More SMD nuisances

[Randall]

I am working on a small Peavey powered mixer. Among other things, Peavey suggests replacing a SMD capacitor with a different value from the schematic, IF it hasn't already been upgraded. Since it is located underneath the board, it must be lifted along with a few heat greased parts, making for a messy job. Once I got the board up and over, I found the cap, but in no way can I tell from looking at it what value it is. Now, I must say my eyesight is pretty bad these days, but even with reading glasses, magnifying headband and holding a magnifying glass I cannot see how to ID it. SO, I will replace it to be sure. What a pain, I do not like dealing with this SMD stuff at all. I ordered a few in case I burn it up or something.

Is this just the way things are now, or am I missing something? Heck I pulled it off to look again in better light, and it got away from me and now I can't find it! darn SMD world!

[nosaj]

I am working on a small Peavey powered mixer. Among other things, Peavey suggests replacing a SMD capacitor with a different value from the schematic, IF it hasn't already been upgraded. Since it is located underneath the board, it must be lifted along with a few heat greased parts, making for a messy job. Once I got the board up and over, I found the cap, but in no way can I tell from looking at it what value it is. Now, I must say my eyesight is pretty bad these days, but even with reading glasses, magnifying headband and holding a magnifying glass I cannot see how to ID it. SO, I will replace it to be sure. What a pain, I do not like dealing with this SMD stuff at all. I ordered a few in case I burn it up or something.

Is this just the way things are now, or am I missing something? Heck I pulled it off to look again in better light, and it got away from me and now I can't find it! darn SMD world!

Yeah I was checking a RF power transsistor in a ham radio and it has a few SMD caps wround you have to lift and dang it if one of them did jump in to nowhere land when I was trying to set it. It couldn't have been more than a half a mm square. I don't like them either but I won't let it dictate what I want to tackle. These are puzzles I like.
nosaj

[drewl]

Luckily we have tons of SMD parts at work.

Reels of thousands of caps.
Still a PIA to work with.

Sometimes you have to remove all the surrounding parts to replace chips.

[The Dude]

......Sometimes you have to remove all the surrounding parts to replace chips.

That's one of the suckiest parts. It makes an already PITA job even more of a PITA.

[g1]

I recently had a comp. pedal and no proper schematic but knew it to be like an orange squeezer with frills. I kind of narrowed it down to one of the Fets. Being SMD, the fet was smaller than a grain of rice.
Got a few just in case and it didn't solve the problem. Wasted a lot of time looking for the 'real' problem since I didn't have the schematic and figured I had guessed wrong.
Sure enough many days later I broke out a magnifier to use along with my magnification lenses so I could actually see the code. Turns out they sent me some zeners.
Got the right Fet and it worked straight off.

[mozz]

We were making prototype boards once for a show. Someone built one and it didn't work. Surface mount chip was soldered on backwards. 28 pins. Engineer comes over and says he built that one. Gets a utility knife, puts in a new blade, cut all the pins next to the body in 1 swipe for each side. The little legs are easier to remove, cleaned the board, soldered in a new chip correctly, presto.

[Dave H]

Engineer comes over and says he built that one. Gets a utility knife, puts in a new blade, cut all the pins next to the body in 1 swipe for each side.

When I try that trick I always end up lifting a few pads off the board. I had more luck with a heat gun. Heat the IC until you can tap it sideways then lift it off.

When soldering grain of sand SM components I line them up in order so I can grab them with tiny tweezers. One day I sneezed and never saw them again.

[The Dude]

I wouldn't try this or recommend someone else try it either, but I was at a trade show once and watched a guy remove an SMD IC with a Weller solder GUN! He'd obviously had a lot of practice. He blobbed all the pins with solder, heated the chip and removed it. Fluxed up the area. More heat to clean up the solder mess and get solder on the pads only. Then, installed the new chip. It was quite amazing to watch, but everything looked clean and it worked. Kind of like using a 10 lb sledge hammer to install finishing nails.

[olddawg]

Chip Quik is your friend! I used to do that crap with a binocular microscope and a dissection probe.

[drewl]

You get better at it.
We have solder stations with various chip sized attachments that heat the pins then uses vacuum to lift it.

[Jazz P Bass]

I found the cap, but in no way can I tell from looking at it what value it is. Now, I must say my eyesight is pretty bad these days, but even with reading glasses, magnifying headband and holding a magnifying glass I cannot see how to ID it.

Is this just the way things are now, or am I missing something? Heck I pulled it off to look again in better light, and it got away from me and now I can't find it! darn SMD world!

Somewhere along the SMD line it was decided to NOT mark the capacitors.
No color code, no number.
Nada, Zip.

Thanks!

[DrGonz78]

I swear once an SMD component hits the ground it vaporizes into the abyss. Oh there it is!! Oh wait that is a tiny piece of plastic fragment.

[J M Fahey]

My logic is:
* SMD parts=ultra high speed robot assembly
* ultra high speed robot assembly=very complex very low cost stuff

* very complex very low cost stuff=I will spend a lot of time and "they" donīt want to pay more than replacement cost, so:
* I donīt even *look* at SMT based boards, but suggest replacement.
* which may be board replacement or full item replacement, I donīt care, not my problem.

But ... but .... then you are losing Jobs!!!!!!

........ you call that "a Job"?????? Working at loss just to "do something"????


I have an agreement with God: he wonīt build or repair amplifiers, I will not do Miracles.
That includes repairing SMT boards at component level, in case you didnīt notice whatīs my point.

[olddawg]

When the boards became over 3 layers.. I gave up.. too many variables and my vision was going. That and “ball solder arrays” and using ovens. Some boards I had to send back to JVC to be x-rayed. Then the replacement boards had incompatible production run changes. This was 16 years ago... probably all disposable now.

[mhuss]

I agree with 'pitch the old board and get a new one" for repairs. Too much time and effort.

However, there are some newer chips that are /only/ available as SMD. There is a switching power controller in an up-booster I built to create 200v from a 24vdc supply, and there was literally no other option. I think R.G. posted a trial HV limiter (for adjustable B+) that has an SMD chip for the same reason.