Re: Rca l26wd12
I reckon, unless somebody can tell me different, I'm at the end of the road with this tv. As far as I can tell, there's no way of replacing this bad inductor short of getting a new power board. The only markings on it seem to be in-house, for the same company that made the board. I found a few places carrying the board, but they were all out of stock, and it would run close to $100 if it was in stock. Found one board that sold on Ebay a few weeks ago, but even it went for close to that price. And that's more than I really want to spend on a pretty old (and heavy!)...
chiefjoe
Member
Last Activity: 01-18-2024, 09:18 AM
Joined: 11-16-2005
Location: Miss'ippi, USA
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Re: Rca l26wd12
So. I started out thinking I would make an audio recording of the buzzing, and upload it to youtube, and maybe get somebody to tell me what they thought the noise was. Here's that recording:
[url]http://youtu.be/vFbDYyxStsM[/url]
As I'm playing it back, I realize the buzzing got louder and quieter, as I moved the mic around. A light bulb went on over my head. I took another recording, this time with headphones on listening to the mic, as I passed it over parts of the board. The buzzing is loudest when I pass over the L2 inductor that...Leave a comment:
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Re: Rca l26wd12
I got a dim bulb tester hacked together, soldered everything back in (with new Q7 and Q2, and a new fuse), and hooked everything up. I gave it a quick test, going through a Kill-A-Watt so I can keep an eye on the current. The bulb seems to be doing its job. When the relay clicks on, the buzzing sound is still happening, but it's a good bit quieter. The bulb comes on at about half brightness, and stays there (using a 100w bulb). According to the KillAWatt, it's pulling .56 amps, and at the connection coming into the power board, I'm getting 67.4 volts AC.
...Leave a comment:
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Re: Rca l26wd12
I've been telling you wrong. I just realized while looking at the schematic that the mosfet that shorted out after replacing everything is Q7. Now I'm trying to wrack my brain to remember rather Q7 was the one that was originally shorted, or Q2.
Just to triple check, and to make sure I know what the deal is now: Q2 & Q7 were both replaced. I've removed Q7 AND Q2; Q7 is now shorted, Q2 tests good. From the point that I said I soldered in the new parts, whenever I said Q2, I should have said Q7.
Sorry for the mixup.Leave a comment:
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Re: Rca l26wd12
Thanks Bill. I pulled D4, and it seems good. Doing a diode check, I'm getting .408 V one direction, open the other. Q5 was brand new. Doing a check on Q5 in circuit (it's smd, and I don't want to desolder it unless I need to) but with Q2 removed, I'm getting open on all pins when I check ohms.
Just for the sake of ruling it out, and to have something to test, I also removed the big capacitor (labled C3), and it tested good on a capacitive meter.
Looking at the schematic, I'm wondering about a couple of components just before Q2; an inductor,L2,...Last edited by chiefjoe; 11-01-2011, 08:55 PM.Leave a comment:
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Re: Rca l26wd12
Bump?Leave a comment:
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Re: Rca l26wd12
Anyone have ideas for what could be causing this mosfet to short out?
I dug around and turned up a schematic for the power board, I'm just a bit clueless about how to use it to track down a problem. Q2 is at the top, just underneath the heading for column 4.
Thanks...Leave a comment:
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Re: Rca l26wd12
Well, shoot. I had decided to replace everything I removed, and got the order in today. Soldered everything in, along with a new fuse, hooked everything back up, and gave it power. Soon as the relay clicked, something started buzzing. It lasted maybe 3 or 4 seconds, then quit. All I could tell was it came from the power supply board. After that, it acts just like it's been acting (red light, not power out from the power supply). I pulled the board back off, and the fuse was blown again. After fuming for a bit, I decided to pull the new Q2 to test it, and it's gone...Leave a comment:
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Re: Rca l26wd12
First off, thanks for the info & guidance.
Second, I've gotten all 4 unsoldered, and it looks like only Q2 is bad. Unsoldered, I'm getting the same reading as in-circuit. For the other 3, I'm getting open on all pins.
Does this mean I've got the problem found, or is there anything else I should check before heading to digikey?
A couple other questions: would you trust the other transistors I pulled (the ones that checked good) , or go ahead and replace them while I have them out?
Also, I'm a little...Leave a comment:
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Re: Rca l26wd12
Looks like that's the problem (or at least A problem). Here's the readings I got:
Q6 : pins B - C read 5.5 Ohms.
Q7 : A - B = 77.5, B - C = .2, A - C = 77.4
Q2 : A - B = .8, B - C = .2, A - C = .7
Q5 : B - C = 39.3
Every other reading besides these read open.Leave a comment:
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Re: Rca l26wd12
What would be the right way to test for shorts? Thanks.Leave a comment:
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Re: Rca l26wd12
I finally managed to get the thing unsoldered.
Pins are + ~ ~ -
+ to ~ readings are: 4.68 Mohm one way, open the other
~ to ~ open both ways
~ to - 4.48 Mohm one way, open the other
The non-open readings were with the black probe on the left pin, red on the right.Leave a comment:
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Re: Rca l26wd12
The heatsink I'm getting a voltage on is the bottom one, and the fuse is at the top right....Leave a comment:
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Rca l26wd12
I picked up this LCD tv at a yard sale for $10. There was a sticker on it that said "Needs Work", and because I've been wanting a new project, I picked it up. I asked the guy selling it what was wrong with it, and all he said was that it needed a new power board. (I didn't think to ask him what kind of testing he'd done to get to that) I had just fixed up a Gateway monitor that needed new caps on its power supply, so I figured I'd either be able to swap out caps and it'd be a quick fix, or worst case scenario, I'd have a good educational experience. I should point out at the beginning... -
Re: soyo-k7v dragon plus
Wanted to add another dragon plus with bad caps. Was putting in a dvd drive the other day, and took a look around and dammit if i didn't have a whole line of bad caps. Thing is, I've never had any symptoms. No stability problems, no bsods, shutoffs, anything.
Any idea how long I have to replace? How dangerous would it be to wait til after christmas? Also, what would be a good (safe) replacement board, with room for 5 hard drives, and mounting holes for a cpu heatsink?Leave a comment:
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