Re-soldering a PC board

Thread Starter

JulieMor

Joined Aug 29, 2012
12
A small fan strategically placed will disperse solder fumes away from your face. All you need is a slight breeze.

If you're not trying to save the IC, often you can cut all the leads close to the body then desolder one pin at a time.
Thank you! On both counts! :D

I was afraid any fan blowing over the solder would make the solder difficult to flow. Some areas of the board were almost impossible to get the solder to flow right.

As for the ICs, if I can cut the pins, I'll do that.

Thanks again!
 

flat5

Joined Nov 13, 2008
403
Do you have a cheap multimeter?
You can use the low ohms function to check for shorts (if two traces are joined by solder).
You should have such a meter if you are going to do projects like this. Prices start at $5.
 

Thread Starter

JulieMor

Joined Aug 29, 2012
12
I have a Fluke amp clamp that has Ω as one of the options. The others are VDC, VAC and amps. I think I have a cheapo Radio Shack device somewhere but I wouldn't call it a multimeter.

Yesterday I installed the re-soldered board with the blown fuses replaced. Before I connected it to anything else, I plugged in the AC cord without issue - no blown fuses. I then connected all the plug-ins to the power supply board and turned on the power switch. The red standby light lit, then the green on light lit, then the green light went off. No video, no audio.

The fuses that had blown were still fine. I even checked them with the continuity tester and I also checked the 10A fuse at the power supply.

The service manual said to check if there was a red power down (PD) light lit on the power supply board. There was. Following that it then asks if there is a PD light lit on the DEFLECTION SERVICE Assy or on the CONV. AMP Assy. The light was lit only on the CAA.

The cause of that is "V. deflection stoppage" and list seven items to check, four of which are making sure everything is plugged in tightly. The other three are "abnormality in V. BLK 2 waveform at Pin 2 in the DIGITAL CONVERGENCE Assy" then the same at Pin 6, and lastly "No waveform is output from Pin 1 of the CN902."

Everything related to testing that and the CN901, 2 and 3 relate to waveform. In the section that refers to the fuses that blew previously, it says in the part relating to the CN902 to replace IC901 and 903 which are both part # STK932-110.

I then took out the Conv. Amp Assy and replaced those two ICs with an 18 watt version, STK932-180. They are 18 pin ICs that attach to a large aluminum heat sink with machine screws. I reassembled that making sure the white paste (for heat dissipation?) was evenly spread on the back of the ICs.

I've read through the service manual and taken what I can understand. I attached some of it that relates to the troubleshooting process from the manual. It looks to me like I can keep ordering and replacing parts for quite a while but without sophisticated equipment this process will be many shots in the dark.
 

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Thread Starter

JulieMor

Joined Aug 29, 2012
12
After pulling my hair out while surfing the net for something, anything, that would provide even a ray of hope that I won't pour tons of money into this I decided to just buy a new convergence amp assembly from Pioneer. It was tough plunking down $315 but the service manual said if there was a LED lit on the convergence board, that's most likely where the problem is.

So I installed the new convergence amp assembly and turned on the TV and ... :(. No luck. I'm now returning the board but only get back $260 because Pioneer has to pay somebody to restock the thing. :eek:

What I've decided is to buy the parts and pieces the service manual says could be the problem. That venture will cost me $43. If that doesn't work, it's time to bury the monster and lick my wounds.

Wish me luck!

Thank you to everyone who helped me with this along the way. You are all very patient and kind.
 
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