I have a pretty hefty power supply that let the smoke out, inside I found diodes that had failed open. Admittedly most of the diodes had burnt and cracked in half or blown up. Your tip is good and much appreciated! It’s a good way of getting at least a preliminary overview of the problem.
To add to your consensus. I just had a diode go bad in a welding machine and it had direct continuity with less than 1 ohm resistance , it shorted internally.
Thanks Dave. I check diodes as well as transistors etc., with my BK Precision 114A VOM using resistance, which also on 10K gives a 12V insulation test.
Hey old friend. I've been wondering where you've been the last year or so. I'd be glad to see you again if you're in this area, and to do a little catching up.
Yes, I've had silicon diodes open, short, and be leaky (lower than normal forward or reverse resistance). The leaky ones are the toughest to figure out because the instances are so few. Open diodes are much less common today than they were in equipment of the 1960s and 1970s. I spent hours on a Toshiba tube TV once with an open rectifier in series with the line in half wave config. Even though my VOM was telling the truth, I didn't want to believe it! It's been 35 years since I've done significant troubleshooting on a regular basis. This is before the existence of diode functions in digital multimeters. Heck, it's almost before the existence of digital multimeters!
Excellent tip, BTW!! I'M not sure everybody gets the fact that the reading you get on the diode function is the voltage drop across the semiconductor. This makes it great for leak testing if you know what readings to expect at a given semiconductor junction.
Thanks walt. Other than seeing diodes that were blown apart, I can only remember one instance where a diode checked good with my meter, but failed to work in the circuit.
interesting. I was reading the comments and what you guys are saying is interesting. my question is what was the fix grant for this diode you found it good with the multimeter and its failed in the circuit?
Hi Dave. Hope your well. Tim here in UK. All TV repair work dried up here. Just getting non stop sets with burnt out led backlights. Usually taking out power supply fets too. This likely will be my last year in TV repair. Real shame after 28 years. But it's all just junk now.
Hi Tim,. Same situation for me here in the USA.. Were it not for TV antennas, TV hook ups, Customer errors and miscelanous projects that I've been doing on the side,, I would have had close my doors already..
I am working on that exact board that you have there I even paused the video and yeah, it’s the same board, my TV has no back lights and I’m trying to figure it out👍🏻🇺🇸
What if there are a bunch of diodes sharing positives and negatives, the whole positive for example would show a short but probably only one of the diodes is bad, is there a way to check them in circuit?
Diodes generally shot out when they go bad, so if you're seeing OL in one direction but not when you switch leads that generally indicates the diode is good, but I suggest using the diode test function on your multimeter.
At 1:46 you test the diode on resistance mode and you say, it reads 1.61 Ohms [and with the leads reversed, you get 1.59] and you say, it’s not really picking up the diode, it’s picking up the coil? Well then, how do you know if the diode is good or bad, since the multimeter is not reading the diode. Pardon my ignorance, I’m a baffled NOOB, but I want to learn. Cheers!
The point I was making in this video, is bad diodes generally short out when they go bad, and every shorted diode I've ever tested on my ohmmeter showed one ohm or less when testing them on my multimeters resistance scale. If the diode isn't shorted you're not going to get any reading at all using the resistance scale on most multimeters. The 161 ohms or 159 ohm reading only showed the resistance of the relay coil because it was in parallel with the diode, but if the diode had been shorted the resistance reading would have showed one ohm or less on the resistance scale.
@@GrantsPassTVRepair Thank you for replying, I truly appreciate it. Ok? But I’ve tested a bunch of diodes [after watching this video - out of circuit] I couldn’t find a bad/shorted diode, so I tested what I had [all good diodes] and on resistance mode, and I did get readings one way +/-132 Ohms, +/-162 Ohms or whatever BUT I got OLs the other way, and I did this with a El Cheapo multimeter, nothing fancy at all. So I find it curious, I mean why, wouldn’t a multimeter pick up the Ohmic value of a diode, when it’s in parallel with another component? And why WOULD it, when a diode is shorted? Can you explain why that would be, is it a limitation of the multimeter - is there a reason? Please let me know, if you find anything. And thanks again for replying. Cheers!
@@maxwarfield6699 The reason is most digital multimeters don't put out enough voltage on the resistance scale to test a diode. That's why they add a diode test function which does put out a higher voltage. The older style analog multimeters put out a higher voltage on the resistance scale but not the digital meters. If you're still confused you can call me
Hello. I would like to ask if its possible to check the "Schottky barrier diodes" in atx power supply in circuit without desoldering. It would be a great help to me hearing your advice.. Thank you.
