# Looking for a tech,please help zenith r56w36 chassis sp02pc



## evilpea

I have a zenith model r56w36 chassis sp02pc, I dont have a manual nor can I find one, sorry. I picked this tv up for a cool 20$ spot with a convergence issue..... I thought it would be a simple ic exchange but it turned into everything but. Found some swollen caps on the convergence board replaced them, esr meter said only one was bad but 4 others were swollen and leaking electrolyte so I replaced them as well. also found some resistors burned and replaced them with close to the same thing about .5 ohms more than what was there pluged in and turned on and they light up like a christmas tree jerked plug out removed connections to board and tested the 26+ and 26- volts in, which were where the caps had swollen, got about 50-VDC on both..... so I traced the power back to the main PWR board and happend to notice by accident more swollen caps on the 26+ and 26- output trac on the main PWR board, they were swollen on the bottom. The caps are c849 c850 c852. This is where I need a little help.... I took PWR board out so I can work just on it, when I plugged it in I wouldnt get any voltage so I looked at the board and found relay RL802 and think it is responsible for power on sequence so I shorted the gate terminals on it but am only reading 2 or 3 VAC on the secondary side of the transformer for 26+ and 26- and only 15VAC on the primary side. Am I shorting the wrong thing or why would I not be getting the voltage to the primary side? I tried tracing it out but its a little beyond me. It seems like everything on the primary side gets to D801-,4 terminal marked RBV-606, and stops. If anyone could help me I would be eternally greatfull.


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## evilpea

Update I found the transistor responsible for closing the gate on the relay, I think it's q804. The strangest thing happened after I shorted it and heard the relay click like its supposed to, I tested the secondary voltage for the 26+ and 26- I got the same results as before when I just shorted the relay itself but this time I touched the heat sink for ic 801 and got bitten, what could I have done to make the grounds live with 120volts?


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## lcaillo

Try looking at http://elektrotanya.com/ for your manual. It is very difficult to do troubleshooting without at least a schematic.

You should be very careful about working on a live set, particularly if you do not understand the design of power supplies and grounding. Not all of what you might expect are grounds are at the same potential.


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## evilpea

Icaillo, thank you for the reply I tried there but they didn't have it. How ever I thought I had exausted all my resources but went back to some of my old ones and was able to find the manual, tried attaching it here but wasnt able to due to a missing token? Here is a link to it(tried leaving a full link but website wont let me) techlore.com/download/38848/Zenith-Model-R56W36-Chassis-SP02PC/ When I placed the swollen caps back in the board I got 50 or 60 volts again on the 26+ output on the smps board.


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## evilpea

In the schematic on page 54 I see the POWER terminal 12 on connection P810A goes to two relays,RL802 and RL801, but I only have one being RL802 on my board. I see that terminal 12 closes the gate on RL802 in order to start primary on T802. For the stby I get 28VAC. Your guidence is very welcome on how to "start" the board. Thanks again


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## lcaillo

You need to be sure that you have the right version of the set.


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## evilpea

other than not having the relay 801 everything else is there.


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## evilpea

Also in the manual it says there are optional components for optional stuff, I guess my set came without those options.


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## evilpea

So was I right about the q804 being responsible for starting the primary on t802?


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## evilpea

It's been almost a week and nothing... I was told by some people that I could get some information from some intelligent caring technicians who didn't mind sharing their knowledge with others....Guess they were wrong.


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## lcaillo

No, they were not wrong at all. I have, as have others, shared much knowledge and do care. The many hours that go into the forum on the part of users, admins, and moderators here is clear proof of that. What we do not do is step by step analysis and troubleshooting for every problem. If someone knew the power supply in your set well enough, or happened to have a schematic handy, I am certain you would have received an answer to your question. You have a dated product that not very many owners spend the money to have repaired any more, and most of the techs who would have had familiarity with it in the detail needed to answer your question have likely not seen one in years. 

If you want to post an image of the power supply schematic someone might be able to answer your question. I know I have not worked on one of these sets in at least 4 years and do not have a manual in my files. Without context of the circuit design and a schematic, Q804 could be anything.

There are many other forums if you don't find what you need here. We clearly state in the Service and Support stickies the nature of the help we provide. It does not include taking the time to download the manual and walking you through the analysis and troubleshooting.


