Op Amp Guru's?

[NickC]

I got ripped off on a dbx compressor. I bought it used and didn't install it for a couple months. Seller was long gone by then. When it didn't work, I opened it up and discovered a burnt 5532D op amp.

dbx wants $130 to fix it. More than I paid for it. More than I can buy a used replacement for.

Those chips are small, eight prong, jobbies. I can easily remove the output section board (where the burned chip is) to get underneath. But I'm worried my soldering skills may not be up to the challenge with such small devices. There doesn't appear to be much space to heat-sink the prongs while soldering.

Any experience here? Should I not mess with it, and have dbx do it (I'm sure they'll do a board swap). Write it off as a lesson learned? Or is this repair achievable for a "bull in a china shop" kind of guy like me?

Thanks in advance for any advice.

[cbass]

Maybe installing a socket would work well.

[Bob S]

Let loose the bull says I.

[NickC]

Maybe installing a socket would work well.

I removed the board a few minutes ago. It appears to be a multi-layer, sandwiched board. The op amp chips are not socketed, and the prongs do not go all the way through the board. I'd have to effect the repair from the top side.

Yes, a socket would be a good thing. I'll investigate that. Thanks!

[John_P_WI]

Hi Nick,

If the DIP 8 package does not have "legs" that go through the board it is a surface mount package. That in itself is not a problem, just a little more finesse, flux and skill is required as you don't want to lift the pads off of the pcb when "flipping" the chip.

A larger concern would be "why did the op amp blow"? There may be some other problem with the power supply / voltage regulator / and rail(s). Just my 2 cents...

[NickC]

Let loose the bull says I.

On the strength of that recommendation I ordered four JRC 5532D chips. Keep in mind, only one is burned out. But the "bull" in me said "Better get a bunch of 'em".

[NickC]

Hi Nick,

If the DIP 8 package does not have "legs" that go through the board it is a surface mount package. That in itself is not a problem, just a little more finesse, flux and skill is required as you don't want to lift the pads off of the pcb when "flipping" the chip.

A larger concern would be "why did the op amp blow"? There may be some other problem with the power supply / voltage regulator / and rail(s). Just my 2 cents...

Excellent point! There are three easily accessible test points labeled exiting the PS board, +15, neutral, -15. I'll meter the power supply and see what's going on there. Thanks!

[eniam rognab]

to make removal far easier, clip all the legs as close to the circuit board as you can, no point in keeping the burned component intact. took me a while to figure this out

[vibratoking]

Hi Nick,

If the DIP 8 package does not have "legs" that go through the board it is a surface mount package. That in itself is not a problem, just a little more finesse, flux and skill is required as you don't want to lift the pads off of the pcb when "flipping" the chip.

A larger concern would be "why did the op amp blow"? There may be some other problem with the power supply / voltage regulator / and rail(s). Just my 2 cents...

Excellent point! There are three easily accessible test points labeled exiting the PS board, +15, neutral, -15. I'll meter the power supply and see what's going on there. Thanks!

Clipping the leads for removal is a good idea. Solder braid/wick to clean up the surface mount pads. No need for a heatsink when soldering. Tip should be about the same size as the pad. Get in and get out with the iron and you should have no heat problem. It should only take a second or two to solder each pin. Usually about 650F or so on the iron temperature.

I would remove the part and then probe the connections at the pad with the power on and power off. Power on to check that the supply and ground are at the right pads and not at the wrong pads. Power off to check component connections and values where you can. This should keep you from blowing new opamps and also give you a sanity check.

[John_P_WI]

VK and Bangor are spot on, add a little flux to the pads before soldering and use the thinnest diameter solder that you have.

We have young production gals (30's) that can flip a chip with bare eyes faster than I can even get the board aligned and in focus under a Mantis....

[Leo_Gnardo]

to make removal far easier, clip all the legs as close to the circuit board as you can, no point in keeping the burned component intact. took me a while to figure this out

Is the op amp the usual size DIP? If so then yes, clip it out with sharp pointed cutters.

One fine day I was shocked to witness Bob Bradshaw do the 'clip'. Unless you have the time and a good angle to the back of the board it is the way to go. If it's good enough for Bob it's good enough for me. Also, no worry about disrupting plated-thru-hole connections. Set a socket atop the lands & carefully solder into place with pencil-point iron & eutectic solder. Good lighting and magnifying lens will help. Hope you get 'er working, I like DBX gear.

[eniam rognab]

at work, as soon as i identify a bad component out come the clippers! then suck out the remaining lead and solder in one pop, easy peasey. and flux, oh yeah love that smell

good luck Nick!

[NickC]

Thanks VK, Bangor, Leo and John!

I clipped out the bad op amp chip. It crumbled in the process.

Cleaned up the solder pads with some solder wick.

Measured the rails: +15V and -14.8V.

Waiting on arrival of some fresh 5532D chips next week.

It's going to be tricky soldering the chip in place. I'll need to source a magnifying lens I can clamp on the workbench to see what I'm doing.

I have a needle point iron tip for the Hakko to install in the meantime.

If nothing else, this will be a good learning experience. Even if it goes badly, it will serve to explain why techs don't do component level repairs on PCBs anymore. Fools rush in where heroes fear to tread.

[Aurora]

Tack some solder to two diagonal pins, - it will help fix the chip in lace before you solder the rest. Just don't rush it......

[Cliff Schecht]

Dang you already ordered those crappy 5532's huh? They're decent op amps but for a few bucks you can dramatically improve the performance with a higher quality Burr-Brown part. I'd have to study the schematic a bit to find an appropriate replacement (or Google around, I'm sure others have done so) but I usually will upgrade op amps if I'm already inside a piece of gear.

The trick is not throwing in whatever op amp but finding a part that will work appropriately in the circuit you're using. If the circuit involves a unity-gain follower, for example then you'll want to use a part that is guaranteed stable when connected as a UGF.