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JVC AV56WP74 Chips replaced, still having CV Problems

9K views 30 replies 5 participants last post by  lcaillo 
#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?
 
#2 ·
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?
 
#4 ·
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.
 
#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?
 
#6 ·
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.
 
#11 ·
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.
 
#14 ·
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
 
#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
 
#16 ·
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.
 
#20 · (Edited)
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
 
#21 ·
I am sorry but there is much misinformation in your post. First, there may be differences in the ICs, which is why I generally do not recommend subbing them unless one has direct experience with a particular model or the manufacturer recommends it. In the case of the JVC here, I have used it many time with never a problem. If the chip runs identically, with only minor convergence touch up needed (which is often the case with using the original part) and the IC does not run hot, and the d.c. offset is minimal, then there is unlikely to be any issue with subbing it. The reason that the STK394-160 is considered to be a superior part to the STK392-110 is that it has about 10% better thermal efficiency. They run cooler in the same circuit in the sets that I have measured, doing the same job, correcting the convergence identically. I have heard of some sets with problems, which is why I suggest caution with any subsitution.

Second, these repairs are often trivial, and techs often boast of how they do nothing but change the ICs, maybe a resistor and fuse, and hit some auto convergence mode and never bother to deo much more. I have gone behind enough of them to know that the level of service that most shops provide is an embarrassment to the service industry, at least those of us who take pride in our work.

I have been servicing projection television for 32 years and am online with hundreds of other techs. I provide service support for numerous service shops and have trained other technicians in the repair of convergence circuits. I find repeatedly that most shops do NOT have any special expertise in these repairs, and in fact do not pay attention to even the most basic considerations in servicing these problems. They do not typically distinguish which level of expertise they use to repair these problems. In fact, the majority do little more than swap ICs and don't bother to make basic checks. Many use inferior parts that do not last and do very little to adjust the sets at all.

Much of the reason that people DIY these repairs is the very poor level of service that is provided by "professionals" and the outrageous rates that are charged for repairs that leave the user to finish the alignment or perhaps correct the repair. There are many quality servicers out there who do good work a a fair price, but there are also many servicers who are condescending, disrespectful, do not do their homework, and are poorly informed.

Please refrain from attempting to scare people off of DIY repairs and show our users the respect they deserve when they do the research and do work for themselves. Comments like "Find competent help or you will never use the TV again" are not helpful. Read the threads here and you will find that many users have great success fixing sets that would otherwise end up in landfills.

You might find the first ten posts of the convergence repair sticky very informative:
http://www.hometheatershack.com/for.../5600-crt-based-rptv-convergence-repairs.html
 
#22 ·
Hi Leonard (and all!),

My brother inlaw just picked one of these up for free off of CraigsList so I'll be hopping down to try and help him recover it in a couple weeks (he lives a couple hours away and we were headed down for a visit anyway).

I really like step by step directions rather than "check the resistors", etc.. In this case I'd really like that kind of information because I don't get down there that often so I'd like to order the parts early and bring everything I need with me so we can get this project done in one trip. I know it's hard to provide specific information though, which is why kits from vendors such tvrepairkits.com, servicemanuals.vstore.ca, etc. are probably not a bad buy as they provide this kinda specific info. Those companies tend to provide the specific chips that were in the units originally though and a lot of times a viable upgrade that many of us would like to take advantage of while we're going through all the effort is available so we're stuck either buying those kits and sticking with the original parts or going with the upgraded parts and looking for the specific information we need on forums such as this.

I've done some research and found the service manual and stuff and I thought I'd share what I'd gleaned from my travels around the net and post it here so others working on this model may benefit too. I also have a couple questions you may be able to help me with too.

*) The board with the convergence chips is mounted behind the speaker grill and cover.

*) The stock chips are STK392-110 (ICs 804 & 805). I've seen several recommendations for upgrades, such as:
STK392-150 - Recommended by Leonard as a good alternative for about any brand set
STK392-180 - Recommended in threads on other forums (a couple I found)
STK394-160 - Leonard commented in this thread he's used them successfully in JVCs (this model?)

What would you recommend to order for a "it should work the first time" repair?

At www.servicemanuals.vstore.ca I found they had a JVC Convergence Resistor Kit that had the following description:

"This kit contains the Metal oxide resistors for the AV48WP30 through 65WP30 model rear projection TVs. Also applies to the AV48WP74 - AV65WP74 series."

Below are the kit's contents. The kit description didn't list the JVC board part description so I took those out of the service manual for this unit. I also included what type of resistor the service manual listed it as and any other comments I thought were relavent.