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## evilpea

I wasn't looking for some one to do it for me, just a little help in what i'm trying to accomplish, from someone more experianced and knowledgeable. I know exactly what you mean about the many hours of moderating. I thought posting a link to the manual would be sufficient for someone to take a quick look, as well they would then have that manual in there files if they ever needed it. I Have attached the schematic. On my board RL802 is relay RL801 in the schematic, shorting pins 1&2 on relay RL801 would be equivalent to turning it on right? I see that the stby power goes to both collectors? of q803 and q804 from pin 3 of ic807. Power comes in to the base? of q803 which sends the power from the output of pin3 on ic807 from the emitter to the base of q804? which then sends the power from pin3 of ic807 from its emitter to ground from pin 2 of ic807 to complete the circuit? am I even close to being correct on that? or should I just short pins 1&2 on RL801?


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## lcaillo

Yes, when Q804 conducts, current flows which energizes the relay. In order to get current flowing through the coil in the primary of the relay, you have to turn on Q804. This accomplishes the same thing as shorting the pins on the contact side of the relay, without the danger of working on the hot side of the supply.

I would not assume that the power supply will run without a load, nor that you won't damage something by testing it this way. I would not be taking the path you have to troubleshoot, so it is hard to answer your questions out of the context of having the set to make the checks that I would normally make. The first thing that I would have done is to run the set without the STKs and check the power supplies.

You said you measured 50 volts on each of the supply rails to the chips, but what were the other supplies? What were you using as a reference? To get twice the dc voltage on the convergence supplies would be unlikely.

From the nature of your questions I have to ask that you be very careful about working on your set and this power supply. IC 801 is on the primary side of the supply and the grounds will be hot. If you are assuming them to be safe, or using them as reference for measurements on the secondary side you are living dangerously. As a professional technician I have to warn you against troubleshooting these sorts of problems without the proper expertise and equipment. It sounds like the power supply is working because you had enough current to light up your resistors. When these supplies run, they usually run properly or shut down right away if there is a regulation problem.


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## evilpea

I was not aware that the T801 needed a load to start, I thought as long as the primary side has voltage going to it the secondary side would be energized no matter what, That's probably why I wasn't getting any voltage on the secondary side when I shorted pins 1&2 on RL801. Good news per your advice I reinstalled the SMPS board and removed the IC's and replaced the resistors and turned the tv on it still works but with the convergence issue so atleast I got lucky and didn't mess the SMPS board up. On the CVG OUT board that I have attached the schematic to I was using the cold/chassis ground that is in between the 26+ and 26- on the connection P003B to test the 26+ 26- and 5+ and 5- on the 5+ and 5- they stay within tolerance never above 5 volts on the 26 + and - I get around 46VDC at the connection P003B. By the way my reference of what the volts should be is the voltages that are printed on the board by the connection. Since all caps on my 26 + and - were swollen even on the SMPS board I figured that is where my problem is originating from, which is why I took it out and was trying to start it so I could focus my attention on it. Looking at the schematic of the SMPS could you suggest a way to load it so it starts? or where to go from here? Icaillo thank you for your continued support and guidance, If I could have gotten answers like these along time ago I would be a lot further ahead than I am now in life and with my degree.


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## evilpea

Sorry the other schematic of the board exceeded the limit so here are a couple of blown up jpegs of where and what I was testing for the 26 + and 26-.


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## lcaillo

When I say reference for voltage measurements, I mean what ground you are using. If you use a hot ground your readings will not make sense. You have to be using the proper ground for the circuit, which is probably the cold chassis ground, but some convergence circuits float ground as well. I don't think this set does, but using the ground pin(s) on the ICs would be the sure way to know you are measuring correctly.

You need to be very careful. I cannot possibly tell you in a thread like this all of the things that a tech would routinely do to be safe and effective in troubleshooting a problem like this. There are serious hazards to working on SMPSs and televisions. the fact that you got "bit" by a hot ground on the primary side of the power supply and don't seem to understand basic troubleshooting is a concern. Be cautious and assume nothing. There are plenty of good tutorials out there on troubleshooting and general electronics that cover safety. One of the best is Sam Goldwasser's web site.
http://www.repairfaq.org/REPAIR/


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## evilpea

Im fully aware of the dangers of electricity. I should probably be using an isolation transformer and or a cgfi plug with wrist strap to ground. I never work on it alone only when my girl friend is present, she likes the idea that I told she can kick me if I start shaking. I did not say I got bit by a HOT ground. Maybe you miss read it. The ground I brushed with my hand was a heat sink for ic801 to see if it was getting warm. That heat sink is on the cold ground, that heat sink is not supposed to be HOT as stated in previous post. I know the difference in grounds thats why I used the cold ground to test the 26 feeds.


