EEVblog 1664 - REPAIR with Junk Bin Parts! Keithley 2302 - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: February 03, 2025, 08:43:06 pm
content: Repair of a Keithley 2302 battery simulator with junk bin parts. But it did put up a fight!00:00 - Faulty VFD display in a Keithley 2302 Battery Simulator01:22 - Teardown03:14 - The Display driver PCB04:30 - Solder Sucking Sucks05:26 - The VFD display module, a Newhaven Display VFM162SDAR806:50 - Probing Pro Tip07:28 - Probing the VFD signals on the oscilloscope09:42 - Searching for a replacement 16x2 VFD display15:03 - Potential replacement LCD16:38 - Identical replacement found17:44 - Lets check the junk bin...18:33 - Pinout trap for young players19:25 - First test FAIL, but hold on a second, lets try something...21:09 - Winner Winner Chicken Dinner22:12 - WOAH, now it's not working?24:09 - Lets try THIS...Part 2:

author: bdunham7
author_rank: Super Contributor
timestamp: February 03, 2025, 08:53:18 pm
content: Nice! This is the content that I think people are looking for.

author: EEVblog
author_rank: Unknown
timestamp: February 03, 2025, 10:58:06 pm
content: Quote from: bdunham7 on February 03, 2025, 08:53:18 pmI conciously added the extra bit about the probing and the probing tip, thinking that it's adding value. I probably ordinarily would have been lazy enough to not bother doing that

author: ksio89
author_rank: Contributor
timestamp: February 04, 2025, 01:16:10 pm
content: Next time my wife whines about me hoarding electronic parts and accessories, I'm gonna show her this video! Good job adapting whatever part you had available and making it work, Dave. Attempting to save cash really makes people creative, ha!

author: Smokey
author_rank: Super Contributor
timestamp: February 05, 2025, 01:58:55 am
content: Funny. I watched this video, and almost commented to check the cap on the 5V rail on the display board but since you got it working with an arguably better solution with the LCD swap I just moved on.Then I saw the follow up video. I missed my chance for a video shoutouthttps://www.eevblog.com/forum/testgear/keithley-2306-dual-battery-simulator-repair-(maybe)/msg4968169/#msg4968169Quote from: Smokey on July 18, 2023, 09:18:54 pm

author: gabiz_ro
author_rank: Regular Contributor
timestamp: February 05, 2025, 07:38:17 am
content: It might be some brightness control on menu?I see in datasheet at "Function Set" that is first command after any reset.Default values for BR0 and BR1 is 0 that means 100% brightness but maybe software set other value accessible somewhere on menu.EditI don't see anything related to menu and brightness only via SCPI commands can adjust it in 0.25 steps in interval 0-1

author: finos
author_rank: Contributor
timestamp: February 05, 2025, 10:29:24 pm
content: Bit late reply , semester exams got in the way…2 days ago, I commented on the video the followingQuoteDave kindly replied:QuoteSo, I think I should explain myself a bit better.I really liked how you went over the whole board, identified the LCD, and then approached the repair methodically in your second video.My comment was specifically about the moment after the 4-minute mark, when the VFD PCB became visible. Seeing the 14-pin header immediately signaled to me that this was the classic HD44780-compatible character LCD. My confidence was nearly 100% when I spotted the PCB markings around the 5-minute mark: RS, R/W, E, followed by DB0–DB7.When I mentioned “overthinking,” I didn’t mean the part where you found the datasheet and went through it—that’s standard practice. What I was referring to was the part where you started going through varius part aggregators, spiral out talking bus analysis with a logic analyzer, browsing multiple component aggregator sites, and almost purchasing a $60 replacement.If it were me, after seeing that display, my first instinct would’ve been to go straight to my parts bin (or junk bin), grab a similar LCD, check voltages, solder it in and if it works, move on with my day.Sorry if I sound arrogant, hasty to jump to conclusions, or too quick to assume that this interface is so widely known. That wasn’t my intentionP.S. That contrast pin is such a trap… I fall for it every time!

author: EEVblog
author_rank: Unknown
timestamp: February 06, 2025, 02:07:19 am
content: Quote from: finos on February 05, 2025, 10:29:24 pmThe difference is, my job is to potentially find and make interesting Youtube videos, yours isn't, so I might approach something a bit differently in a different order than you would. Or a different order than I ordinarily would if I wasn't shooting a video about it.I get this comment a fair bit on repair videos, why did you do it this way, why didn't you do this before that, why is this video 30min long when you should have instantly recognised X and did Y, it should have been a 5min job etc.

