EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: kishbud on January 20, 2022, 10:57:48 pm
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Power supply repair but this one diode I cannot identify or locate online, hopefully someone knows!
Glass Diode Identification 15PP?
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likely ZD, zener diode
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Yes, thank you but what does the making 15PP stand for so I can find a replacement?
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Yes, thank you but what does the making 15PP stand for so I can find a replacement?
15V, 1W Zener?
A photo of the surrounding electronics may help.
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Out of interest, why is the diode suspect?
Or is this where you replace all diodes and electrolytes while working on a PSU, just in case? If that is the case, you could skip this one?
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Zener diodes usually have significantly higher Forward Voltage that standard rectifier diodes.
So if this diode is still working, put your meter in diode mode and measure a few standard diodes you know to be rectifiers.
They usually read in the 500mV to 600 mV ballpark.
A Zener will often read in the 700mV ballpark, making them quite easy to spot.
I would agree with others here that it looks quite likely this is a Zener.
Edit: You can nearly always measure these Forward Voltages in circuit, so you don't need to remove any of them to test.
Just get a handle on what a normal diode looks like and you will spot the Zener a mile away.
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The power supply has a 3 position POT from 4.5-8v output for driving a medical light, after the initial repair, the 4.5v stage worked just fine but the 6v stage fried the 100ohm resistor in under 3 seconds (circled in red). So I have another guy working on it and he's repaired it so the resistor no longer lets the goast out but has come to the conclusion it might be the Zener to get fully operational and asked for my help identifying the diode to try a replacement but wants to know exactly what type and rating.
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I'd check and make sure someone didn't accidentaly replace a diode with that 100 ohm resistor in the last two pictures.
There's 3 diodes to the right, and it's looking awfully close to a bridge rectifier pattern, maybe it's some auxiliary winding from the transformer getting rectified, then smoothed out by the capacitors to the right.
The 68 ohm chipped resistor looks like a minimum load resistor to me...
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Well, it is a switched PSU, so there should be one bridge rectifier should be on the primary side, and those diode's do look to be on the primary side, but not really between the filter and the capacitor. Anyway, some trace following may easily show if they are in a bridge configuration.
Say, slight tangent: Those yellowish X2 capacitors. They are not the infamous period appropriate RIFA's are they?
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Good question mariush but no I was the first to work on this and those are my pics of when the 100ohm resistor let the goast out and I replaced it.
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Cybermaus they certainly do look like those type of caps don't they.
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The diode part# is likely 1S prefix not 15... (many vintage Japanese diodes) however the letters PP seem very odd.
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=1s++diode&_sacat=0&LH_TitleDesc=0&_odkw=1s+germanium+diode&_osacat=0 (https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=1s++diode&_sacat=0&LH_TitleDesc=0&_odkw=1s+germanium+diode&_osacat=0)
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Zener diodes usually have significantly higher Forward Voltage that standard rectifier diodes.
So if this diode is still working, put your meter in diode mode and measure a few standard diodes you know to be rectifiers.
They usually read in the 500mV to 600 mV ballpark.
A Zener will often read in the 700mV ballpark, making them quite easy to spot.
I would agree with others here that it looks quite likely this is a Zener.
Edit: You can nearly always measure these Forward Voltages in circuit, so you don't need to remove any of them to test.
Just get a handle on what a normal diode looks like and you will spot the Zener a mile away.
Ever since I gave it to another guy to repair, he has pulled some components he felt were thermally compromised as well as the Zener which had numbers printed on it "15PP" but couldn't read without removal. I was under the impression to get the correct breakdown voltages it's best to remove a Zener?
FYI, I thought I would build this Zener identifier I came across from someone else's hard work. Also this link has probably the best Zener identification circuit I've seen yet, I'll probably build one for myself because of the amount of time I burn on this stuff, it will really pay off in the future.
https://content.instructables.com/ORIG/FGS/ZLGC/H1JU4CIV/FGSZLGCH1JU4CIV.pdf (https://content.instructables.com/ORIG/FGS/ZLGC/H1JU4CIV/FGSZLGCH1JU4CIV.pdf)
https://content.instructables.com/ORIG/FBE/4WF8/H1JU4CIY/FBE4WF8H1JU4CIY.zip (https://content.instructables.com/ORIG/FBE/4WF8/H1JU4CIY/FBE4WF8H1JU4CIY.zip)
Zip contains a BRD and SCH file and can be opened with these links.
Attached BRD file opens with http://www.extremecircuits.net/2009/12/eagle-layout-editor-free-download.html (http://www.extremecircuits.net/2009/12/eagle-layout-editor-free-download.html)
Attached SCH file opens with http://www.fileguru.com/apps/sch_file_viewer (http://www.fileguru.com/apps/sch_file_viewer)
Original link- https://www.instructables.com/Build-a-Zener-Diode-Identifier/ (https://www.instructables.com/Build-a-Zener-Diode-Identifier/)
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The diode part# is likely 1S prefix not 15... (many vintage Japanese diodes) however the letters PP seem very odd.
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=1s++diode&_sacat=0&LH_TitleDesc=0&_odkw=1s+germanium+diode&_osacat=0 (https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=1s++diode&_sacat=0&LH_TitleDesc=0&_odkw=1s+germanium+diode&_osacat=0)
That's a great observation, unfortunately I'm not in possession of the unit to confirm that, maybe he has a photo from when he removed it, I'll ask. Thanks!
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If the zener (assuming it is a zener) is bad I'll hazard a guess it won't breakdown the way it's supposed to (bad diodes usually short out). You'll have to reverse engineer the circuit around it and make an educated guess.