Hello...newbie troubleshooter here. I was testing a diode (on diode mode on the meter) in a cb radio. It was giving a reading going both ways so I thought it was bad so I unsoldered it and removed it. Once it was removed I tested it again and the thing tested fine. So...if I'm testing a diode still in circuit, you're saying the resistance (ohm) setting would be better?
@@GrantsPassTVRepair Thank you! That will help me out a lot knowing that. I appreciate you writing back, too. I've asked some people in other "repair" videos that never write back.
Im confused reading the diode of my board, its connected to the primary side and 2nd side but it reads short same as what u did with the diode connected to relay, but when i took out the diode it reads fine not short. What could be?
Hi, I jumped into this video as I was trying to understand the typical 'TV repair kit' which are sold lately online, in particular on Vestel power board. I am talking about those 6 diodes pack which need to be replaced when LCD backlight does not switch on properly. The question is: even though a diode is tested with forward and inverse direction current and the result is good, is it possible that they start to be insufficient for their duty? like a resistor which heats up or a capacitor which is exhausted under current? Thx
Finding diodes that test okay on your meter but don't operate correctly when they have power running through them has been extremely rare in my experience. I can only remember seeing this happen once in the 26 or 27 years I've been servicing commercial electronic equipment. .
Hi again, I have another question. The one ohm or less, would that matter which way you have the test leads on it or would it show one ohm or less going both ways?
@@GrantsPassTVRepair I still don't know what I'm doing I guess. I found one that tested .9 something so I removed it with a "good" diode. Once the good diode was soldered in place it gave me the same reading.
If your Diode checked .9 and you're on the ohms scale of your meter that sounds like a short, but keep in mind There can be other components in parallel with the Diode you're testing which make a good diode appear shorted. That's why I suggest using the ohms scale so you can find out what the actual resistance is, You could have also tested the diode you removed using the diode check function of your multi meter, and it would have revealed if there was a problem or not. Checking a Diode is very simple. If my video did not explain it well enough there are probably hundreds more that will.
No, I'm checking for the opposite of infinite resistance. I'm checking for shorts, meaning the diode went bad, and now it's more like an ordinary piece of wire with almost no resistance,. Usually less than an ohm.
@@GrantsPassTVRepair If the diode has negligible resistance when working correctly, does this mean you need to know the expected resistance of the coil in order to determine if the diode is adding something on top? Thanks for the reply!
As a general rule the relay coils you find in TVs will be way above one ohm, so if you happen to be checking the a diode which is in parallel with a relay coil ,and it doesn't read less than One ohm or less, it's most likely a good diode.
chinese devices had these open diode problems on the psu , love your videos, been out of the game for almost a decade now, just fixing my own device or friends gadgets,, but because of this pandemic im currently acquiring tools for the trade again,, im so stressed with whats happening in this big cities
From what I've been seeing in this area covid hasn't been much of an issue for healthy people. Out of 36 peopple I know who have had it only one died, and she was a diabetic, overweight and at to much junk food.
I have a pretty hefty power supply that let the smoke out, inside I found diodes that had failed open. Admittedly most of the diodes had burnt and cracked in half or blown up.
Your tip is good and much appreciated! It’s a good way of getting at least a preliminary overview of the problem.
Thanks! I’m going to test my blower motor resistor tonight and wasn’t sure how to do it while connected to a board
Yes, I've done this as well, sometimes you can go crazy checking diodes, especially schotky diodes..!!
To add to your consensus. I just had a diode go bad in a welding machine and it had direct continuity with less than 1 ohm resistance , it shorted internally.
Thanks Dave. I check diodes as well as transistors etc., with my BK Precision 114A VOM using resistance, which also on 10K gives a 12V insulation test.
Good to see you out there Dave, Maybe on my next excursion to Oregon i will have to stop by for another visit.
Hey old friend. I've been wondering where you've been the last year or so. I'd be glad to see you again if you're in this area, and to do a little catching up.
Yes, I've had silicon diodes open, short, and be leaky (lower than normal forward or reverse resistance). The leaky ones are the toughest to figure out because the instances are so few. Open diodes are much less common today than they were in equipment of the 1960s and 1970s. I spent hours on a Toshiba tube TV once with an open rectifier in series with the line in half wave config. Even though my VOM was telling the truth, I didn't want to believe it! It's been 35 years since I've done significant troubleshooting on a regular basis. This is before the existence of diode functions in digital multimeters. Heck, it's almost before the existence of digital multimeters!
