Riddled TV Repair Forum

pete g · Posted: Thu Dec 03, 2009 5:04 pm Post subject: convergence ic's stk4121-2?

hi, my name is pete. i live in s. florida. iam currently working on an old sony ptv. model kpr4110, scc-643a-a. made a mistake when hooking up blue crt. result was a blown stk4121-2 ic. anyone know of a source for this chip? why must these chips be replaced (blue/red) in pairs?

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JTS1957 · Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away

Try MCM Electronics.

Would you want only one lung replaced? Laughing

Both ICs have same number of working hours.

pete g · Posted: Fri Dec 04, 2009 6:57 am Post subject: convergence ic's

i understand what your saying about both ic's having the same use time. however, the failure of the one ic was caused by me, not a normal failure.i replaced the blue ic, now the red convergence is off, and has limited movement. so it looks like replacing just one chip, causes an electrical imbalance. i changed the fluid in all 3 tubes. another problem is the left side of the screen is shaded darker than the right side. unfortunately, mcm says they don't have stk4121-2 ic.

kuhurdler · Joined: 28 Dec 2006 Posts: 2879 Location: Overland Park, KS

You might want to double check that number. I think it is a partial number.

pete g · Posted: Mon Dec 07, 2009 8:03 pm Post subject: convergence ic's

hi, i checked the number of the conv. ic and it is correct, actually the part number is written on the chip. i did find a source for this part. however my original question (why is it necessary to change both chips if only one is defective was never answered satisfactorly.

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JTS1957 · Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away

Well let's try this then...
Go ahead, take the set apart and replace the one IC and reassemble after converging.
Use the set for a month to maybe even a year, and don't go blaming me if you'll then have to go in and now replace the other one of the pair.

Why change ALL the spark plugs when you tune up a fancy sports car? Just replace the fowled ones. Especially when you have to remove many assemblies, brackets, fenders, etc. to get at them. Rolling Eyes

pete g · Posted: Tue Dec 08, 2009 8:13 am Post subject: convergence ic's

hi jts, i think what your trying to convey, and correct me if iam wrong. are you saying the electrical characteristics of the good ic change? instead of using analogies can you be more specific?

JTS1957 · Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away

I think I've posted the points I needed to make previously. Smile

kuhurdler · Joined: 28 Dec 2006 Posts: 2879 Location: Overland Park, KS

He's saying the chips need to be matched. They need to heat up at the same rate, and have the same internal resistance, or the convergence will shift throughout the heat range. The only way to ensure they are matching is to buy them from the same source, and replace them so they have the same hours of run-time. You also get the benefit of putting some good heat sink compound on BOTH chips, so they heat up at the same rate. .

Your method of replacing one might possibly work (at least initially), but it is hardly worth the small monetary amount you'll be saving compared to the significant effort to replace them again.

To put it another way, if you waste a little extra now, it's guaranteed you won't regret it.

With that said, I think comparing it to replacing spark plugs or car tires is a good analogy.