So I made an incredibly stupid mistake on my last order of boards, and I made the same mistake on 3 out of the 4 designs I ordered. But long story short, does anybody make a dual op-amp where the inputs are swapped on the first side? Like a standard dual op-amp pinout is like this:
(https://i.imgur.com/EeYOrp2.jpg)
But it would absolutely save my build if there was a dual op-amp with a pinout like this:
(https://i.imgur.com/H6deW2x.jpg)
Yup, swapped the inverting and non-inverting inputs of the first stage there, which makes a bit of difference. And I did it on three designs in a row. I guess I'll just have to dead-bug wire it. On my SMD board. Sometimes I know what I'm doing, I promise ::)
Depending on how many boards you ordered it may be cheaper to just fix the mistake and reorder rather than find a niche part that may be super expensive and probably not have the proper specs other than pinout.
From what I've seen though the typical dual opamp pinout is standardized and I've never seen a deviation. You could probably make a little adaptor board and order a bunch of those?
Use sockets for the IC's, and bend those pins out solder wire onto the bent pins and cross the wires into the socket.
Quote from: vigilante397 on November 08, 2019, 11:18:16 AM
I guess I'll just have to dead-bug wire it. On my SMD board. Sometimes I know what I'm doing, I promise ::)
That does sound like fun. :icon_razz:
Is the op amp surface mount?
Could you solder the chip to the board as is, then break some traces elsewhere to do the fix? Might be less delicate surgery.
Oh, and buy some black epoxy to cover your tracks. :icon_wink:
Quote from: Nitefly182 on November 08, 2019, 01:53:18 PM
Depending on how many boards you ordered it may be cheaper to just fix the mistake and reorder
I know, I only ordered 5 of each board, so I have 15 bad boards, and with shipping that would only be $25 or so to replace all of them. That's what I'll end up doing in the long run for sure, but I'll probably hack up the current board for testing to make sure this is the only mistake I made ::)
Quote from: caspercody on November 08, 2019, 01:57:33 PM
Use sockets for the IC's, and bend those pins out solder wire onto the bent pins and cross the wires into the socket.
That would absolutely work, except that I'm using SMD parts, so sockets aren't really an option.
Quote from: EBK on November 08, 2019, 01:58:21 PM
Could you solder the chip to the board as is, then break some traces elsewhere to do the fix? Might be less delicate surgery.
Oh, and buy some black epoxy to cover your tracks. :icon_wink:
Yes, that's probably what I'll end up doing. I need to go back and look at the layout to see how hard that would be. I have grey epoxy, do you think that works? I've heard black epoxy has more mojo 8)
Quote from: vigilante397 on November 08, 2019, 02:32:47 PM
I have grey epoxy, do you think that works?
Not if it is JB Weld or other steel-filled epoxy. I'd hate to see you follow through on a lark only to mess things up with conductive epoxy. :icon_wink:
You need the "special" Mil-Spec Zinc Chromate epoxy!!
(I have no idea if that is even a thing).
:)
MC
Quote from: EBK on November 08, 2019, 03:30:28 PM
Not if it is JB Weld or other steel-filled epoxy. I'd hate to see you follow through on a lark only to mess things up with conductive epoxy. :icon_wink:
Lol, that would be a hall-of-fame level blunder. Finish a circuit that sounds great, then promptly pour a blob of metal, shorting everything to everything :P
Quote from: vigilante397 on November 08, 2019, 02:32:47 PM
I know, I only ordered 5 of each board, so I have 15 bad boards, and with shipping that would only be $25 or so to replace all of them. That's what I'll end up doing in the long run for sure, but I'll probably hack up the current board for testing to make sure this is the only mistake I made ::)
I have a *large* cardboard box filled with PCBs like this...turns out I rarely need five to sort out the remaining issues with the board, so the other three finish up in the box. But there's no way around it. We call it "prototyping" and just get on with it!!...lol. It's a cost of PCB development and it's better/cheaper/quicker to accept it and move on than to spend a lot of time trying to work around some stupid error that you shouldn't have made but which is probably inevitable anyway.
Welcome to the half-baked boards club!
Tom
Quote from: ElectricDruid on November 08, 2019, 08:19:08 PM
I have a *large* cardboard box filled with PCBs like this
My wife upgraded mine to a plastic tub, I also have a couple hundred botched designs in various quantities :P This was not my first PCB mistake, and it will not be my last. I have a bin of "working" PCBs and a bin of "fancy bookmarks." I feel weird throwing them away, but my kids think they look neat, so I keep them around ;D
Also, I plan to fix this as soon as my kids are in bed so I will update how it goes. I decided the easiest way would be to leave the op-amp where it is and just lift the two legs I swapped, then I can jump wires to cross them. That way 6 pins stay where they are and I don't have to perform surgery on the board.
Nathan, were you the one who promised to make a pedal enclosure out of scrap PCBs in the Please Steal My Idea Thread? :icon_wink:
Quote from: EBK on November 08, 2019, 09:55:36 PM
Nathan, were you the one who promised to make a pedal enclosure out of scrap PCBs in the Please Steal My Idea Thread? :icon_wink:
Oh that's right, that totally was me. Completely forgot to do that. Well I have a 3-day weekend, I'll see if I can make it happen
Anyway, fixed the op-amp issue by lifting the two pins and jumping wires. It was not super fun and it isn't super pretty, but it works now, so apparently that was the only mistake I made ;D
(https://i.postimg.cc/cvqtXxMG/IMG-20191108-202731.jpg) (https://postimg.cc/cvqtXxMG)
Too bad I just threw away my botched twin valvecaster PCBs... they were really large and would have made great enclosures!!
MC
Quote from: vigilante397 on November 08, 2019, 09:50:16 PM
. . . and a bin of "fancy bookmarks." I feel weird throwing them away, but my kids think they look neat, so I keep them around ;D
Drill a hole in the corner, attach a piece of coloured twine, and use as alternative Christmas tree decorations! :icon_cool:
You can fix it!
Bend just those 2 legs up on the opamp and solder it down. Tin the legs and pads and add flux.
I'd use Kynar wire. Strip the end about 10mm then part strip about 5mm so you cut off a short piece with both ends stripped and about 5mm or less of sleeving in between. Make 2 of those. Tin & flux the ends. Solder on the wires crossed over and wash off the flux.
Quote from: bluebunny on November 09, 2019, 04:19:33 AM
Quote from: vigilante397 on November 08, 2019, 09:50:16 PM
. . . and a bin of "fancy bookmarks." I feel weird throwing them away, but my kids think they look neat, so I keep them around ;D
Drill a hole in the corner, attach a piece of coloured twine, and use as alternative Christmas tree decorations! :icon_cool:
Might make some decent wind chimes that way too.
Wait! Why are we drilling holes into a PCB that already has holes? :icon_confused:
Quote from: anotherjim on November 09, 2019, 06:54:27 AM
Bend just those 2 legs up on the opamp and solder it down. Tin the legs and pads and add flux.
Did you not see the picture a couple messages up? Literally exactly what I did :P
No I didn't see it. I thought everybody was still riffing on what to do with unusable boards.