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## lcaillo

You said "I touched the heat sink for ic 801 and got bitten, what could I have done to make the grounds live with 120volts?"

IC801 is on the primary side of the power supply. The primary and secondary do not share grounds in this type of system. The grounds on the primary side are considered hot grounds. Most schematics use different designations for primary and secondary grounds, this one does not. Note however the triangles with the exclamation points on the primary side of the optocouplers and transformers. These indicate that this side is not isolated.

An isolation transformer is a very important safety item. One should work with the same cautions with or without one, however.

What do the rest of the voltages out of the power supply rise to? Which caps, precisely, were swollen? Details are important to troubleshooting.

Your power supply may not need a load to start, but may need one to run efficiently or to regulate. Most supplies can be started and run for a short period, but you can also do damage to some unloaded. If you had swollen caps and high voltage, this suggests a regulation problem. I would check the components on the primary side and in the feedback from the secondary and look for problems there if the secondary voltages are rising significantly over where they should be. Most supplies would just shut down, but perhaps this one will not.


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## evilpea

I just got finished with homework I went back and looked at the schematic. It was there as plain as day.... I guess being dumb is part of learning. Just looking at the board alone I thought it was connected to the chassis ground. I see what you mean about ic803 the triangle on the HOT side of the optoisolator thank you for clearing that up for me, guess I should have caught that in the manual before sticking my fingers where they do not belong. I will check on the rest of the voltages for the power supply and report back tomorow. Is your signature from the John Locke off of Lost one in the same? I loved that show and wish they would bring it back.


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## lcaillo

John Locke was a 17th century English philosopher, generally considered one of the most significant among empiricists of the time. 

The Lost series was apparently over my head. I watched it for a while and never quite got it.


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## evilpea

It is funny that you mention John Locke the philosopher we just covered, lightly, his theory of "the blank slate" in class. Sorry it took me so long on the reply I was swamped with school. Here are my finding on the other voltages, all seen normal or close to normal execpt the 26+ and 26-. The swollen caps are C849,850,852 on the smps board. On connection P812A (Terminal 8) 35V bounces around at 35VDC to 36VDC. (Terminal 2)110 bounces around at 110VDC to 111VDC. (Terminal 1) 115V bounces around at 116VDC to 117VDC. On connection P810A (Terminal 10) 12V bounces around at 12VDC to 13VDC. (Terminal 8) 8V bounces around at 7VDC to 8VDC. (Terminal 6) 5V bounces around at 4.5VDC to 5.3VDC. (Terminal 2&1) S-40v bounces around at 39VDC to 40VDC.


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## lcaillo

What are the 26 and -26v lines measuring?


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## evilpea

47 to 48 on 26+ and -47 to -48 on 26-. I see a few resistors and caps and a transistor that I am going to test on the primary side I will get back to you with the results. Looking at the board I am having trouble identifying the pins on the primary side that power the 26 on the secondary side. On my board it looks like pins 7 and 12, which are straight across from the 26 feeds, drive the 26 feeds. In the shematic it it looks like pins 2 and 4 drive the 26 feeds. Any input on this would help. Thank you again for your continued support.


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## lcaillo

Where exactly are you taking these measurements and what ground point are you using?


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## evilpea

I am taking theses measurements straight from the terminals on connections P810A and P812A since all of these are on the secondary side of the transformer I was using the cold/chassis ground but will go back and make sure it was the cold ground in the schematic. On the 26 feeds I was using the ground terminals between both 26 feed terminals.


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## evilpea

Terminal 8&9 on connection P811A are the designated grounds for the 26 feeds according to schematic. That is what i was using to test them. I traced all components from terminal 2, 3, 4, 7, 12. On the primary of transformer 801 all the way back to their origins. All seemed fine. Their were a couple of disc caps that I could not test, my preliminary test on Q801 turned out good but I will pull it from the board and put it in my tester to make sure. The only other thing I can not test is the IC801. Could this IC cause my voltage to double on the secondary side? Or could this possibly be a bad transformer?


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## lcaillo

High output on a switching supply is usually a failure in the feedback circuit or the regulator itself. Almost never a transformer. The fact that both sides, +/- are high makes me think something on the primary side with the regulator or related parts.