My VOM is a BK Precision 114A in mint condition. I never doubt it.
Excellent tip, BTW!! I'M not sure everybody gets the fact that the reading you get on the diode function is the voltage drop across the semiconductor. This makes it great for leak testing if you know what readings to expect at a given semiconductor junction.
Thanks walt. Other than seeing diodes that were blown apart, I can only remember one instance where a diode checked good with my meter, but failed to work in the circuit.
interesting.
I was reading the comments and what you guys are saying is interesting.
my question is what was the fix grant for this diode you found it good with the multimeter and its failed in the circuit?
Grants Pass TV Repair It probably would have failed an insulation test, maybe even with a VOM on 10K.
Hi Dave. Hope your well. Tim here in UK. All TV repair work dried up here. Just getting non stop sets with burnt out led backlights. Usually taking out power supply fets too. This likely will be my last year in TV repair. Real shame after 28 years. But it's all just junk now.
Hi Tim,. Same situation for me here in the USA.. Were it not for TV antennas, TV hook ups, Customer errors and miscelanous projects that I've been doing on the side,, I would have had close my doors already..
@@GrantsPassTVRepair have a good Christmas Dave. I hanging on till December but new year looking to set up gardening maintenance business .
@@MrBilbo44uk Same to you Tim, I hope you find your greatest potential.
Hi..hello.. thanks alot.. great teacher ..really i learn more from you all vedio series.... Thanks Thanks so much ..teacher ..
Ali.from.sudan.
Thanks for the comment. All the best
I am working on that exact board that you have there I even paused the video and yeah, it’s the same board, my TV has no back lights and I’m trying to figure it out👍🏻🇺🇸
I think the same. Hard to conclude if a diode has gone bad
I remember some late 80's Korean made VCR's having open diodes in their power supplies.
I have only seen diodes go open circuit when they are physically blown apart.
What if there are a bunch of diodes sharing positives and negatives, the whole positive for example would show a short but probably only one of the diodes is bad, is there a way to check them in circuit?
Great video! One question, what if I do get over 1 ohm from one side, but if I switch leads I get OL? Does that mean it’s a bad diode? Thanks
Diodes generally shot out when they go bad, so if you're seeing OL in one direction but not when you switch leads that generally indicates the diode is good, but I suggest using the diode test function on your multimeter.
@@GrantsPassTVRepair thanks for answering my questions.
good tips
At 1:46 you test the diode on resistance mode and you say, it reads 1.61 Ohms [and with the leads reversed, you get 1.59] and you say, it’s not really picking up the diode, it’s picking up the coil? Well then, how do you know if the diode is good or bad, since the multimeter is not reading the diode. Pardon my ignorance, I’m a baffled NOOB, but I want to learn. Cheers!
The point I was making in this video, is bad diodes generally short out when they go bad, and every shorted diode I've ever tested on my ohmmeter showed one ohm or less when testing them on my multimeters resistance scale. If the diode isn't shorted you're not going to get any reading at all using the resistance scale on most multimeters. The 161 ohms or 159 ohm reading only showed the resistance of the relay coil because it was in parallel with the diode, but if the diode had been shorted the resistance reading would have showed one ohm or less on the resistance scale.
@@GrantsPassTVRepair Thank you for replying, I truly appreciate it. Ok? But I’ve tested a bunch of diodes [after watching this video - out of circuit] I couldn’t find a bad/shorted diode, so I tested what I had [all good diodes] and on resistance mode, and I did get readings one way +/-132 Ohms, +/-162 Ohms or whatever BUT I got OLs the other way, and I did this with a El Cheapo multimeter, nothing fancy at all. So I find it curious, I mean why, wouldn’t a multimeter pick up the Ohmic value of a diode, when it’s in parallel with another component? And why WOULD it, when a diode is shorted? Can you explain why that would be, is it a limitation of the multimeter - is there a reason? Please let me know, if you find anything. And thanks again for replying. Cheers!
@@maxwarfield6699 The reason is most digital multimeters don't put out enough voltage on the resistance scale to test a diode. That's why they add a diode test function which does put out a higher voltage. The older style analog multimeters put out a higher voltage on the resistance scale but not the digital meters. If you're still confused you can call me
Hello. I would like to ask if its possible to check the "Schottky barrier diodes" in atx power supply in circuit without desoldering. It would be a great help to me hearing your advice.. Thank you.
Thanks to an under dimensioned diode bridge once I nearly burned my house.