author: bdunham7
author_rank: Super Contributor
timestamp: February 06, 2025, 02:49:57 am
content: Quote from: finos on February 05, 2025, 10:29:24 pmThe whole point here is to learn how you deal with things you are NOT familiar with and perhaps don't have laying in your junk bin. It's certainly nice to have that tidbit of knowledge and the part at the ready (I have my own stash...) but what do you do, how do you think and where do you start when it is all new to you? And can you properly diagnose and repair an unfamiliar unit the first time, without damaging it?

author: Smokey
author_rank: Super Contributor
timestamp: February 06, 2025, 03:24:29 am
content: Quote from: bdunham7 on February 06, 2025, 02:49:57 amEquipment repair procedure, step by step..Step 1 = Measure power supply rails..Step 2 = Stare at equipment for a while.Step 3 = Ask for help on EEVBlog...Step 4 = Profit

author: reagle
author_rank: Unknown
timestamp: February 10, 2025, 02:18:20 am
content: A while back I happened to get a similar model (2304A)and ended up doing a very similar mod, plus added front panel binding posts while at it .Writeup is herehttps://kuzyatech.com/hot-rodding-a-keithley-2304a-power-supply

author: ballsystemlord
author_rank: Frequent Contributor
timestamp: February 20, 2025, 06:18:05 am
content: So, I've read all about electrolytics going bad because the electrolyte drys out, but I've never heard of a tantalum cap going bad.Can anyone direct me to more info on the subject? I did search online, but the articles I've found just talk about failures due to improper usage.Thanks!

author: thm_w
author_rank: Super Contributor
timestamp: February 20, 2025, 09:01:38 pm
content: Quote from: ballsystemlord on February 20, 2025, 06:18:05 amSecond google result:https://www.onelectrontech.com/tantalum-capacitor-failure-modes-and-causes-esr/Some discussion here as well:https://www.edaboard.com/threads/tantalum-capacitors-damage-problem.400466/popcorning if not baked:https://nepp.nasa.gov/docs/tasks/003-Evaluation-Polymer-Tantalum-Capacitors-for-Space-Applications/NEPP-CP-2021-Teverovsky-Paper-IEEE-Trans-Dev-Mat-Popcorning-Failures-Tantalum-Capacitors-20210000605.pdfThe older through hole type dave always talks about may be worse,https://www.eevblog.com/forum/beginners/tag-tantalum/Modern tantalum don't really fail any more often than high value ceramics.

author: ballsystemlord
author_rank: Frequent Contributor
timestamp: February 21, 2025, 03:17:40 am
content: Quote from: thm_w on February 20, 2025, 09:01:38 pmNot to sound ungrateful, but the second search result I already went to. It's not pertinent. Consider:1. Failure caused by high voltage of low impedance circuit. (Discuses incorrect usage of tantalum caps in a circuit with respect to maximum permissible voltage.)2. The peak output current is too large. (Discuses incorrect usage of tantalum caps in a circuit with respect to maximum permissible power dissipation.)3. Tantalum capacitor ESR is too high or AC ripple is too high. (Same as above.)4. The leakage current of the tantalum capacitor is too large, resulting in insufficient withstand voltage. (Same as #1 above.)Quote from: thm_w on February 20, 2025, 09:01:38 pmUmm, again, not really pertinent. The discussion just talks about the generics of tantalum failures pre and post-sale. They never even reach a conclusion and the OP never says what was or was not discovered (or ruled out) upon further investigation.Quote from: thm_w on February 20, 2025, 09:01:38 pmCool, but not what I was really looking for.Quote from: thm_w on February 20, 2025, 09:01:38 pmThat's good to know.What I was more interested in was EOL failures, like Dave's in the video. The instrument was working and was turned off. The electrolytic dried out, but the tantalum wouldn't have. Thinking more about it, maybe the electrolytic caused the tantalum's failure, hmm....

author: thm_w
author_rank: Super Contributor
timestamp: February 21, 2025, 09:39:25 pm
content: Overvoltage does not necessarily mean incorrect usage, it could be due to unexpected circumstances (the eletrolytic failing resulting in a high ripple voltage or ripple current for example).Tantulums will fail over time, just not the same as electrolytics where the failure rate increases as time goes on.https://www.vishay.com/docs/40292/deratantcapsdeponcathsys.pdf10uF 16V capacitor, was it 5V across it?

author: EEVblog
author_rank: Unknown
timestamp: February 21, 2025, 11:57:48 pm
content: Quote from: ballsystemlord on February 21, 2025, 03:17:40 amQuite possible. If one cap fails then it can put more stress on the cap, whether or not it's on the same side or the opposite side of the converter.

author: Smokey
author_rank: Super Contributor
timestamp: February 22, 2025, 09:42:35 am
content: Around 8:55 he shows the original VFD that had it's bad caps replaced by the previous owner.