(3) 220 ohm 2 watt OMF (Metal Oxide Film)
R843, R851, R859

(3) 150 ohm 2 watt OMF (Metal Oxide Film)
R847, R855, R863

(2) 1.5 ohm 1 watt MF (Metal Film)
R846, R854
Note: R846 = Red veritcal adjust

(2) 2.2 ohm 1 watt MF (Metal Film)
R842, R850
R842 = Red horizontal adjust

(1) 1.8 ohm 1 watt MF (Metal Film)
R862

(1) 3.3ohm 1 watt MF (Metal Film)
R858

Some of the above resistors are not available from Acme where I planned on ordering the STKs from (some they don't have, such as the 150 and 220 ohm 2 watt ones, others they have in higher wattages, such as the 1.5 ohm 1 watts - they just have 2 watt ones). Can you recommend a company for good quality resistors of these odd ohms/wattages?

Thanks! I'll try to remember to take a camera down so maybe I can add some pics to help others working on this model.

Thanks again, take care,

Steve
 
#23 ·
I am not familiar with that vendor so I do not know anything about what they are selling. I recommend using B&D or Acme for the ICs. Resistors are not really critical as long as you get metal, not carbon, and get the right values. Get a service manual and verify the values of the resistors for your set. Do not take chances on what others say.

Any of those chips are likely fine. I do not use the 392-180 in any sets that did not have them originally. the 392-150 is the safest choice. I have heard reports of problems using the 394-160 but have not experienced them in these sets. I suspect most of the problems with any of the chips are cheap copies and installation mistakes.
 
#24 ·
As usual, thanks Leonard!

I found that MCM electronics has all the resistors in the proper values, wattages, and compositions except for the 1.8 ohm 1 watt but fortunately Acme has those! 8->

(3) 220 ohm 2watt metal film resistors
R843, R851, R859
OMF (Metal Oxide Film)
MCM part # 440-220 .39/ea $1.17 total

(3) 150 ohm 2watt metal film resistors
R847, R855, R863
OMF (Metal Oxide Film)
MCM part # 440-150 .39/ea $1.17 total

(2) 1.5 ohm 1watt metal resistors
R846, R854
MF (Metal Film)
R846 = Red veritcal adjust
MCM part # 67-1.5 $1.09/10 $1.09 total

(2) 2.2 ohm 1watt metal film resistors
R842, R850
MF (Metal Film)
R842 = Red horizontal adjust
MCM part # 67-2.2 $1.09/10 $1.09 total

(1) 1.8 ohm 1watt metal film resistor
R862
MF (Metal Film)
Acme (no part number with online ordering) $1.59/10 $1.59 total

(1) 3.3ohm 1watt metal film resistor
R858
MF (Metal Film)
MCM part # 67-3.3 $1.09/10 $1.09 total

Hope the above helps others!

Take care,

Steve
 
#25 ·
Wow! Did some poking around on forum for more info on this unit and I ran across another thread and it detailed something I missed (but to my defense, I haven't studied the manual much yet) . . . there's a booby trap in these units that will disable the digital input if you don't take it apart correctly!

Leonard detailed it in this thread and even provided the service bulletins to show how to disable it and how to fix it if you inadvertantly trip it (thanks Leonard!).

It's already on the forum, but I feel it needs to be in this thread too just in case someone else is working on one of these and doesn't take the time to search the forum for other related threads.

http://www.hometheatershack.com/forums/jvc/14924-av56wp74-convergence-issue.html

I'm still just shaking my head . . . what is JVC thinking here?

/Steve
 
#26 ·
Hi Guys,

An update . . . I just returned from my brother-inlaws. As I posted earlier, he picked one of these up for free off of Craigs List.

We ran down this weekend so I could take a look at it. The set was in perfect condition - not a mark on it, screen was crystal clear with no scratches, etc.! The previous owners had taken excellent care of it! It was even pretty clean inside, hardly any dust at all!

We rolled up our sleeves and took it apart. My brother inlaw is a DIYer but has zero electrical experience -> He pitched right in though!

This TV is the easiest one to put convergence chips in I've ran across so far!!! The chips are on a thin rectangular board at the front of the tv set. You take the front panel off and there's a cut out in the cabinet that allows access to it. There are only six cables running to the board. The first one runs perpendicular and is on the middle, left side of the board. The other five run horizontal across the back of the board. The second cable is at the top left of the board (as looking from the front of the tv set) and unplugs. The third cable though we could not get to come loose - it's apparently not a socket/plug assembly but rather some sort of permanently attached header assembly. That cable breaks into three separate plugs on the other end. Two went back to the a/v input panel and plugged into a silver box on it (sorry, I didn't unhook it, my brother inlaw did and I forgot to look at what it was later). The third plug went to the circuit on the left CRT tube and was easy to unhook from the front as the CRTs are right there. The fourth, fifth, and sixth cables are the red/green/blue outputs that go to the CRTs and they unplugged easily. Once all the cables were unhooked the circuit board can be removed. It was easy too - it's got three plastic tabs at the front edge of the board, I just lifted up on the heat sinks for the STK chips and pried the first tab back, kept upward pressure and pried the other two back and the board came right up, then just pull forward a tad and it'll come right out.

