Awful schematics you have seen - Page 1
Forum section: electronics / general

author: Circlotron
author_rank: Super Contributor
timestamp: July 05, 2015, 01:00:05 pm
content: Some people have no idea how to draw a readable schematic diagram! I found this little gem tonight - a diagram of a small motorcycle capacitor discharge ignition. I untangled and redrew just for my own satisfaction. Unbelievable....Anyway, lets see some of the prize winning efforts you have come across in your travels.

author: Macbeth
author_rank: Super Contributor
timestamp: July 05, 2015, 01:30:03 pm
content: LMFAO. My favourite is the superfluous earth connection coming from the coil body and having to be "jumped over" by the ignition, only to go through all that to meet a ground symbol.To be fair this is obviously a reverse engineering rather than a design. It's funny that the "back of a fag packet" drawing has been rendered on a PC verbatim rather than any sense being made of it though!

author: SeanB
author_rank: Super Contributor
timestamp: July 05, 2015, 01:30:51 pm
content: Drawn just as it was laid out on the board........

author: artag
author_rank: Super Contributor
timestamp: July 05, 2015, 08:51:58 pm
content: My pet hate is schematics that are drawn with too many signals joined by name instead of drawn wires. They're useless for faultfinding - they're no more than a netlist with IC labels.I guess if you're working in the schematic editor you can highlight and follow them easily enough, but when reading the document offline, it takes forever to work out where wires lead. And you're never sure how many signals are connected - when you find the name you're looking for, you don't know if there are others.I like to see the vast majority of wires connected on the schematic. It's OK to group similar wires into a buss, and a few signals that are messy to route is OK, but never just a sheet with a bunch of ICs and names on all their pins.

author: oldway
author_rank: Super Contributor
timestamp: July 05, 2015, 09:24:35 pm
content: Marconi radio on theTitanic

author: tom66
author_rank: Super Contributor
timestamp: July 05, 2015, 09:36:29 pm
content: Power supply from LCD TVhttp://www.toms-service-manuals.com/getfile.php?mode=viewpdf&req=OEM_Vestel_17PW25-4_%5BSCH%5D.pdf&mfg=OEM

author: darrylp
author_rank: Regular Contributor
timestamp: July 05, 2015, 10:10:32 pm
content: Quote from: tom66 on July 05, 2015, 09:36:29 pmYes I've had to fix two of these now, terrible schematic !The whole board is cheaply available as a replacement for under 20uk pounds hardly worth evening looking to fix it at that priceSent from my Nexus 7

author: Whales
author_rank: Super Contributor
timestamp: July 06, 2015, 11:25:14 am
content: So far we've identified the evils of messy layout and having to hunt for netnames, but what about the circuit symbols themselves? I don't mind what symbol is used as it's normally easy to work out:http://www.ludens.cl/Electron/audioamps/AAAAsmall.png(Full description)Has anyone come across some really bad symbols?

author: tom66
author_rank: Super Contributor
timestamp: July 06, 2015, 11:25:21 am
content: 'tis just a Vestel mistake. They put 35V ones on the board, but don't update the schematic. If a footprint roughly matches the correct pin out, they'll use that. They've used a dual N-ch MOSFET (with the MOSFET symbol drawn on the device) in place of an 8-pin controller IC before. Confusing, until you realise they're just lazy engineers.

author: B.B.Bubby
author_rank: Regular Contributor
timestamp: July 06, 2015, 12:04:39 pm
content: Not really schematic related but still a cluster ....Had to get this machine going, multiple earth leakage and neutral to earth faults. Would've killed for even a dodgy schematic.

author: Votality
author_rank: Contributor
timestamp: July 06, 2015, 12:07:23 pm
content: Quote from: B.B.Bubby on July 06, 2015, 12:04:39 pmLol my father in law (and brother in law) are sparkies. I think they would have some kind of spasm if i showed them that mess.

author: Whales
author_rank: Super Contributor
timestamp: July 06, 2015, 12:25:27 pm
content: I'm sorry, I'm going to rewire EVERYTHING and there is nothing you can do to stop me. Please pick up some cable ties on the way back, OR ELSE.

author: Jeroen3
author_rank: Super Contributor
timestamp: July 06, 2015, 12:28:50 pm
content: The blue wire in the bottom left corner is loose.Solved.

author: B.B.Bubby
author_rank: Regular Contributor
timestamp: July 06, 2015, 12:31:51 pm
content: Quote from: Whales on July 06, 2015, 12:25:27 pmI gave them a rewire quote, but I was in a foreign country, their sparky hooked it up - out of my hands.I did check and we don't have an extradition treaty with this place. O0

author: B.B.Bubby
author_rank: Regular Contributor
timestamp: July 06, 2015, 12:32:32 pm
content: Quote from: Jeroen3 on July 06, 2015, 12:28:50 pmdisconnected neutral by me for fault finding

author: TheWelly888
author_rank: Frequent Contributor
timestamp: July 06, 2015, 12:36:05 pm
content: Quote from: oldway on July 05, 2015, 09:24:35 pmThat was in the early days of electronics when there were probably no internationally agreed circuit symbols - hardly awful for it's time.

author: John Coloccia
author_rank: Super Contributor
timestamp: July 06, 2015, 12:54:20 pm
content: Quote from: TheWelly888 on July 06, 2015, 12:36:05 pmI wouldn't necessarily call that a schematic, just like PCB artwork isn't a schematic. I think that's just the wiring diagram.

author: SeanB
author_rank: Super Contributor
timestamp: July 06, 2015, 06:23:56 pm
content: Love the way they removed all the octal timers, and wired in new ones somewhere in the mess. As well the small panel mount toggle switch dangling in mid air by the inverter, most likely to get it running for some reason if you want to do some work without the whole machine running. One at work looked like that till I rewired partly, getting all the knitting mostly behind the panel out of sight. I got around a dozen totally unused relays out that were sitting there doing nothing. Added an inverter as well, and even got a power transformer out that was duplicated by another which had unused secondaries.At least you can tell the version of a revision, just by the colour of the roll of wire they used. I am going to take a bet half of your earth faults were in external cartridge heater elements outside in the extruder body. At least 3 different generations of ABB contactors in there, and a whole catalogue of other manufacturers as well replacing the failed ones. Oldest one middle row second from left, probably dated from the late 1970's.I could get contact kits and core kits for them until the mid 2000's, but they are all finished now, so I have to replace them as they slowly wear out mechanically.

author: Neilm
author_rank: Super Contributor
timestamp: July 06, 2015, 07:16:23 pm
content: The worst I have ever seen had all the interconnections (well, the majority at least) connected by net names. These were just numbers - no easy way of identifying what these signals are. Imagine a 5 digit number on every net and having to find one particular net on a 100 pin device.

author: artag
author_rank: Super Contributor
timestamp: July 06, 2015, 11:00:06 pm
content: Quote from: Whales on July 06, 2015, 11:25:14 amThat's lovely !

author: free_electron
author_rank: Super Contributor
timestamp: July 06, 2015, 11:24:49 pm
content: Quote from: Whales on July 06, 2015, 11:25:14 amapart from the non standard symbols, that schematic is actually drawn correctly and clean.there is a reason we use standard symbols.it would be very problematic if everone invented his own symbols for operators like addition and subtraction ... that's why we have schematic symbol standards too