Hello...newbie troubleshooter here. I was testing a diode (on diode mode on the meter) in a cb radio. It was giving a reading going both ways so I thought it was bad so I unsoldered it and removed it. Once it was removed I tested it again and the thing tested fine. So...if I'm testing a diode still in circuit, you're saying the resistance (ohm) setting would be better?
Yes I suggest it's a more reliable way to test a diode without having to remove it since most diodes that have shorted out will read One ohm or less.
@@GrantsPassTVRepair Thank you! That will help me out a lot knowing that. I appreciate you writing back, too. I've asked some people in other "repair" videos that never write back.
Sorry but could you tell me what resistance mode is can’t see on video great vid still I like your diode list 😀
It sounds like you need to find a video on how to use your multimeter.
Most flat screens tv in uk are worth more in parts then repairing or selling the set....
Im confused reading the diode of my board, its connected to the primary side and 2nd side but it reads short same as what u did with the diode connected to relay, but when i took out the diode it reads fine not short. What could be?
To chech a diode. Is it compulsory to remove from a circuit first
In some circuits it might be necessary to removed the diode to test it, but in most circuits you don't need to remove them.
does it work for smd sot23 diodes? (zener) i mean testing in resistence mode and look for resistencer around 1Ohm
I see lots of lower end Vestel re-badges with shorted PSU secondary diodes.
Hi, I jumped into this video as I was trying to understand the typical 'TV repair kit' which are sold lately online, in particular on Vestel power board. I am talking about those 6 diodes pack which need to be replaced when LCD backlight does not switch on properly. The question is: even though a diode is tested with forward and inverse direction current and the result is good, is it possible that they start to be insufficient for their duty? like a resistor which heats up or a capacitor which is exhausted under current? Thx
Finding diodes that test okay on your meter but don't operate correctly when they have power running through them has been extremely rare in my experience. I can only remember seeing this happen once in the 26 or 27 years I've been servicing commercial electronic equipment. .
Sir.. if diode explodes in psu.. does it damage the mothetboard or not?
Based on my experience a bad diode in the power supply is not likely to damage the motherboard,
@@GrantsPassTVRepair thanks for the response. Ill test it out if i buy a new psu
Hi again, I have another question. The one ohm or less, would that matter which way you have the test leads on it or would it show one ohm or less going both ways?
If the Diode is shorted it will not matter which way you have your test leads.
@@GrantsPassTVRepair I still don't know what I'm doing I guess. I found one that tested .9 something so I removed it with a "good" diode. Once the good diode was soldered in place it gave me the same reading.
If your Diode checked .9 and you're on the ohms scale of your meter that sounds like a short, but keep in mind There can be other components in parallel with the Diode you're testing which make a good diode appear shorted. That's why I suggest using the ohms scale so you can find out what the actual resistance is, You could have also tested the diode you removed using the diode check function of your multi meter, and it would have revealed if there was a problem or not. Checking a Diode is very simple. If my video did not explain it well enough there are probably hundreds more that will.
Not sure I understand. Are you checking for infinite resistance to indicate that the diode has failed open?
No, I'm checking for the opposite of infinite resistance. I'm checking for shorts, meaning the diode went bad, and now it's more like an ordinary piece of wire with almost no resistance,. Usually less than an ohm.
@@GrantsPassTVRepair If the diode has negligible resistance when working correctly, does this mean you need to know the expected resistance of the coil in order to determine if the diode is adding something on top? Thanks for the reply!
As a general rule the relay coils you find in TVs will be way above one ohm, so if you happen to be checking the a diode which is in parallel with a relay coil ,and it doesn't read less than One ohm or less, it's most likely a good diode.
my tv has a similar problem bt in my case the remote only turns on the tv and it functions no more..cud you be of assistance???
Similar problem as?
it does not recognise the remote command except the power button only
Perhaps you might find my video on remote control repair helpful. ua-cam.com/video/xvJWqf_b6Eo/v-deo.html
chinese devices had these open diode problems on the psu , love your videos, been out of the game for almost a decade now, just fixing my own device or friends gadgets,, but because of this pandemic im currently acquiring tools for the trade again,, im so stressed with whats happening in this big cities
From what I've been seeing in this area covid hasn't been much of an issue for healthy people. Out of 36 peopple I know who have had it only one died, and she was a diabetic, overweight and at to much junk food.
@@GrantsPassTVRepair Type 2 diabetic I assume
@@TWIRKNOLOVE I'm not sure,
They open under extreme current conditions
Helpful
What replaces a 5408gr pn
Seen diodes go short, leak, or open . . .
"CONCERTA" like the Portuguese word that means "to fix"!?
is there any groups on facebook to help me