Soldering OP amps

[nacho459]

I have mentioned before that I am in the midst of replacing all the 4558's in my console with better Op Amps.

http://www.groupdiy.com/index.php?topic=7334

In total I am going to be replacing about 250 8-dip IC's. Normally I would buy the little sockets to make everything cleaner. But no matter how cheep they are 250 of them add up in price. The curent 4558's are soldered directly to the PCB, and I'm wondering if there is any real chance of damaging the new op amps by soldering them directly to the PCB? Could the heat from the soldering iron kill 'em?

 

[CJ]

Man, that's a lot of work. I would be more worried about damaging the PC boards.

Snip the op amp leads as close to the case as possible. This should leave a little "hook" that you can put the soldering iron tip under. The leads have a tendancy to stick to this hook, by way of magnetic or electric fields, I do not know which. This makes lifting out the leads very quick and easy. Then the solder sucker, and/or the copper braid solder wick. I would get the 30 ft roll. :razz: Of couse you know all this, so I shut up.

Hopefully you won't have a ground plain sucking all the heat from your iron while you try to lift yher lead which is soldered to the plain.

You can alternate leads, start with pin 1, then solder pin 5, in a cross manner to avoid excess heat.

I would wear a wrist strap for a job this big, as the IC holes will probably not like anything over two or three IC replacements.

 

[maneco]

don´t worry about soldering the new ones directly...you won´t damage them :thumb:

 

[Gus]

I do not like sockets. As a chip heats and cools it can start to move up out of the socket over time.

 

[Butterylicious]

Mouser has 8 pin IC sockets for .06 each. That's a mere 15 clams for 250. A lot is riding on the quality of the boards and your soldering skills. I agree with everything CJ said, especially being more concerned about damaging the boards than damaging the IC's. I'd socket them myself.

 

[SonsOfThunder]

CJ's advice is spot on. I would just comment that the mechanism that holds the IC legs to the iron is solder wetting. So be sure you have a little bit on your tip before you remove those legs.

I answered the last question in that thread just now btw...

What OA did your listening tests make you decide upon??

Peace!
Charlie

 

[bcarso]

Gawd I hate desoldering things. I bought a fancy Hakko motorized-pump desoldering machine. It works about half of the time. CJ's snip and lift technique is a good one though unless they bent the leads over on the solder side.

Agree that the danger is board damage. ICs themselves are surprisingly robust. Make sure the iron is safety-ground referenced as well as the board. I've blown out CMOS by forgetting that the unit I'm working on is referenced to ~half of line voltage because of still being hooked up to a power supply that is plugged into the wall, even though the power is off, and touching things with a safety-ground-referenced iron.

Have patience. Until the IC lead is like a very loose tooth any attempts to extract it by force are apt to pull out the copper in the plated-through hole. Then you have to carefully solder the new part lead on both sides of the board. And don't even talk about four-layer...

 

[nacho459]

[quote author="SonsOfThunder"]What OA did your listening tests make you decide upon??[/quote]

NJM2068 - Didn't really hear an improvement over the 4558s

NE5532 - Something there I can't really describe just a cleaner sound

OPA 2134 - Drasticly different! really sparkly top.

I'm putting the OPA 2134 in the master modules, The NE5532 in the input modules & monitoring section, and the NJM2068 on the EQ's and aux sends.

CJ, I don't understand what you are talking about. Wouldn't I just use my solder sucker to remove the solder and free the old IC's from the PCB and then just pop the new guys in? What's all this trimming and hook thing. It's probably just me but I can't picture what you are talking about.

 

[soundguy]

dude, do yourself a favor and buya hakko 808. Yeah, they are like $150, but after you get one, its kinda like eating soup with a spoon after years of trying to do it with a fork... With one of those, you can desolder an 8 pin dip package in literally 7 or 8 seconds, dont have to cut anything and have way less heat exposure on the pads so they lift less. Id personally be WAY more concerned with lifting the pcb traces on an old board than damaging a new opamp. If you damage a new opamp, you can always get another one even if it costs money. If you damage the old pcb, its a real PITA to start repairing traces and all that.

hakko 808 is the most awesome awesome thing I bought for my bench, everyone here should have one.

dave

 

[CJ]

Nacho, if you use the solder sucker while the chip is still in the board, 7 out of 8 leads might be completely de-soldered. If you yard on the chip with a pair of needle nose, that eighth pin that is still partially attached to a trace might peel the trace off the board.