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## evilpea

Would the feed back circuit and regulator be on the SMPS board or the convergence output board? I am not seeing anything that would resemble either one on the SMPS board.


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## lcaillo

The feedback is from error amp IC806 to optocoupler IC804.


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## evilpea

IC806 & IC804 are part of the optional parts that does not exist on my board. Would IC803 and IC805 be the equivelant process to IC806 & IC804?


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## evilpea

It looks like the IC805 only regulates the 35V and the 110V. There is no regulating the 26 feeds unless it is done through the primary side of the optoisolator IC803?


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## evilpea

I have come to a revelation the primary pins that drive the 26 feeds also drive the 12 ,8, and 5.5 volts I think if it was a primary problem wouldn't it mess with these voltages as well? I think it is picking up the extra voltage on down the line somewhere on the secondary side of the 26 feeds. I tested the voltage from the secondary pins of the transformer for the 26 feeds, they were both constant AC current, one was 8VAC and the other feed was 15VAC. I see in the schematic that diodes D817 and D818 rectify the voltage to DC I will get a reading on the cathode of these diodes tomorrow and see what the rectified voltage is.


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## evilpea

Here are my strange findings. On the 26+ secondary terminal from the transformer it goes from a constant 8VAC/0VDC (before the diode/anode) D817 to 105VAC?/48VDC (after the diode/cathode). The 26- goes from 15VAC/0VDC (before the diode/anode) D818 to 48VDC/0VAC (after the diode/cathode). I Will look at the board tonite and see if I can figure out how the 26+ is being feed with mains power!?! Untill then any thoughts?


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## lcaillo

Do you understand the basic principles of operation for switching power supplies?


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## evilpea

I have a general idea. I have not been in such an in depth circuit before. My first semester of EE is next semester or the one after that, depends on when my equipment comes in. If I were more experianced I would not be here looking for someone with experiance to help me, it pains me to be ignorant. I can not see why people with more experiance here can not see it as simply as I do. It does not seem that complex. I am supposed to be getting 26+ output I am not, I am getting double. I realize that after the coil/choke much of that high frequency AC current will disappear, probably to the voltage that is doubled 48V, here is my question why is there AC voltage after the diode period. The circuit is a bit to complex for me at this point, that is why I am here, to seek the guidance of someone more experianced that is willing to help me. The answer is not as simple as the problem. I have searched extensively for information that would relate to my problem and how to diagnose it, no luck. You are my last hope for intelligence.


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## lcaillo

There is nothing wrong with not knowing and seeking help. What we can do is limited, but sometimes we can be informative.

So the (very) basic idea is this...you have a.c. mains rectified by the main bridge diodes. That d.c. is applied to the switching transformer and switched on and off at a high rate (anywhere from a few tens to a few hundreds of kHz). That creates a field that rises and collapses in the secondary, thus the current that will be used by the set. The controlling IC on the primary side controls the rate of switching, either by varying the rate of a constant width pulse, or by varying the width of the pulses (PWM). In this case, the current is switched on/off by the FET in the IC. Note that the feedback from the optocoupler is applied to the input of the IC (also controlling the oscilator and providing the latch for overvoltage) as well as to the comparator that drives the oscillator. Control is effected by a combination of switching of the FET and saturation in the windings of the transformer ( control windings with the 2sc3852 transistor referenced with a zener diode). This is why it is unlikely to get an overvoltage problem on the secondary unless there is a problem in the feedback (like the error amp malfunctioning, but they usually will shut it down).

You are correct that on the secondary the diode rectifies, and the cap and coil filter what is left of the switching pulses.

Check the continuity of the grounds on the secondary side.


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## evilpea

HA you just made me feel dumb, thank you it has been a long time since someone was able to do that. I just came to the realization that FET-Stands for field effect transistor, having known this since I was 10 it did not really occur to me that the FET was used to run the primary side in order to energize the secondary side. I knew that DC voltage alone would not energize the secondary side because the only change in field was when it was turned on and off, and thought that is why they used ac to power the primary...but I always seen rectified dc going into them and never could figure out why. Now I know its because of the (Field Effect Transistor). duh it makes since to me, NOW. I was not aware that the FET accomplished this by turning on and off rapidly. The reason I do not hink it is a primary side problem is because the primary, I think, drives four different voltages (26+&-V, 12V, 8V, 5.5V) If I am thinking correctly they wound the secondary windings to accommodate these different voltages from the primary windings, so the primary puts out constant and the secondary takes what it can get,with a certain amount of windings, to create the out put voltage that it is supposed to. If it were a primary voltage problem would it not affect all of the voltage outputs on the secondary instead of just the 26+&-? On the secondary ground continuity here are the results of it, all results with 200 ohm setting, 35V/115V GND to 40V GND is nothing, 40V GND to 26+&-V GND is nothing, 26+&-V GND to 115V/35V GND is infinate continuity or 0.1. Out of all of those the only one that does not have infinate continuity with the chassis ground is the 40V GND it reads nothing with the board unplugged from the rest of the chassis and laying on my desk for the test.


