replacing as15-f chip

[gustav]

It's a Insigna 42" first had the neon/ negative display. Checked voltages at power supply, all within tolerance. Caps look good, I know, replace anyway. The T-conn likely suspect. As per Tom66, the vg reading were not sequential.
So, I wanted to try to replace the AS15-hg chip on the infamous AOU t conn. Well I desoldered the chip using a soldering iron and flux. and the middle metal square was still stuck to the pad. I guess the chip got to hot and perhaps it melted on it, or it's not that important as it maybe a ground.

Now, a replacement was put on anyway using paste and heat gun. Tried to watch the process very closely to prevent burning the chip. Pins lined up good and removed the bridging as well. First time doing this. Anyways, the screen is now white with ghost like images barely appearing. I have one chip left and was wondering if the pad should not have a metal square in the middle, and what is the best way to afix the final chip? Of course what other possibilities should I consider before buying a new t-conn? I don't own a hot air gun. btw.

I will post pics very soon and a more comprehensive description of the problem.

[kevinm34232]

Re: replacing as15-f chip

The metal square you are talking about, is it part of the old chip, or is it flush with the board? I had this happen before replacing my first of these chips, and after the 4th attempt (with the same chip), it worked. It's usually the alignment and bridged pins.

[gustav]

Re: replacing as15-f chip

The middle stayed on the board while the chip was pulled off. I went back and removed the square before putting on another chip. What was interesting, the supplier sent me some other chips with the order so I e-mailed them to find out what they were. They told me it was a mistake and are sending me a couple more of the as-15HG that I already have. Cool. But I afraid of there might be other problems with the board and will have to conclude to ordering another t-conn, which I was trying to avoid. The upside, I learned how to solder an IC chip and the benefit of using hot air. Although a heat gun was used, I can see the application of using a hot air station and paste. The trouble I can see is putting on the paste so the pins and tracks are visible for alignment and trying not to put to much on to avoid bridging. Also, if there still is a problem, I can't pinpoint if it's something else or a bad soldering job. Oh well.

[tibimakai]

Re: replacing as15-f chip

The trouble I can see is putting on the paste so the pins and tracks are visible for alignment and trying not to put to much on to avoid bridging.

This is the reason that I have used the soldering iron.
I guess we need stencils for that specific package IC.

[kevinm34232]

Re: replacing as15-f chip

Remove the IC and do it again, you will get better with practice. Just clean the board good and apply paste flux (I use the paste flux that comes with Quik Chip solder). You can still see the pins. Tack a couple corners down, make sure it's aligned and then just hit each pin with a 0.8mm tinned chisel tip solder iron around 350C. Usually if you bridge 2 pins put some more flux on it and touch the pins it should seperate. If you apply too much by accident it gets messy and have to use some solder wick.

[gustav]

Re: replacing as15-f chip

I tried it with a different chip and now I get nothing, like the board isn't attached at all, unlike the first one which had ghost-like displays with a white screen. The solder and pins look good. There is one pin that had 12v showing, but now 0v. I think the chip isn't even getting any power due to something else is causing the short. The connection is showing good voltage. So, it's somewhere in between. On the test points, I'm getting no voltages. I'm getting impatient and ordered another board today. Also, I need to invest in a good soldering iron station or iron.

The other problem is there is no sound from the speakers but only from the headphones. I have the service manual and getting a quick study on how to track down the problem. It's not that big of a deal, and it may keep me busy until the board arrives. I have already got a main board but it was the wrong size and there was sound and the same display issues, which points to the t-conn as the first suspect.

[gustav]

Re: replacing as15-f chip

Well, I ordered the t-conn from HdTVpartStore. Ordered it Wed. before late afternoon, and it was here Friday. It would have been here Thursday, but it was a holiday. Wow, that's faster than Mouser!
Anyway, the T-conn worked wonders. but I hated to shell out for a new board. Oh well. Now, for the sound. I believe it could be the R2a15112FP amplifier chip or some small component just before the chip, i.e. resistors or caps. But the headphone jack works with my computer speakers and that works fine for now. Time for some liquid carbo's

[sandaruwan]

Re: replacing as15-f chip

thanks