@VisibleSignals Finally built the 1IF. Before I plug it in to test, just want to double-check that I connected the ground pins correctly (the build instructions weren’t 100% clear to me). Like this, right?..
Also, I put most of the components of the back board onto the opposite side from the labeled silkscreen. That seemed to make the most sense to me, to keep them out of the way of the power header. If that was your intended way for people to build it, might be good to mention that in the build guide, at the start. (And, indeed, might be good to label the parts on the other side of the board on any future revisions.)
Finally built the 1IF. Before I plug it in to test, just want to double-check that I connected the ground pins correctly (the build instructions weren’t 100% clear to me). Like this, right?..
Ground pin wiring is correct, well done!
Also, I put most of the components of the back board onto the opposite side from the labeled silkscreen. That seemed to make the most sense to me, to keep them out of the way of the power header. If that was your intended way for people to build it, might be good to mention that in the build guide, at the start. (And, indeed, might be good to label the parts on the other side of the board on any future revisions.)
For better or for worse (probably the latter) when I designed it I put the components on the same side as the power header, because I was worried there wouldn’t be enough room between the two boards for the components. Turns out there would have been enough room (except maybe for tall electrolytic capacitors)… but sadly it’s too late now
So, you will run into trouble with how you’ve currently done it, because the op-amp power pins are effectively reversed when the op-amp is soldered on the opposite side. You MUST move the LM6172 to the same side (rear) as the power connector before you power it up. All the other components are fine soldered on that side though. If you have powered it up already then very likely the LM6172 will have been fried and will need to be replaced. Sorry to be the bearer of bad news
This is why I should ask questions before I solder things together! But I just felt like getting something done today, haha.
Luckily, I have indeed waited to power it up. Phew.
Downside, I guess, is that moving the IC (which of course I should’ve realized is the component where side of board really matters!) to the other side is going to be a bit of a trick on such a tiny, tight board. But I’ll muddle through, I reckon.
May be worth updating the build guide to say that putting components on other side is fine for all but IC. Good to spell things out in detail for folks like me who rush in (without fully thinking things through).
And, yeah, I usually use taller (cheaper) capacitors from Tayda when they fit, but had a few of the shorter ones spec’ed in LZX designs on hand.
Oof, yeah, not having much luck getting this IC off.
Desoldering smaller components isn’t that difficult. But something with this many feet and this tight a board… Looks like I’ve screwed myself a bit here. Realistically might not have the right tools for this. 99% sure I’ve already fried the chip with the amount of heat I’ve given it trying to make this happen. Not too big a deal since I actually have a ton of LM6172s lying around. But looks like I might need to remove some of the surrounding components too and will need to first reacquire a few of the less common resistor values of which I don’t seem to have any spares.
I don’t know, unless anyone has any hot tips for desoldering ICs.
ICs can be very hard to desolder. try to heat several pins at a time (with added flux) and put some force underneath the IC to pull one side up. then continue with the other side.
If that fails:
a destructive method would be to cut off the legs, then desolder the remaining pins.
and if that fails, you can fill the holes with solder blobs and place the new lm6172 on top of that (or use a socket) and reheat the blobs .
All what matters in the end is that the pins make a good connection to the board.
doing this with a hot air station would be the best approach - if you have access to someone with one, or maybe a shared hackspace etc they likely have one already - alternatively they can be picked up for quite cheap - im still on a 30euro one i got maybe 4 years ago… just remove as much solder with braid as you can first - then hold the ic with tweezers in one hand and heat the pins of the ic with other until it just comes loose
Agreed, it’s not easy. TBH chips can take a surprising amount of heat, but yes they do have a limit.
My technique when I used to do tool-less desoldering was to run the soldering iron back and forth along well-lubed (with solder) pins on one side, while simultaneously trying to use a small flat screwdriver to lever up that side of the chip. Once it is levered nearly (but not all) the way up, swap over and do the other row of pins. Then repeat with complete pin removal, one side at a time. It’s incredibly awkward and difficult and the success is absolutely not guaranteed. It took a lot of practice.
One helpful tip I can give you is to look up “8pcs Hollow Needles Desoldering Tool IC Extraction Tool Set” or similar because they are pretty helpful in certain circumstances (especially useful when cleaning out the pin holes before you solder in a new chip).
A chip removal tool (like pliers but with little handles on each end, to lever under the chips) is a handy thing to have as well.
If you’re super-lucky your soldering iron model might support copper-block tips which can melt the solder of all DIP chip pins at once, but those are rare as hen’s teeth. I only have a DIP16 so it’s often too big for DIP8.
Your best bet is absolutely a hot air rework station, but the decent ones tend to be quite expensive On the plus side, once you have one you can recover endless components from old electronics and save! I have a very large pile of e-waste I work through on cold nights
While I’m here providing random advice, check out Peper’s Pedal’s “Rocket Sockets”. They are just the best!
And the lateral fans from really chunky old printers are great for keeping the fumes away when you’re soldering - especially if you’re harvesting components from e-waste and the solder they used smells REALLY funky :-o
