Thanks! Here are the measurements for H1... -31~0~5.3~0~4.9~5~5~5~5~4~0~0~4.8~4.6~4.8~4.8~0~0~0~0~5
Filament measures 7v AC when unit is powered on. 0v when powdered off.
I found Q257 on Main 1 PCB, but did you mean C270? I don't see C207. Unfortunately those are too deep to get to without a lot of disassembly. As far as C510, I measured 31v on one lead and 5.6v on the other lead....
JimBanville
Senior Member
Last Activity: 02-27-2024, 10:41 AM
Joined: 08-11-2020
Location: Columbus
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Help diagnosing dim VFD on Yamaha RX-V2400
I realize vacuum fluorescent displays degrade over time.
Potential "fixes" (temporary or permanent) seem to typically involve replacing capacitors powering the VFD, or the risky and temporary "fix" of high voltage across the filament to burn off contaminants.
Can someone look at these pics from the RX-V2400 service manual and give me a starting point in determining which step to take first? The display is almost too dim to even read, so if I damage it, so be it. It's borderline useless at this point. I already did a factory reset which didn't help. It looks like... -
Dim displays on Yamaha RX-V receivers
I have an RX-V2400 and another RX-V I can’t remember the model number at the moment. Both have very dim VFD displays. Both have been factory reset with no change. This seems like a common issue. Lots of talk about possible bad caps but I’ve never actually heard of anyone fixing the problem. Is it just bad caps or something else? Thanks! -
Re: MOSFET mystery
Will do! 👌🏼...Leave a comment:
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Re: MOSFET mystery
Gotcha. I appreciate it. Based on what research I had done on N channel mosfets in the last couple days, having never dealt with them before, including "recommended" videos on "how to test N channel mosfets", I was, and still am, puzzled how something can be tested in so many ways. Lol. Oh well, based on how I was finally able to trial-and-error figure out on my own how these particular mosfets are tested, I suppose they're fine and I'll move on to all the other components to figure out what's making this smps power cycle itself...Leave a comment:
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Re: MOSFET mystery
I have kept moving these probes around and discovered this...
I place - on drain and touch + to gate.
Then release both and place + on source and - on drain.
I then see a .3v reading.
While leaving + on source, touch gate with - then put - back on drain and see a .5v reading.
This is all contingent on me using the + probe on source.
If I do what W2AEW did in his video, - on source, I get nothing....Last edited by JimBanville; 09-15-2023, 01:58 PM.Leave a comment:
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Re: MOSFET mystery
Maybe my misunderstanding is that my mosfet requires more voltage to get the results he got. I watched several videos and read some articles and none mentioned that was a factor. I'd never tried testing a mosfet before. People were using DMM's similar to what I've got so I thought I'd be good. Thanks....Leave a comment:
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Re: MOSFET mystery
Ah. The video is pretty short. Can you tell me what I got wrong, please? I literally followed along and did exactly what he did. I'd like to know. Thanks! ✌🏼...Leave a comment:
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Re: MOSFET mystery
Uh. Ok. How about Reddit? The moderator of one of the electronics repairs subreddits referred my to the garbage YT video with bad info. Lol.
As you can imagine, diametrically opposed answers to these questions doesn't help someone learn.
I tried to recreate what W2AEW did in the video by placing - on S and + on D and, unlike W2AEW who got a .5v reading, I got OL. Only by reversing the probes did I get a .5v reading....Last edited by JimBanville; 09-15-2023, 01:02 PM.Leave a comment:
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Re: MOSFET mystery
Thank you!!!!
"+ to S, - to D => Test body diode, should be 0.5 volts drop for most mosfets"
^That^ is what I've wanted to know all along. Do you know why some people are saying to do - to S and + to D to get the .5 voltage reading, like this tutorial video I was referred to ... [url]https://youtu.be/gloikp9t2dA?si=IgNn2CgL-ofGiDxC[/url]
is it just wrong? Or did I misinterpret something? Thanks for being patient and helping my to learn 👍🏼Re: MOSFET mystery<br /> <br /> <b... Thank you!!!!...Leave a comment:
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Re: MOSFET mystery
Lol. Calm down. I said I'm a novice. I probably never uttered the word "mosfet" in my entire life prior to a couple days ago.
