2465A CT - Backing up U2160 and U2260  - Page 1
Forum section: electronics / repair

author: jorgino
author_rank: Newbie
timestamp: June 24, 2024, 08:44:03 pm
content: Hi all,New member here, I have a 2465A CT o'scope from 05/06/1987. It is currently taken apart because I was going to recap the electrolytics (still mustering up the courage), and I thought this might be a good time to make a backup of the EPROM chips U2160 and U2260. Are there detailed instructions anywhere on how this can be accomplished on this particular o'scope? It is all original, the A5 board shows Tektronix 160-3302-08 and 160-3303-08 chips and Lithium LTC-7P battery. It didn't have any error messages on screen and booted just fine before I took it apart. The issue with this o'scope is that after a minute, the screen bounces like an earthquake so I thought maybe the lvps could be introducing some interference into the CRT circuit?After 2 minutes being powered on:https://youtu.be/g6iKEVwqY9M?si=HrbU4WPbew42cphBAnd here's the initial cold startup:https://youtu.be/TZBrt2rvHFA?si=zGpR9IwqGcGCr-WgWhat are your thoughts? By the way, getting the lvps in and out of this o'scope is like fighting Godzilla with a toothpick!!!!Thank you everyone!George

author: MarkL
author_rank: Unknown
timestamp: June 24, 2024, 09:49:23 pm
content: The two EPROMs can be downloaded from a number of archives, so I wouldn't be too worried about preserving copies of them. You really want to make a backup of the NVRAM so you don't lose your calibration constants.Because you have the GPIB interface, one way is to dump the calibration constants using this procedure:https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg4750262/#msg4750262If you don't have a GPIB interface on your computer, the next best thing is to take a video while scrolling through the calibration constants using "EXER 02" in the service menu. This menu is described in the service manual starting on page 6-15. Hopefully the screen will stay stable enough while you do it. Try to get the focus where everything is legible.As for the screen wobble, also in the service menu is how to check the power supply voltages and ripple (the latter probably being important in your case). It's described in table 5-1, and also in the troubleshooting flowcharts in the back.I'd also encourage taking some time to read the thread mentioned above. It's long, but contains a lot of debugging wisdom on this series scope.Manuals:https://w140.com/tekwiki/wiki/2465A

author: jorgino
author_rank: Newbie
timestamp: June 24, 2024, 11:11:01 pm
content: Quote from: MarkL on June 24, 2024, 09:49:23 pmHi Mark,I was hoping you'd reply, I did read most of that humongous thread and I noticed your collaboration there was paramount!So I naively assumed that the calibration constants were in those 2 chips, and they were powered by the Keeper II, but now I know the NVRAM is the U2460. I just downloaded the manual and I'll start reading it, as you can tell, I know next to nothing about this o'scope, even though I've had it stashed in a closet for close to 13 years. I don't have a GPIB interface, but I wouldn't be opposed to getting one if it's not too pricey, I'll start looking into that.At this point, what would your recommendation be? Put the o'scope together and get the cal constants via "EXER 02" or go ahead and replace the capacitors first since I already have it all apart?I did try to put it together last weekend and could not get that lvps board in for the life of me. Thanks for your help!George

author: calibrationfixture
author_rank: Regular Contributor
timestamp: June 25, 2024, 06:16:38 am
content: Hi jorgino," I did try to put it together last weekend and could not get that lvps board in for the life of me. Thanks for your help!George "Unscrew the Alu Rear (yes all screws). It don't fell off. Then you can make enough clearance to insert (or take out) the LVSMPS without making any scratch on the aluminium Frame.Success,Calibrationfixture

author: MarkL
author_rank: Unknown
timestamp: June 25, 2024, 02:50:30 pm
content: Quote from: jorgino on June 24, 2024, 11:11:01 pmYou should be able to get a good GPIB PCI interface for around $30 (like NI or HP). Beware of the name-brand GPIB USB adapters as there are many counterfeits out there and some work and some don't. There are also a number of USB GPIB projects out there, like the AR488. Search around on this forum and you'll find lots of suggestions.I have an old HP ISA GPIB card, or an RS232 to GPIB converter box (IOTECH Micro488/EX), and you can have either for postage. The ISA card is still supported on Linux if you have an ISA computer, and the 488/EX just needs an RS232 port. Either will do the job of reading out the NVRAM. PM me if interested. (You caught me in the middle of a lab clean-up.)If you just want to get on with it and not mess with GPIB, EXER 02 is also fine and what most people do since most of these scopes are not equipped with GPIB. As long as you can get a clean capture of all the values with the existing screen issue.QuoteYou'll find different opinions on this, but my advice would be to NOT start with capacitor replacement when you have prevailing and unexplained issues. Too many times I've seen people layer new problems on top of existing ones.Now, it may actually be the capacitors need replacing, but my approach would be to go through proper troubleshooting and prove they are bad first.QuoteTo be honest, I haven't ever removed my LVPS. Besides calibrationfixture's suggestion, you can also ask in the big thread where more people are probably watching.