The hook thing means snipping all 8 leads at the point where they enter the chip. Since the leads are bent almost at a right angle where they enter the chip, if you clip them close enough, you can get in under this left over 90 degree bend with the iron tip.

Like this "J" only upside down.

Thanks for the "wetting" snip-it. I had been wondering for years!
:thumb:

 

[alk509]

[quote author="bcarso"]unless they bent the leads over on the solder side.[/quote]

Oh, man! That's one sick bastard who came up with that idea!

Anyway: Ignacio, I second those who urge you to get a desoldering tool. Not just a solder sucker, I mean an actual desoldering iron, desoldering station, or whatever you wanna call it... But not all desoldering tools are created equal, and there are some expensive pieces of **** out there! I have a ******-looking "El Hack-O" thing that just works the balls...

Do get one, but ask around or try before you buy. Caveat emptor!

Peace,
Al.

 

[pstamler]

[quote author="nacho459"]

NJM2068 - Didn't really hear an improvement over the 4558s

NE5532 - Something there I can't really describe just a cleaner sound

OPA 2134 - Drasticly different! really sparkly top.

I'm putting the OPA 2134 in the master modules, The NE5532 in the input modules & monitoring section, and the NJM2068 on the EQ's and aux sends.[/quote]

If you didn't hear an improvement with the NJM2068 over the 4558, perhaps you could save a lot of hassle by leaving the EQ's and aux sends until last, listening to the unit, and deciding whether you might not just leave the 4558's in place.

Peace,
Paul

 

[nacho459]

[quote author="CJ"]Nacho, if you use the solder sucker while the chip is still in the board, 7 out of 8 leads might be completely de-soldered. If you yard on the chip with a pair of needle nose, that eighth pin that is still partially attached to a trace might peel the trace off the board.

The hook thing means snipping all 8 leads at the point where they enter the chip. Since the leads are bent almost at a right angle where they enter the chip, if you clip them close enough, you can get in under this left over 90 degree bend with the iron tip.
[/quote]

Oh, OK I follow you now. I haven't really had problems with the traces coming off the board. As for the 808 thing I have something like that, that hooks up to an air compressor, but something is wrong with it, and it no longer sucks right. It's not that hard to get the old 4558s out of there.

 

[Gus]

I use the large soldapullt(brand name) and a temp control iron. The iron has a large tip installed for thermal mass. I have used this even with 4 layer PCBs.

If the board is single side or double sided you should not have any problems

There is a trick to using a soldapullt cutting out a small section for the tip to fit in allows you to apply the tip of both the iron and sucker to the pad and activate the sucker. The full tip does not allow as good a suction because as you pull the iron away to apply the tip the solder starts to cool and there is a larger air gap.


25 plus years of practice helps alot. I hardly ever change the tip from a big chistle tip. I angle it for all kinds of size soldering. I even use it for SMD stuff.

The cheap low ounce Cu board are a problem with any type of desoldering. For that type of board if I know I don't want to save the part I will cut the leads as close to the body and heat the solder side and pull the lead out the other, even then the Cu might lift.

 

[SonsOfThunder]

I gotta totally agree with Gus' comments on the SoldaPullit. The "big boy" is the one to get! I have used a Pace and a Metcal solder sucker and when they are working, they are cool, but a major hassle to maintain, in my experience.

CJ, I discovered the wetting thing while doing this and found that if the tip has just been wiped dry, the legs won't stick to the iron as well.

Flux is another thing that helps desoldering, believe it or not. I like the no-clean liquid, though I'd imagine that the no-clean pen would work well too.

:thumb: :thumb: :thumb: on the OPA2134! That's my fave. I have never listened in comparison to the 5532, side-by-side. I'd also say that it is going to depend on the circuit as to which one sounds better. Glad to hear you let your ears decide...that will make you feel much better when you pay the bill for parts!!

Happy Happy DIY!!
Charlie