I'm aware there is a diode there. That's not a question. All the tutorials I've read on testing N channel mosfets have specially said to use the NEGATIVE probe on the source and the POSITIVE probe on the drain to test the mosfet. They never mention using the POSITIVE probe on the source and the NEGATIVE probe on the drain for any reason. That's the question I've been asking since I started this thread. ...Last edited by JimBanville; 09-15-2023, 12:17 PM.Leave a comment:
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Re: MOSFET mystery
Thanks. Will do.
Sorry if I'm sounding like a broken record, besides the possible inability to get the diode to charge (if that's what it's called - I'm a novice), what are your thoughts on the probes having to be reversed? Or am I doing it wrong?
What "should" you see if you place the positive probe on the source and negative probe on the drain on an N channel mosfet?
And why can't I seem to "short" the gate and drain?...Last edited by JimBanville; 09-15-2023, 11:39 AM.Leave a comment:
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Re: MOSFET mystery
Yes. And the mk168 tester identified the pins as that in the picture. Gate, drain, source, going left to right with printing on the mosfet facing you. I just installed a new battery into my fluke and I'm getting the same results.
Do you agree with everything I've read that I should be placing negative probe on the right/source pin and the positive probe on the center/drain pins to get a reading? That gives me OL. if I switch the polarity of the test probes, that's the only time I get a .49v reading from source to drain. Shorting the gate and...Leave a comment:
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Re: MOSFET mystery
I didn't mean failing as in broken/defective. I just meant failing to do the job in this case. But my question is, why am I only getting a reading from the diode with the probes in opposite orientation to "correct" on the source and drain? And why can't I short the gate and drain to see OL between source and drain, unless the fact that because I'm having to use the probes in an opposite orientation, I keep charging it? Sort of a catch 22 situation....Leave a comment:
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Re: MOSFET mystery
If my fluke 115 is failing, is that causing me to look at this backwards?
If you discharge the mosfet and test it "opposite" of correct (probes in opposite orientation), would you get the readings I'm getting?Leave a comment:
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Re: MOSFET mystery
I don't know how helpful this will be, but...
if I place the mk168 parts tester leads just on the left and center pins (gate and drain), I get a capacitor with either 2652pF or 1947pF depending on orientation of the leads.
If I place the leads on the left and right outer pins (gate and source) I get a capacitor with either 3274pF or 3190pF depending on orientation of the leads.
If I place the leads on the center and right pins (drain and source) I get a diode with a diode with a Uf of 561mV and a C of 3.76n. I get the same...Leave a comment:
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Re: MOSFET mystery
My dmm is a fluke 115.
So you're saying connect a wire from g and s, and then connect the device to my tester just as I have it pictured in my previous post and press "test" button?...Leave a comment:
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Re: MOSFET mystery
I don't know why I didn't think of using my parts tester instead of my DMM (duh!), but here are pics. The pinout is as same in the data sheet for the the other brand of 26N40. Tester says it an N enhance mosfet.
But why, when I use my DMM, do I get no reading with negative dmm probe on source and positive probe on drain even after I "charge" the gate with the positive probe? I only get the .5v reading with positive probe on source and negative on drain. And no matter what I do, I can't seem to discharge the fet?...Leave a comment:
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Re: MOSFET mystery
Yes. Could be. It's just odd that they didn't short, which is the common fault, and they're measuring like P channel mosfets. Opposite polarity. And I can't discharge it....Last edited by JimBanville; 09-14-2023, 06:33 PM.Leave a comment:
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Re: MOSFET mystery
My question is why isn't it measuring like a N channel mosfet?...Leave a comment:
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