EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: strtfr on February 16, 2018, 06:41:05 pm
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Does someone know what the part with one leg disconnected is? Apparently some sort of diode I guess. It is connected to a SMT fuse and has 1 - 1 - 1 markings on it. Its neighbor has 9 - 9 - 9 (6 - 6 - 6?) markings on it. I'm not familiar with this part, does someone know a (regular) substitute or number?
(https://i.imgur.com/qgfGsrO.jpg)
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Any other markings you may have missed on? Ideally, you'd be best removing the diode for having a proper inspection with a magnifier.
Also, it might help if you'd provide the make/model of the particular device the circuit belongs to.
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It's a MELF diode.
A substitution trick is to bend a leaded equivalent replacement leads under so they're able to reach/connect with the pads.
Unless space is tight and you can't get at the pads from the side. But sometimes a true SMD equivalent is available and in say a gullwing package
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It sure is a diode as is marked "D2".
Those cilindrical diodes are funny because they roll.
You say that it is next to a fuse.
It could help to know in which side of the fuse it is: after or before the power input.
Also will help to know where the other pin goes.
It could be a protection that burns the fuse when you reverse power the circuit. But, as you know, Murphy law says that a device burns faster than the fuse that protects it.
It could be also a series protection diode to prevent the same fault although it adds a Vd drop. But, in this case, it is not easy to fail as you show.
Is if it this kind of diode, I think that you can work out a substitution from is intended functionality.
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Any other markings you may have missed on? Ideally, you'd be best removing the diode for having a proper inspection with a magnifier.
Also, it might help if you'd provide the make/model of the particular device the circuit belongs to.
Thank you. The only markings it has on its package are:
1
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1
-
1
In a circular motion.
The PCB is from a small local HAVC manufacturer. The company has filed bankruptcy some time ago and the curator won't provide warranty or sell me any new devices. I've to ask my friend for this manufacturers name.
It's a MELF diode.
A substitution trick is to bend a leaded equivalent replacement leads under so they're able to reach/connect with the pads.
Unless space is tight and you can't get at the pads from the side. But sometimes a true SMD equivalent is available and in say a gullwing package
Thank you. The pad at the disconnected lead is destroyed and the track is intermitted. I'm not sure what happened first, strong oxidation or high temperature problems.
It sure is a diode as is marked "D2".
Those cilindrical diodes are funny because they roll.
You say that it is next to a fuse.
It could help to know in which side of the fuse it is: after or before the power input.
Also will help to know where the other pin goes.
It could be a protection that burns the fuse when you reverse power the circuit. But, as you know, Murphy law says that a device burns faster than the fuse that protects it.
It could be also a series protection diode to prevent the same fault although it adds a Vd drop. But, in this case, it is not easy to fail as you show.
Is if it this kind of diode, I think that you can work out a substitution from is intended functionality.
Thank you. This part is behind the fuse and before a small packaged rectifier. Not sure, I have to look again this evening. The other lead is connected to one side of D8, the diode with 9 | 9 | 9 on it.
I have found this part:
http://ly.rsdelivers.com/product/nxp/prll5817/nxp-prll5817-smt-diode-20v-1a-2-pin-melf/4843592 (http://ly.rsdelivers.com/product/nxp/prll5817/nxp-prll5817-smt-diode-20v-1a-2-pin-melf/4843592)
It is a Schottky barrier diode with the same markings as D8 ( 9 9 9 ) on it.
http://pdl.designspark.com/api/v1/manufacturers/53f31a719b4759f8698bcb56/part/5528bfbf9b47596818a284d4/5528bfc09b47596818a284f8/1pdf (http://pdl.designspark.com/api/v1/manufacturers/53f31a719b4759f8698bcb56/part/5528bfbf9b47596818a284d4/5528bfc09b47596818a284f8/1pdf)
Now I have to find what this (1 1 1) means.
I'll will do some searching and testing this evening and report back.
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I've done some haphazard research and apparently it is an SOD87 diode from Philips / NXP.
I have found its type number in this PDF. Just search for 1-1-1.
http://zxevo-files.perestoroniny.ru/datasheets/www.nxp.com/documents/other/SC11_MARKING_4.pdf (http://zxevo-files.perestoroniny.ru/datasheets/www.nxp.com/documents/other/SC11_MARKING_4.pdf)
Which leads me to the BYD17 product sheet.
https://media.digikey.com/pdf/Data%20Sheets/NXP%20PDFs/BYD17.pdf (https://media.digikey.com/pdf/Data%20Sheets/NXP%20PDFs/BYD17.pdf)
It's a General purpose controlled avalanche rectifiers.
Again thank you all.
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There's nothing special about the specs for these diodes and just for a try, jellybean similar diodes is what I'd chuck in to check it all works first then get the correct ones later for a better and hopefully long lasting repair.
If you not constrained for height pretty much any similar spec leaded part should do for a try.