itzza427

Well I was doing the dark HVAC display fix and found out that if you touch one end of the chip with the soldering iron and it is the opposite side that is loose,,the chip will scoot out making it difficult to reposition and solder!! For me this was just the beginning of my problems. Trying to use the tool that came with the iron to hold down the chip after repositioning,,the tip slipped and the chip took off like the old game of tidily winks(old timers will remember that one).I was doing this in my old workshop(which isn't exactly tidy)and finally gave up for tonight looking for that itty bitty chip. Will resume search tomorrow afternoon. I'm screwed if I can't find it!
I'd suggest using a eraser tipped pencil to hold them down when you heat it . Learned it the hard way,,hope I haven't ruined my display circuit board!!

Vetteman Jack

Best of luck to you in not only finding the chip, but in getting it resoldered and back to working again.

VPP

Oh no!!!

Sorry you found out about that in such a miserable way

I managed to slip one of those chips almost completely off the board while applying heat when I did the fix a few days ago. I ended up using tweezers to hold that little sucker in place while I soldered it back to its original position.

Really glad I didn't end up playing tiddly winks! Good luck with your search for the missing chip... fingers crossed it's an easy find during your next attempt

--
VPP

PNW Vett

I most definitely feel your pain with this issue. When I did mine a couple of months ago I was amazed just how small those chips were when I got to them. I had a couple come off while I was soldering them too. One went all the way to the floor in my shop and it took forever to find it. I guess my eye sight is not what it used to be now that I am 52. I ended up using the smallest soldering tip and a lighted magnifying glass to get the job done. I was really happy to see that everything worked well when I got it back in the car. Good luck with yours!

Oh 2 Fun

Hmmmm....mine is out too.....

ABSFixer is looking pretty promising right now given what you've posted

itzza427

Thanks guys,,it REALLY is an easy fix,,just have to keep those little buggers in place while you heat them!!

mcgilles

All is not lost if you can't find the missing resistor, you don't have to buy a new HVAC. They're just SMD resitors, you can buy them from mouser or digikey.
I'm pretty sure they are 6332's, measure the length of one, it should be about 6.3mm long.
the numbers on top tell you the resistance, but its coded. Write down the numbers and replace the last one with that many 0's, 103 = 10000 or 10k ohms for example. I think they are all the same? Order a replacement if the missing one doesn't show up!
Good luck!

Mastertvtech

If you get in a jam, you can pm me the size and value....I have hundreds of scrap pcb's laying around that I can surely find what you need.

itzza427

Thanks guys,,might have to go one of these routes. Cleared most of the work bench(and it is 6ft.long) and have searched about 1/2 the floor area that has some old parts and oil dry so it's a slow dirty go.WAS hoping to have it ready to tool for Saturday Fun Fest. May have to slap it together for the trip and finish later. P.S. the chips have 241 on top.any one know ohm that is??

damilleniumboy

Sir, when I did my HVAC display fix I just used a flat blade screw driver to hold down the chip. I put some solder on the soldering iron, put the flat head screw driver on the chip to make a "down" pressure, applied the solder, blew on it to cool it down, and I repeated on the other side. It works like a charm, and no special tools needed.

Mastertvtech

That should be 240 Ohms.....The physical dimensions are very important as they come in many sizes from grain of sand to 1/4"....

itzza427

That should work fine too. I just got the idea that a rubber pencil eraser tip would be a little less prone to slip as I do not have the most steady hands! I too used the little dab of solder on the iron tip,,just got caught off guard when the chip scooted in the first place. Didn't stop to think that an end had to be loose in the first place to cause the problem and that inadvertently hitting the "good end" first would let it shift duh! Live and learn,,,now I just have to find (or replace) that little bugger!

nascar57

I have a curved tip pair of hemostats that I position the tip on the resistor and weight it down with a small bag of lead weights I use for scuba diving! Works every time.

DanSavage

If you're heating up the resister enough to cause the solder on the other end to melt, you're holding the iron on there way too long.

Most people are taught to heat the joint so it is hot enough to melt the solder. The problem with that method is that you have to get the joint up the melting temperature of solder which takes a (fairly) long time.

I have a different method of soldering that I've been using for years.

First, you need rosin core solder.

Next, you touch the iron to the piece, and then touch a little bit of solder to the iron where it's touching the solder joint.

This will cause a little bubble of solder to form.

Keep the iron in place only long enough so the bubble of solder flattens out. (about 5-10 seconds)

Using my method the iron heats the solder and the solder heats the joint. This works because the solder has greater surface area which heats the entire joint more quickly than the soldering iron alone.

I just did the HVAC repair on my vette and it only took about 5-10 seconds per solder joint.

I didn't have to do anything to keep the resisters from slipping off the circuit board because I never got the resisters hot enough to melt the solder off the other end.

mcgilles

I think you just got lucky. The reason why the dim display occurs is that the solder joints on the resistors fail. If you start to repair them and reflow the solder on the one good joint while the other one has already come loose, the resistor may fall off. In that case its not a matter of poor technique, its just an effect of the type of failure. You can try to insepct to see where the broken joints are, but its easier to just reflow all of them. I prefer the reflow method when working with SMD components whether it be rework or a new installation.
on the topic of good soldering techniques, you really should clean the solder flux off the boards before putting it back together. Flux can be corrosive and over time and may degrade the solder joint if it is not cleaned. There are water soluable fluxes that can be cleaned with water, or alcohol or acetone can clean it. It may make the difference between a solder that lasts 5 years and one that lasts 50 years.

3sACROWD

To avoid the very problem th OP stated, I enlisted an assistant to hold the chip while I did the soldering. Some days my hands shake so having an extra set really helps. Besides, the actual solder repair only takes a minute or two. Not long enough to exceed the shortest of attention spans.

itzza427

Yeah,,it was just an unlucky choice of chip end! iron tip was at full temp,just touched the one end and zip it scooted. Wasn't in contact for a full second,,the OTHER end had the bad connection(basically no connection) and instantly slipped.I already had a light coating of solder on the tip,just should have had the chip held down! I'm STILL looking for the damned thing!!