There aren't too many people who can recreate unobtainium custom ICs with off-the-shelf parts. So far I got lucky and the few chips I had to do were either identical to an off-the-shelf part with a different pinout and inverted enable or had an incredibly simple function like quartz oscillator plus divide by 65536 (2^16).
Thanks! Indeed in this case, the different voltages were the biggest problem. The signal itself was fine with the CMOS chips, but it would have needed some decoupling and driver stages... so much more additional components than what I ended up with.
Thanks! I *am* working on getting at least a slightly more cusomized soundtrack... But I'd like to keep it in the same style, cause I like that very much
I was sold to the concept of RPN ever since a friend showed me his HP 25 calculator back in 1976. My HP 48GX is still my main calculaor and I have it also as an app on my smartphone. In my workshop I have an HP 35s in case some numbers have to be crunched. RPN is so efficient and I am very used to it. Using "normal" calculators with algebraic entry system gives me a hard time.
Mr Atkelar you are my new favorite an parr with this old tony or mikes electric stuff and more favorable than Mr carlsons lab. You glance over troubleshooting, but I'd like to see your process, it's most impressive! Happy new year and thank you!
Awwww... thanks for the kind words! I haven't yet found a way of capturing the troubleshooting phase in a way that would translate well to video... It's mostly "probing pins" and "thinking". In this case, I didn't dare to let the device run for any longer period; I feared overheating or overvoltage damage, so I only gave it short spurts to probe - that made it next to impossible to also hit the "screenshot" button on the scope or capture meter readings. A fully digital metering solution, where I could just record hours and then cut out the intersting values is way outside my budget I'm afraid.
@@atkelar Uh it must be hard to troubleshoot let alone to make it concise for a video... In any case, to see an upload from you will make me instantly click on it:)
Oops - quite a few typos actually. I was rather tired when uploading. I hope I fixed them all by now. (it would tie in to the "Ero r o" readout, but unintentionally 😅)
That’s awesome, I found one of these at a swap meet last year in a similar condition: no battery, no charger, and the display driver is tired out and dim… I never thought about going as far as designing a replacement though, major props for that! Would you possibly consider publishing the schematic/pcb design for that little board? I’d love to get mine fully restored too, I’d appreciate it!
I would not mind sharing it, but as it stands I think it needs a slight bit of more tweaking. The chip I used works, but it has an additional output latch gate and the simple way that I'm driving it makes for the 7seg display to show "ghost" segments one over. I need to find a better chip wihtout that gate or make that gate slightly different. I just got so many projects piled up at the moment that this little visual problem was pushed forward again and again.
Nicely done. The painting of the box seemed good. Why the retrobrighting didn't work? I love HP calculators. I have several old ones. Why in cat's hell don't you have more subscribers? Are you sure that RU-vid algorithm didn't flag you as a child's channel? Because you know you are a (pardon me for the expression) a plush cat?
Thanks! The retrobright might fail for a number of reasons... sometimes the plastic isn't the right kind, sometimes the combination of peroxyde and UV isn't "just right"... I am certainly not chemist. As far as I can tell, I am not flagged as children channel. The presentation format doesn't take away from the fact that the content is certainly not aimed at kids. I aim at the "young at heart" nerds and I do label my videos accordinlgy. As far as I'm concerend, It is fine for children to watch along, but the target audience is certainly 18+.
Hi Atkelar i was wondering if you have any suggestions on how to clean and dry circuit boards? We had a big hail storm today that smashed through the roof of my shed and has drowned my lathe and my new milling machine among other tools. I don't know much about electronics and the first person i could think of was you. Could i use contact cleaner and compressed air to dry the electronics out or is there something better? Thanks for any input ahead of time. Building a new roof Tomorow.
Sorry to hear about such damage. I hope there is some insurence? Anyhow: the circuit boards alone usually aren't much of a problem when the water is clean; I would however pay close attention to what is attached to them: Iron cores (ferrite beads, transofmer cores and the likes) are sometimes prone to rusting and bare metal might oxydize so getting the water out is prime for those. Not having any residue of cleaning agents is the second priority. I usually go with an IPA spray, as IPA evaporates without a residue. Switches and potentiometers that got wet come to mind as espcially in need of attention. While I occasionally rince a PCB in a sink, I never would do that with potentiometers or switches for the oxydation factor. Contact cleaner for switches is a good idea, and there are special ones out for potentiometers, assuming they are new enough not to have carbon paper inside, it should be safe to drown them in cleaner too. The cleaning spray I use is a bit aggressive and should be rinsed off after doing its thing, so definitely look for something potentiometer friendly that does not require flusing. If there is water left in some nooks and crannies, WD40 ("Water Displacement 40") might also be a good idea for a first run, followed up by IPA, since I'm not sure if WD leaves any residue that might affect electricity. A few spritzes and wipe down with silicone oil for any non-electronic metal parts is what I use for rust prevention, again, WD40 for removing any lingering droplets of water.
@@atkelar Thank you sooo much for getting back to me. Unfortunately i don't have insurance, but hopefully i can get some IPA and some potentiometer spray from the local electronics shop if not ebay. i have contact cleaner spray that says it leaves no residue but i will go with you're suggestion, rely can't afford to screw it up. Im a small engines mechanic so i dont have much to do with electrical, I have been watching your videos for some time now though most of it goes over my head im constantly amazed and impressed with the work you do (one clever kitty) i did some searching around but couldn't find anything relevant to my issue so i asked the only person i mean kitty that actually knows what they're doing, you. I have just finished putting a new roof on my shed today with some help from some friends i will be out of commission tomorrow/couple of days due to a blown disc in my back but when i get sorted i will let you know how it all went. Thanks again for the advice i appreciate it a lot, all fingers crossed it works out and saves my machinery. Keep up the good work cheers from Aus.
Why replace with NiCd when NiMH should work just as well in most cases with better cycle life and less heavy metals? Is there some situation where NiCd is a better choice or did you just want to stick to the original setup?
I'm not yet feeling comfortable enough to adjust the charging circuitry. For NiCd batteries, I know that a resistor in line with a "close enough" voltage is fine. And that's how most of these old devices are set up. To use other chemistry, I'd need a fitting charging cirtuit too... eventually, mabye.
@@atkelar Well, indeed it was. Only the non existant basics in electronic lessons makes it difficult to understand the single steps in the video. Beside that, there is another way of de-yellowing such an old case like this, with 2% hydrogen-peroxide liquid and a UV-lamp. Costs only a little more time than painting. 🙂👍
I did try the hydrogen-peroxide route.... (regrobright... retrobrite?) but it didn't do anything. It might be a combination of chemical yellowing and nicotine coating. But neither the peroxide nor a magic eraser changed anything on the color. I don't like painting plastics, but in this case, I think it was the best option, specifically with that huge ugly rectangle on top.
