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Looking for a tech,please help zenith r56w36 chassis sp02pc

7K views 42 replies 2 participants last post by  evilpea 
#1 ·
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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#2 ·
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?
 
#3 ·
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.
 
#4 ·
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.
 
#5 ·
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
 
#11 ·
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.
 
#12 ·
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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#13 ·
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.
 
#14 · (Edited)
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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#16 ·
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/
 
#17 ·
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.
 
#18 ·
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.
 
#19 ·
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.
 
#20 ·
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.
 
#21 ·
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.
 
#23 · (Edited)
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.
 
#25 ·
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.
 
#26 ·
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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