device that is full of op-amps - Page 1
Forum section: electronics / repair

author: M6YRU
author_rank: Contributor
timestamp: April 24, 2019, 12:14:47 pm
content: hi folks, need some help...i got 3 devices, now only 1 works, here is the story...each device has a main board an a "wired connection" board that is attached by ribbon cable, the device measures fluid levels and tempreture levels.i "must have " shorted out something on the wired connection board and since then the device dont register fluid correctly and creates a thermal overload then a tempreture error... this board has 1 op-amp and the main board as a handful of them...i connected the "wired connection board" to another main board thinking it has less that could be wrong with it as its only got a couple of chips, now both main boards dont work!as the problem is with values of measurement im going to assume its one of these thats causing the problems, 1, power rail to some op-amps missing, 2,faulty op-amp, or 3, damaged processor...if i was to use diode mode and note down the readings on the good board, could this damage the op-amps? if i had something to compare reading from a working vs non-working i'd have a better idea where to start to fault find...i tried the manufacter, they just ignored my request for help of a schematic diagram even though its way too old of a device for them, sadly my guess is that its because its a security device..pictures, chip markings etc can be uploaded, i dont know what other information someone may be in need of...many thanks Ian

author: madires
author_rank: Super Contributor
timestamp: April 24, 2019, 01:15:22 pm
content: Yep, images of all boards would be the next best thing to get an idea about that circuit. The current of the DMM's diode check is limited to 1mA in most cases. So the diode check shouldn't be able to damage any component. Please start by measuring the voltages of the power rails. If you have a lab PSU you could check the bad connection board stand-alone later on.

author: M6YRU
author_rank: Contributor
timestamp: April 24, 2019, 05:43:28 pm
content: I tried to upload pictures but didnt work* here is my folder in google drive of the pictures*https://drive.google.com/open?id=1XTYYsrsePgVrlpRE6FD14ukw96TeBH98

author: M6YRU
author_rank: Contributor
timestamp: April 24, 2019, 05:49:45 pm
content: Quote from: madires on April 24, 2019, 01:15:22 pmI thought the same but as iI have never used op-amps i dont know how well they are diode mode so i thought to ask here firstI agree with finding the power rail to these op-amps, however when i check the working board i want to do a load of tests, just the units are bulky and there is many screws to remove to get to the board lol.my previous post is a link to my folder of pictures on google drive, plenty of close-up of the different chips

author: mariush
author_rank: Super Contributor
timestamp: April 24, 2019, 05:50:32 pm
content: If it doesn't work it's most likely because of thisAllowed file types: doc, gif, jpg, jpeg, pdf, png, txt, zip, tar, c, h, hex, bas, xls, odt, asm, wav, aiff, wma, mp3, flac, asc, ods, xlsx, pyRestrictions:25 per post,maximum total size 2000KB, maximumindividual size 1000KBresize each picture to 1000 ..1600 pixels on the wide side, use JPG 70...85% quality and each image will be 100..500 KB ..so you'll be able to attach up to 2 MB worth of images.Also your link is to only one imageand it's not opamp ... were you not even curious to google the text on chip?74hc4094https://assets.nexperia.com/documents/data-sheet/74HC_HCT4094.pdf74HC4094; 74HCT40948-stage shift-and-store bus registerThis is basic generic chip made by multiple companies.

author: M6YRU
author_rank: Contributor
timestamp: April 24, 2019, 06:04:35 pm
content: i did have an issue with my laptop, i noticed not long after my reply when i clicked the link it didnt go to the folder but directly to a close-up of one of the chips onboard, it was sorted promptly but anyone who clicked at the time will need to refresh to get the correct linkQuote from: blueskull on April 24, 2019, 05:51:58 pm

author: M6YRU
author_rank: Contributor
timestamp: April 24, 2019, 06:16:51 pm
content: Quote from: mariush on April 24, 2019, 05:50:32 pmthe link went to a file not to the folder with all the pictures in, it has been corrected, there is op-amps and other chips too even regulators etc etc...i dont know how to make my jpg that small? the smallest my camera will take a photo would bejust over 3.5MB even my phone dont go below 2MB lol

author: Kleinstein
author_rank: Super Contributor
timestamp: April 24, 2019, 06:33:08 pm
content: The circuit contains quite a lot of parts - not many OPs though.For a sceen filling picture it only needs some 200-400 KB in JPEG format. Quite often the resolution of the pictures can be reduced by at least a factor of 2 in x and y direction. One may need to use some image manipulation SW.

author: Gyro
author_rank: Super Contributor
timestamp: April 24, 2019, 07:18:28 pm
content: Quote from: M6YRU on April 24, 2019, 06:16:51 pmhttps://www.eevblog.com/forum/beginners/apologies-for-wasting-bandwidth/msg2153827/#msg215382725% usually yields acceptably small, readable images in Resize.

author: M6YRU
author_rank: Contributor
timestamp: April 24, 2019, 11:24:06 pm
content: Quote from: Kleinstein on April 24, 2019, 06:33:08 pmWell i learned something today, i will explain below...the little board that is a hard wired connection board has 3 chips, this board is what i swapped on to a working board that was then made faulty...the 4 chips on this board is the,78l05A a voltage regulatorLM339A A voltage comparatorULN2003A 7 package darlington array74hc4094 a shift bus registerright, as i had "a rest/break" from this thing in febuary and didnt write down any notes, the thing i learned tonight was dont trust my memory... where on earth did i see the board with many op-amps thats got stuck in my head lol i got too many projects on the go, i think i should change the title now lolsorry for what seems to be wrong info, sigh... i did google the parts but that was back in january and febuary but with so much going on with different projects and fixes and life, my head is all over the place... my brain needs a reset pin lolQuote from: Gyro on April 24, 2019, 07:18:28 pmhi five thanks for the link... the pictures in my google drive are small vs what i normally take

author: M6YRU
author_rank: Contributor
timestamp: April 25, 2019, 04:33:18 am
content: after checking all chips got power (which was a pain with old oxidised solder) they have power going to their vcc...right after having a quick look under better light most of the tracks that go to the "hard wired board" goes to these 3 chips, im wondering if its one or more of these chips that are messed up..http://www.ti.com/lit/ds/symlink/sn74hc165.pdfpic included, found i can take a picture on my phone then screen shot it then crop it to be a small pic lolthere is also an op-amp right next to the connector but im not sure if its going to it or not..has anyone used these chips? are they easy to damage, its now 5:30am so bed time is calling for me lol night all, thank you all so far for the help

author: vk6zgo
author_rank: Super Contributor
timestamp: April 25, 2019, 04:46:04 am
content: Quote from: madires on April 24, 2019, 01:15:22 pmThe diode check won't hurt, but it probably won't do much, either, as if there are any other semiconductor junctions, it will turn them on & "muddy the waters".Use the Ohms range---- if you have killed one of the Op amp inputs, it may well appear as a "high-ish" resistance to earth/common or supply, which the diode check will probably see as an open circuit.If you have one good board, compare it to the other ones.It is unlikely that the fault will not cause a difference .