Its possible that the filter cap is bad but unless you've got a 1/4" 20 bolt in place of the fuse I would think that the fuse would pop. Typically a shorted VREG would blow the fuse too. I'd see if you can isolate the power supply sections output and drive a 60watt 120VAC bulbs with it for a while. If it lights up and the supply doesnt get warmer then normal then you know you problem lies in the horizontal deflection circuit. I'll look at a schematic and see if theres an easy way to isolate the supply.
K7000 medium res (paperboy) dead
- Thread starter shardian
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shardian
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I'm not familiar with this, so be patient with me - the bulb would be driven by the rectified DC side of the power circuit?
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shardian
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Normally I would think the same thing, but that resistor is pretty damn big and can absorb a fair amount of juice. That would seem to explain a partial failure of a fuse, right?
Yeah, the bulb would be driven by the output from the voltage regulator. On U5000's theres a jumper you lift to isolate the supply from the deflection circuits. Looks like you would have to cut a trace to do the same on the K7000. Or pull the flyback and a few other parts. I wouldnt recommend doing all that. Check the VR to see if it gets hot. Oh, check the HOT to see if its getting too hot as well. If either of them are that flyback may be your problem (you said you checked the HOT and it was good). DONT check them for heat while the monitor is powered up!
Matt
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shardian
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C55 ohms out at around 180 ohms and stays there. Is that shorted?
R302 (the big resistor on the side that I mistook for R102) tests okay resistance wise. It still starts baking on power up, and yes, the fuse is still good obviously.
R104, 105 get hot - 105 was really hot. It is a large brown disc cap near C55.
HOT still okay. HOT and VREG were still cool to touch, so I don't think they are even seeing any power. I didn't notice anything feeling hot while poking around after shutdown.
R302 (the big resistor on the side that I mistook for R102) tests okay resistance wise. It still starts baking on power up, and yes, the fuse is still good obviously.
R104, 105 get hot - 105 was really hot. It is a large brown disc cap near C55.
HOT still okay. HOT and VREG were still cool to touch, so I don't think they are even seeing any power. I didn't notice anything feeling hot while poking around after shutdown.
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shardian
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R104, R105 are apparently part of the degauss circuit. Each lead of the deguass connector has a resistor, then a diode. For the record, I had the degauss cable disconnected for this test. Why would these resistors be hot then? Maybe that is a clue to someone better at troubleshooting than I?
On that note, it seems there are a few monitor guru's that aren't here anymore. That sucks...
On that note, it seems there are a few monitor guru's that aren't here anymore. That sucks...
Are you testing C55 in or out of circuit?
R105 is a thermistor so it getting hot is probably normal. R104 and R105 might be getting hot because you have the coil unplugged. Have you ever powered up a K6100 chassis with the degaussing coil unplugged? Ever see that resistor smoke for a split second? Its the same sort of deal.
Back to C55 ohming out at 180 ohms... If your getting that reading out of circuit its bad for sure. In circuit and I still think that your VR is to blame. If you took it out and measured it I'd be willing to bet that pins 3 and 4 are shorted together.
Does your monitor have the 4 pin STR3123 or the 5 pin STR30123?
Matt
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shardian
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STR3123 - it is the same as I took out.
C55 is in circuit still. I'll pull it out today and ohm it.
I ohmed the VREG in circuit, but wasn't sure what legs to ohm. 1&2 have continuity , 3&4 are open.
C55 is in circuit still. I'll pull it out today and ohm it.
I ohmed the VREG in circuit, but wasn't sure what legs to ohm. 1&2 have continuity , 3&4 are open.
What kind of continuity are you seeing between pins 1 and 2? Theres 10k in resistors nearby.
Matt
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shardian
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Pulled C55 - it tests fine out of circuit.
Tested VREG in circuit, 3&4 are shorted. I tested the old VREG I pulled - tests fine. So, I pulled the new Vreg and tested out of circuit - tests fine!
I need someone to verify something for me - the red and blue leads coming off of the large R302 resistor - I need to know where they go on the board. I disconnected them originally when I installed the VREG, because it is easier that way. I am fairly certain I took a picture so I could remember which wire went where. Maybe I got them backwards still.
Currently, I have red going near the first pin on VREG, and blue going down there by the cut off VREG 5th leg. Is that right? Should it even matter? It's just a resistor...