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## lcaillo

I am having a very hard time following your terminology. I don't know what you mean by "infinate continuity" though I believe it to be low ohms from your .1 value. I also don't know what "it reads nothing" means. Usually, an infinite resistance reading on a meter is an open circuit. Any other reading is whatever the resistance is, with 0 ohms being a perfect connection (which really does not exist). Most meters are not very accurate reading below an ohm or so, so you would consider fractions of an ohm to be a pretty good connection.

Yes, if only one voltage in a secondary is off, you would not suspect the primary. Look for a bad transformer, a bad connection, a cap installed backwards, IF everything is as described and you are using the proper references for your measurements.

It is very hard to give specific troubleshooting advice without having the set in front of me. When users are not familiar with the circuit design, do not use the proper or usual terminology, and time intervenes between posts, it is very difficult to keep track of what is going on. This is a perfect example of why we do not provide step by step troubleshooting in the forums. This is something that an experienced tech with the set present would have solved in a few checks. It is impossible to impart the observation skills and understanding of this kind of experience in a few posts dispersed over weeks.

I don't mean to be rude or to criticize your inexperience, but with a forum of over 70,000 members to administer, and a job and family, it simply is not practical to help everyone through every step of a problem. I hope that I have been informative and helpful, but I have to limit any more time on this. I must stick to our policy regarding specific troubleshooting advice and limit help to more general questions about the technology.


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## evilpea

I thought infinite was universally standard, meaning forever, accompanied by continuity means forever continuity. That is why I also put the actual reading from the meter, just in case their is some confusion in the meaning of infinite. For the "it read nothing" That means the meter did not change so it did not give a reading meaning it read nothing. I apologize for the delayed post's by the time I get done with all my school work and home and work responsibilities all I want to do is relax, the week end is the only time I have a day to work on this. Their are no caps backwards but I am still using the swollen caps that I mention earlier because I do not have quick access to replacements so I was going to buy all parts at the same time ounce I get everything working right, I see no since in buying expensive convergence ic's if I can not fix the power issue that likely blew the other ones. Could these capacitors on the 26 feed that are swollen cause this voltage problem even though my esr meter said they were within tolerance? My esr meter reads esr&dc resistance.


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## lcaillo

I would not expect swollen caps to cause these high readings. The swollen caps are likely because of excessive voltage across them. There is obviously something that is being missed here, but I do not know what it is. I simply don't have the time to dig in to the circuit nor to go back and parse the info in the thread to see what might be going on.


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## evilpea

Well thank you for your time anyway. I will not give up on it yet. I am still searching for an answer and will continue to untill I, get so fed up I just throw the board in the trash and kick the rest of the set across the yard or, find out what is causing the problem. There is not much between the diodes on the 26 feed and the output connection, this is where I am sure my problem is coming from. I looked at it a little bit today but did not get anywhere on it because of school, yet another seemingly endless week of it. I even went to the local electronic shop, if you can call it that, to look for replacement caps to ensure they are not the cause but they were closed for the holiday, but like you I think they are a result of the extraordinarily high voltage. I will still keep you/everyone else updated on the progress if I make any.


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## evilpea

Well I can say with certainty that it is not the capacitors on the SMPS board, I never really thought it was but what the hey might as well I have ran out of things to test on the SMPS board. On to the convergence output board maybe something is causing some kind of weird feed back issue, I am thinking maybe a shorted transistor somewhere. All the ones I tested on the SMPS board came out good but it could still be intermittent which I can not test for because I have nothing to read them like a curve tracer.


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## evilpea

Well I figured it out, all is well. There were no chips to pull the voltage down so it appeared as over voltage. Replaced everything and it works great. Now all I need is a way into the service menu so I can make some small adjustments to the convergence, any help with task would be awsome.


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