T - amp R2 pad lifted, any way around?

[CedMan]

Hello experts? On my attempt to mod my second t-amp, I managed to lift my pad for the second time on my second t-amp, same place, on the R2 ... obviously I was very upset that it happend a second time because I managed to get it done and for some reason while I'm working on other part it's lifted ... very upsetting.

Anyone knows how I can get around that lifted pad? I've been trying to trace the pad without much success ... is there any alternative point after that that I can leverage so I don't kill my second perfectly good board?

Any help would be greatly appreciated. Thanks!

-Ced

 

[Jumpin John]

If it's an expert that you are looking for ,I'm not it, however I can offer a suggestion. Assuming that you have removed R2 as Panomaniac has suggested, the input schematic from his website seems to indicate that a connection to R5 is possible. I have managed to salvage 2 boards by connecting a lead to R1 or R2 after lifting pads on C3 and C4. I soldered directly to the end of the resistor which is less likely to be lifted because it is connected to 2 pads.

 

[TriodeGuy]

When you say you've lifted a pad on R2 I assume you mean that there is one good pad remaining.


If you look at Michael Mardis's schematic one side of R2 gets shorted to pin 15 on the tripath chip. The other side is shorted to the positive side of C4. So your first step is finding which of these the "good" pad is shorted to. Touch one of your ohm meter leads to the remaining R2 pad and then touch the other lead to one side of C4...do you read anything? If not try the other side of C4. If you read a short to either one of these sides then you know the other side must go to pin 15 of the tripath. If you don't feel comfortable soldering blue wire directly to the chip, then you could run it to one side of R5 instead. Use the ohm meter to find out which side of R5 is directly shorted to pin 15...this is the side you want to run your blue wire to.

If you didn't read a short on either side of C4 then most likely the remaining pad goes to pin 15 of the tripath but you'd be well advised to verify... Touch one lead to the remaining pad and the other to pin 15 on the tripath. IF this proves out then you need to run you blue wire to the pos side of C4. If you don't know where the pos side of C4 is just use the ohm meter to find out which side of C4 is shorted to one of L2 pads...actually one side of C4 should read a short to both sides of L2 since L2 is just a coiled piece of wire.

 

[Jumpin John]

I checked a dead board with a continuity tester and there is a connection between the right side( with the LED at the top) of R2 and the right side of R5. I can't say if you will be bypassing any circuitry by connecting to that point however. If you are connecting a lead directly to a pad such as R2, it would be helpful to hot glue the lead to some part of the board so it won't be as easy to lift the pad while working on another part. I had that happen several times before I bought my glue gun.

 

[CedMan]

Thanks!!!!

Thanks alot for the help, I managed to fix the problem by connecting to one side of the R5 ... thank god I didn't waste my second board now and I hear wonderful music coming out of my amp.

I'm going to try the same trick on my first board which had the same pad lifted, hopfully I can salvage that one as well.

Again thanks alot for the help from everyone, really appreciate it!

-Ced

 

[zanash]

There's a trick to be learnt here ...........the reason the pads are lifting is that you have either not used a solder sucker to remove all the solder from around the component to be removed or you are lifting with too much force. That said I to have lifted pads, but rather than find the next component, I took a sharp blade and removed the track overlay on a good section near the lift and scraped down to the copper track, resoldering the component lead.

 

[nbrophy]

More Lifted Pads

In my 1st attempt to do the stealth mod on my T-amp, I was not only able to lift one pad but two pads, before I figure how to properly remove the surface mount components from the PCB.


I lifted one pad C3 and C4. I investigated the T-amp schematic from Michael Mardis's page and I figure out the following:

L1 – C3 – R1 – R4
L2 – C4 – R2 – R5

I tried followed TriodeGuy’s suggestion on identify the missing short. Using my multimeter to measure the resistance from the remaining pad, I get a reading from L1 – C3 and L2 – C4. Does this mean the missing pads went to C3 – R1 and C4 – R2? I assume in order to correct my sloppy work; I need to bridge the remaining pads from C3 – R1 and C4 – R2. Is correct? Is there any specific method or wired that should be considered when bridging these?

 

[gychang]

important desoldering technique

I lifted the soldering base off of t-amp twice, and only after seeing this video, I learned how to properly desolder the SMDs.

Basically heating the each side of component about 1/2 sec, alternatively does the trick.

http://tangentsoft.net/elec/movies/tt04.html

recommend highly to prevent lifting the soldering pad.

gychang