamp: February 22, 2022, 10:51:45 pm
content: It depends on whether or not you have an early or late version. The early version has an Eagle-Picher LTC-7P Li-Thionyl keeper battery installed on the A5 controller board. The later version has Dallas NVRAM with integral batteries and replacing those is much more involved. I believe if your scope is has a serial number below B049999 it will be the early version, provided it has not been modified.Edit: Here is a photo that shows both. If you're new to servicing these, do not run these scopes with the case removed unless you have a strong fan blowing on the entire underside.

author: jsblues81
author_rank: Contributor
timestamp: February 23, 2022, 04:58:02 am
content: Thanks for the fast response...My scope is #b050143 and has the dallas sram chip...any thoughts on how to approach this...I have been repaiuring and designing analog equipment for over 50 years but am relativly new to diugital,however I can handle tough problems so please your thoughts..thanks.

author: bdunham7
author_rank: Super Contributor
timestamp: February 23, 2022, 05:24:49 am
content: Has the battery gone dead and resulted in you getting a Test 04 failure when you start the scope? Or are you at some other point?There has been extensive discussion of replacing these NVRAMs here and elsewhere--search EEVBlog andhttps://groups.io/g/TekScopes/topicsfor detailed help on this. I do not know the current best solution nor what will work best for you. Buying a replacement Dallas NVRAM may not be a good option because they stopped making them long ago and your market choices are very old NOS (not good for something with a battery) and counterfeit. If you've lost your calibration data you will need to calibrate the scope once you are done, if not you need a programmer to copy over the info.

author: jsblues81
author_rank: Contributor
timestamp: February 23, 2022, 07:30:44 am
content: Thanks again...what was coming up upon bootup was test 05 fail 44. I am not sure exactly what that means...manual says positive level too positive.Whatever that could mean, I could think of a few things that could mean...but upon looking for a voltage on the control board, there are no voltages on any chip on any pin when the power is off. Is this too far gone...I bought this for $100 on ebay as is..please advise. I will however check the forums you suggested..thanks again.

author: jsblues81
author_rank: Contributor
timestamp: February 23, 2022, 10:33:54 am
content: Also...while on the 2445b subject...this scope may just have to be re-capped but I can't tell if someone did that for me. The caps in the power supply are all sprague blue atom looking caps and they look physically at least very "new". I know that doesn't mean much. Also the low mfd and pf caps on the other boards are all red wima poly style caps. Does anyone know if that is the stock arrangement or not...thanks again in advance.

author: bdunham7
author_rank: Super Contributor
timestamp: February 23, 2022, 03:05:18 pm
content: Quote from: jsblues81 on February 23, 2022, 07:30:44 amThe Dallas NVRAM battery is internal and you won't see an external voltage. That test failure is not related to loss of the calibration data AFAIK, I haven't run into it before. I think it is related to the trigger circuit, but you'd have to research that some more.Here's an EEVBlog thread on the topic:https://www.eevblog.com/forum/testgear/2465bct-error-test-05-fail-44-(24)-trouble/

author: grumpydoc
author_rank: Super Contributor
timestamp: February 23, 2022, 07:35:38 pm
content: Quote from: bdunham7 on February 23, 2022, 05:24:49 amAre you sure - I just bought a DS1225AD 70ns replacement from DigiKey (so I assume reliably sourced) and it arrived with a 2106 date code.

author: jsblues81
author_rank: Contributor
timestamp: February 23, 2022, 07:49:05 pm
content: Thanks again...I have been up since last night researching this and found the following...leaky smd caps (4) can cause this...check the dac reference...as you repied, a dead sram chip (mouser has it if it comes to thst...a damaged u500 (a and b trigger). If it is the chip it has been recomended by several post to use a fram in its place..(a forever fix as they put it). I can't think of any more right now...very tired. I apparently have some more research to do. TYhanks again for your support on this topic.

author: bdunham7
author_rank: Super Contributor
timestamp: February 23, 2022, 08:08:48 pm
content: Quote from: grumpydoc on February 23, 2022, 07:35:38 pmNo, I'm not sure at all! I've heard of counterfeits or other DOA NVRAM from dodgy sellers, but I don't know why I thought they were NLA nor why anyone would buy one from disreputable sources if they're available from DK or Mouser. Is that a drop-in replacement for the DS1225Y? Have they been available this whole time?

author: jsblues81
author_rank: Contributor
timestamp: February 23, 2022, 09:03:02 pm
content: What do you think of using a FRAM instead?

author: bdunham7
author_rank: Super Contributor
timestamp: February 23, 2022, 09:47:24 pm
content: Quote from: jsblues81 on February 23, 2022, 09:03:02 pmSomebody else should answer that since I haven't done that one of these. I think it is commonly done, but I've no idea how much more work it is. If the Dallas NVRAM is available, I'd probably just replace it and run a calibration. Look for the very long Tek 2465B teardown thread here or just do some searching--you'll find plenty of info on it. You also want to replace the SMD capacitors on the A5 board and clean it.

author: grumpydoc
author_rank: Super Contributor
timestamp: February 23, 2022, 10:49:26 pm
content: Quote from: bdunham7 on February 23, 2022, 08:08:48 pmI believe so, it's the Maxim part and you need to go for the "AD" suffix which has the same supply voltage spec as the original "Y" (5v ± 10%); anything faster than 200ns should be OK.Quote from: jsblues81 on February 23, 2022, 09:03:02 pmIt's worth reading the TekScopes mailing list archived postings (and, I believe, also threads passim on eevblog) about this. The problem with the FRAM is that there's no protection from spurious writes on power up/down as the DS1225 handles this internally. the result is that quite a few people have reported corruption of cal data when using an FRAM.I originally bought an FRAM to put in the 2445B that I repaired recently but having read through the old posts I decided to go for the Dallas chip instead.

author: jsblues81
author_rank: Contributor
timestamp: February 24, 2022, 08:30:04 pm
content: Hey guys...thanks loads for the support y'all gave to me but I've decided to pack this up and sell it on ebay as non-working or for parts to re-coup some of money spent and look for another 2465 which as I have read is very much superior and attempt to repair it now that I a little more knowledge..thanks to you then I had previous..I own 3 working 465b's and was just looking for something more up to date without going thru hoops to get it...wish me luck?

author: jsblues81
author_rank: Contributor
timestamp: March 23, 2022, 09:34:07 am
content: Hey y'all...its been awhile. I just purchased a 465b with serial number starting with 062.... so its a little later than my other ones. The image on the screen does not go all the way to the left edge and all the way to the right edge. It comes 1 graticule short on both right and left edges of the screen. Does anyone out there know whats the cause...hv problem or worse. The -2450v is present and even a slight bit high...all the low voltage supplies are fine with little or no ripple on any of them. Please advise...thanks in advance.

author: jsblues81
author_rank: Contributor
timestamp: August 08, 2023, 01:31:27 am
content: I am servicing my 2445b and suspect the DS1225Y-200 memory's battery is dead. I found a new one on e-bay. While I am waiting to recieve it...does anyone know what would be involved other than replacing it. I am relatively new to digital and need some assistance....if you could give me some links or other info...that would be greatly appreciated..thanks..js.