The board it's self was easy to solder on - like the other convergence boards I've worked on, it's not overly dense in components so it's not bad to solder on. The STK chips are screwed to the heat sinks which I think I like better than clips as I know they are being held down firmly to the heat sinks. I had to gently pry the STKs loose from the heat sinks. When I did I was utterly surprised to find that one had heat sink grease on only about 2/3 of the chip! The other was worse! It was just a round blob in the middle of the chip and I"ll bet it only covered 1/3 of the chip surface! I'm amazed this unit ran 7 years that way!

The chips were easy to remove using the Radio Shack $12 desoldering iron/bulb unit. I also replaced all of the resistors listed in my earlier post. Most of the resistors were off white with the values stamped on them rather than the more traditional appearing ones with color bands to denote their values. All visually looked OK except for R843. Both ends of it were dark brown. I don't normally test the convergence resistors as to do it right you need to pull one leg up and if I'm going to half unsolder it it's not that much more to just fully unsolder it and put in new ones. I did test the R843 that looked bad though and it was infinite resistance so it was definitely bad.

I replaced the STK392-110 chips with STK392-150s from Acme in Orlando. I considered the 394-160s as Leonard has done several of these sets successfully with them but he did mention others had reported having problems with this sub and it's a couple hour trip and both families have busy schedules so I didn't want to risk them not working and having to make another trip down as it would probably be hard to get that lined up in the near future and I hate setting projects aside and having to pick them back up weeks later. The 150s were just the safer bet for "works the first time".

I installed the 150s with Arctic Silver heat sink paste. Probably over kill, but I work on PCs all the time so I always have some on hand. I replaced all the resistors too without incident. All the resistors are lined up just in front of the STKs on the board, no hunting - they are all easy to find.

We reinstalled the board - that was simple, there are two horizaontal holders the back edge of the pcb goes into, just start the edge of the pcb into those holders and then press down and the board will snap down past the from connectors and slide right into place. We then replaced the front and rear cover panels as there is a sort of trap in these units that will disable the digital input if you fire it up with the back panel off (see earlier post above about this). Finally we fired it up - it fired up with no problems but the convergence was off. We went into the menus and pulled up the auto convergence. It took a minute or so and when it was done a gorgeous picture popped on for us! :D We let it run for an hour or so and did the auto convergence again, then I also did a manual convergence. The auto got it close so I just had to touch up the corners a tad with the manual convergence.

The picture it made was GORGEOUS! The thing is HEAVY too! My son's 51" Magnavox is more akward than heavy, but this JVC is definitely a chunk! I'm thinking that speaks to build quality - the Magnavox has some lower end particle board for the cabinet, a plastic mirror, etc.. This unit seems to have a little better particle board in the cabinet, and I noticed the mirror was glass.

All in all my brother inlaw was ecstatic! And I hope I'm not jinxing anything, but I found this tv almost FUN to work on! It's really easy compared to the Toshiba and Magnavox units I started this hobby with! I would like a big screen for our family room and I think I'm putting JVC on the short list of brands to look for!

I hope the above helps someone else - if you have one of these units and are wondering if you can really do this yourself or not the answer is yes, you can! I imagine that's the answer for most of these rear projections, but some are harder than others and I'd say from my very limited experience that there probably aren't many easier than this model (for convergence chips anyway, I have no idea on anything else)!

Take Care,

Steve
 
#27 ·
Hi Leonard (and all),

I just picked one of these up for myself . . . I figured it was time I got a rptv of my own to work on and the family room needed a bigger tv anyway.

I would like to try the 394-160 chips in mine since if there are problems it'll be where I can easily work on it instead of hours away like my brother-inlaws was.

I saw in your thread on convergence chips that you said that Hitachi orginally used the 392-150s in these kits and later went to the 160s but some distributors still had the kits with 150s. I would really like to make sure I get the 160s. Encompass looked like they had the best price on the Hitachi kits, about $45 before shipping. Have you ordered from them lately, or where do you get your Hitachi kits from?

Thanks!

Steve
 
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