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Discussion Starter · #1 ·
I just replaced the convergence chips in my JVC AV56WP74 TV and am running into a problem. I replaced the stock chips with a pair of Sanyo STK394-160 chips and am pretty confident in my solder connections. But when I powered up the TV the convergence wasn't as bad as before, but still out of wack. Also the top and bottom of the screen are pulling in towards the middle of the screen leaving a black area at centers of both the top and bottom. Any thoughts? Is it possible that I've got to get into the service mode of this set to solve this?
 

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There are reports that these chips will not work in the JVCs, but I have done several in this model now and had no problems. Can you adjust the convergence at all?
 

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Discussion Starter · #3 ·
I can run the auto convergence (didn't fix the problems), but when I choose manual convergence nothing seems to be moving when I press any arrows on the remote. Also what could now be causing the screen to pull in like this now?
 

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If you can't adust anything, and it is pulled in from the sides, you have no convergence correction. Check that you have power to the IC (both + & -) and that you have all the connections made.
 

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Discussion Starter · #5 ·
All connections look secure. And during the auto convergence, it seems to move the different colors around in super focus. But again during manual it doesn't look like any can be moved. What else should I be looking for? I didn't change any of the resistors could this be my problem? And where can I test for power on the convergence board and is this safe to do with the front off?
 

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You should be checking the basics, i.e. power to the chips, correction waveforms from the DCU, resistors, cables all connected, etc. One cannot tell you exactly what to do to fix an unknown problem.
 

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Discussion Starter · #7 ·
You should be checking the basics, i.e. power to the chips, correction waveforms from the DCU, resistors, cables all connected, etc. One cannot tell you exactly what to do to fix an unknown problem.
I really appreciate all the help.

I'll be running a more thorough test tomorrow on the board. Can I test the resistors now that the chips are in?
 

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Discussion Starter · #8 ·
Can I change resistors now that the chips are in? And if the resistors are bad, does that also mean the new chips are as well? And again any way of testing these with the chips in?
 

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You can, but it is best to do so with the yokes and ICs out of the circuit.
 

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Discussion Starter · #10 ·
Alright, I pulled the resistor at the R850 position

r850 2.2 1wmfr blue

Would radioshack carry a like resistor that I can use in place. I looked on the site and didn't see anything.
 

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Radio Shack does not have a very extensive selection of these kinds of parts. I do not keep up with their inventory. There are a number of vendors in the vendor listing, in the parts post of the convergence repair sticky, and in the sticky in the DIY Repair forum that are recommended for this kind of part.
 

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Discussion Starter · #12 · (Edited)
Ordered a pack of resistors off parts express. Replaced the burnt resistor.... Still not converging :(. Since the resistor was bad before I put the new chips in, is it possible the new chips are now bad (any way to test them)?
 

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Yes, if you installed the chips with an open resistor you likely blew one. There is no way to test them except changeing them for a known good chip.

Why Parts Express? They may be a great supplier for most things but this is not an area or their primary expertise. Lots of otherwise good suppliers have been burned with bad STKs. There are several very good recommended suppliers given in the convergence repair sticky. With the prevalence of second rate parts, it makes no sense to go to other suppliers. Buying from the right supplier and checking the resistors are two of the most important things to do to keep from having problems with these repairs. Read, then re-read, the first ten posts below very carefully.

http://www.hometheatershack.com/for.../5600-crt-based-rptv-convergence-repairs.html
 

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Discussion Starter · #15 ·
Sorry I was beat when I got home from work last night and mistyped what I had gotten from Partsexpress. I had actually ordered the new resistor from them not the chips themselves THESE. I've got a warranty on the chips though so I will be sending them back and giving it another shot with the new resistor in prior to powering up the set with new chips in place as well.

Thanks again for all the help lcaillo
 

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2.2 ohm 1 watt "power" resistor- I usually go ahead and use at least a 2 watt rated 1%-5% tolerance quality resistor when I am replacing opens or suspects. Try a company like Digi-Key or others online to get everything from one source at OEM spec or better. Its well worth the little extra cost and slight delay.
 

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DigiKey is great for many parts but not for Japanese semiconductors like the STK chips. A good one-source alternative would be B&D.
 

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I do not recommend them for semiconductors.
 

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JVC or any other TV that has stk 392-110 ICs will not work correctly with stk 394-160 or 180 ICs unless you re-design the circuit and use different value low-ohm resistors. (as in Hitachi supplied kits)

It is an urban myth that 160 or 180 ICs are better, new and improved, etc. They have different electrical characteristics than 110 ICs, such as "idle current" and "junction resistance". The 160 or 180 IC may work for a short time, but resistors will open and TV shut down from over current situation or functions will not adjust.

These "new and improved" ICs are sold on the internet to unsuspecting consumers for DIY repairs. Other problems are created by users that replace ICs and do not have a successful initial result. They adjust everything that can be accessed or remove and check resistors, etc. It is very common to have more than one fault to repair with convergence failure.

The conductive foil on the JVC convergence boards can be easily damaged from multiple solder and unsolder actions. Many users that replace 110 ICs with 160 or 180 ICs end up scrapping their TVs.

Find competent help or you will never use the TV again.

A TV technician typically has an understanding of electronics in general and the convergence circuit specifically. A normal TV shop will not allow a junior technician with little convergence repair experience to work on this problem. The inexperienced technician will damage the TV and cost money for a better technician to correct.

This repair is touted as simple and easy by the sellers of ICs, not by technicians that actually do the repair on a regular basis.

easyab
 
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