Unknown diode, need help identifying.

Thread Starter

4Realb

Joined Jun 1, 2018
3
I have this control module from a New Holland tractor that's not working. I need to identify the diode pictured to find a replacement, and I'm wondering if anyone has seen such a part before and knows what it is. I have not been able to find anything on the internet so far, but I'm also not even sure that i'm searching for the correct item or using correct terminology. It is the blue and white egg shaped one in the middle of the picture. Thanks everyone!
 

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-live wire-

Joined Dec 22, 2017
911
Do you have a multimeter? If so, try measuring the diode's fV with it. If it does not have that functionality, try measuring the voltage drop when taken out and put in a resistor circuit. Use whatever DC power supply you have available and use a high value resistor to limit the current to a few milliamps. If it gives you weird readings in the circuit, try removing it. If it becomes apparent that the problem is not the diode, look for other visible damage.
 

Thread Starter

4Realb

Joined Jun 1, 2018
3
Yeah...I have no problem finding videos on youtube on how to troubleshoot a diode. What I would like to find out is what type of diode it is, where it came from (manufacturer), what the specs for it are, are replacements availble, etc.

If anyone has seen one like this, spherical, ceramic bodied, with colored bands and dots, and has an info on their construction/specifications, that would be most helpful. Thanks!
 

ian field

Joined Oct 27, 2012
6,539
It could be a shottky, primary reason i'd like to be able to identify it and find specs for it.
Those ones with no number are a pain - you may have to make a best guess.

As someone else suggested, it could be Shottky barrier - but those are more likely to have proper numbers.

Its a popular package style for fast soft recovery types - but standard 50/60Hz rectifiers aren't exactly rare.

If it isn't blown - some out of circuit testing will solve a couple of mysteries - SB have a markedly lower Vf for example.

A service manual is always nice - but you might need to do some hand tracing before that "best guess".
 

ebp

Joined Feb 8, 2018
2,332
It is hard to tell from the photo, but I get an impression that perhaps the diode is for reverse polarity protection for power to the circuit board. That impression comes from surrounding components such as capacitors that might be noise filters, the fact it is D1 and the proximity to a connector.

It might be a Schottky diode or just an ordinary silicon PN junction diode. I also think a current rating of 3 A is reasonably likely. If it is for reverse polarity protection and it has failed, there are many diodes that could be used as replacements.

Glass packaged diodes like that used to be much more popular than they are now. They tend to be considerably more expensive than plastic packaged diodes, though still quite cheap.

~~~
"A service manual is always nice..."
I don't know about New Holland, but some farm machinery manufactures have made it essentially impossible for owners to get any sort of documentation. They want to sell high-priced maintenance contracts. Even where documentation is available, details of circuitry are unlikely to be included. Instead you get told "replace module" - which wouldn't be too terrible if a new on were fifty or a hundred dollars.
 

ian field

Joined Oct 27, 2012
6,539
It is hard to tell from the photo, but I get an impression that perhaps the diode is for reverse polarity protection for power to the circuit board. That impression comes from surrounding components such as capacitors that might be noise filters, the fact it is D1 and the proximity to a connector.

It might be a Schottky diode or just an ordinary silicon PN junction diode. I also think a current rating of 3 A is reasonably likely. If it is for reverse polarity protection and it has failed, there are many diodes that could be used as replacements.

Glass packaged diodes like that used to be much more popular than they are now. They tend to be considerably more expensive than plastic packaged diodes, though still quite cheap.

~~~
"A service manual is always nice..."
I don't know about New Holland, but some farm machinery manufactures have made it essentially impossible for owners to get any sort of documentation. They want to sell high-priced maintenance contracts. Even where documentation is available, details of circuitry are unlikely to be included. Instead you get told "replace module" - which wouldn't be too terrible if a new on were fifty or a hundred dollars.
When my Hitachi CD/DAB packed up - they didn't even know if there was any such thing as a service manual. Figured it out eventually - since won an identical unit badged as one of the Argos brand (still not found out who actually manufactured it). Looks like the same fault as the one I bought, handy for spares - except the previous owner destroyed the cassette flap getting their tape out.
 
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