Tested VREG in circuit, 3&4 are shorted. I tested the old VREG I pulled - tests fine. So, I pulled the new Vreg and tested out of circuit - tests fine!
I need someone to verify something for me - the red and blue leads coming off of the large R302 resistor - I need to know where they go on the board. I disconnected them originally when I installed the VREG, because it is easier that way. I am fairly certain I took a picture so I could remember which wire went where. Maybe I got them backwards still.
Currently, I have red going near the first pin on VREG, and blue going down there by the cut off VREG 5th leg. Is that right? Should it even matter? It's just a resistor...
5th leg? STR3123's only have 4 legs. Isnt that what you said you had in the board? That resistor should be across pins 1 and 4 and doesnt matter which wire goes where.
Looking at the schematics pin 3 on the reg is GND and pin 4 is the b+ output. In order for you to have a short between pins 3 and 4 either c57 is bad (unlikely), the flyback is bad ( likely at this point), C36 is bad, the HOT is bad (which you mentioned is fine) or C204 on the neck board is shorted. I suppose that theres also a chance that T2 is internally shorted but I doubt it.
Keep the info coming, we will get this worked out!
Matt
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shardian
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I meant where the 5th leg is supposed to be. A 3123 is the same case as a 5 leg, but the 5th leg is snapped off. Sorry for the confusion.
If the fly was bad (new fly bad?) wouldn't the fuse blow or at least give me some firework life?
What is T2?
C204 is the cap on the neck that gets replaced, right? I replaced that one. I remember that it's polarity isn't normally marked, but I marked it on the board myself before pulling it. It should be in correctly, but I'll double check.
If the fly was bad (new fly bad?) wouldn't the fuse blow or at least give me some firework life?
What is T2?
C204 is the cap on the neck that gets replaced, right? I replaced that one. I remember that it's polarity isn't normally marked, but I marked it on the board myself before pulling it. It should be in correctly, but I'll double check.
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Bump because I still don't know what T2 is.
Surely something is shorted in the power circuit since parts are testing shorted in circuit, but fine out of circuit. Tonight I will pull all of the power circuit diodes and test them. I haven't done any diode checking yet.
I will also take a handful of pictures. If you guys would kindly take a look at them and see if anything jumps out at you, I would appreciate it.
Surely something is shorted in the power circuit since parts are testing shorted in circuit, but fine out of circuit. Tonight I will pull all of the power circuit diodes and test them. I haven't done any diode checking yet.
I will also take a handful of pictures. If you guys would kindly take a look at them and see if anything jumps out at you, I would appreciate it.
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After screwing with the 720 for a few hours tonight to only be rewarded with...nothing, I looked at this chassis again. My soldapult broke, so pulling diodes is out of the question for now. Then I started to think - why bother? I'll just spend a few hours screwing with it only to find out it isn't the problem.
I've officially given up on this chassis. If anyone wants to give it a go, let me know. I'll pay $50 labor + parts to anyone who wants to fix it (in a timely manner). Surely after all the troubleshooting I've already done, a veteran guru wouldn't take but an hour to fix this or deem it unworthy.
I've also posted a want to buy thread looking for a working chassis. If any of you guys have a spare, hook a bro up.
I've officially given up on this chassis. If anyone wants to give it a go, let me know. I'll pay $50 labor + parts to anyone who wants to fix it (in a timely manner). Surely after all the troubleshooting I've already done, a veteran guru wouldn't take but an hour to fix this or deem it unworthy.
I've also posted a want to buy thread looking for a working chassis. If any of you guys have a spare, hook a bro up.
modessitt
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What's your problem now? Won't power up?
Well, I don't have a medium-res game or yoke anymore, but I could at least get it to power up. I just wouldn't be able to get a pic to see if it needs anything else. If you have further problems after that, you can continue with your repair.
Otherwise check with Dokert. He has a Paperboy...
Well, I don't have a medium-res game or yoke anymore, but I could at least get it to power up. I just wouldn't be able to get a pic to see if it needs anything else. If you have further problems after that, you can continue with your repair.
Otherwise check with Dokert. He has a Paperboy...
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shardian
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My problem almost assuredly lies in the power section of the board. I'd prefer to get it repaired by someone who could test it though.
Beggars can't be choosers. Mod got my WG6100 going. I have faith.
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shardian
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I was under the impression this chassis needed a load (tube) in order to power up properly. If that is not the case, then Mod can have at it.
