• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

What am I ?

Status
Not open for further replies.

bryan

Member
Hello:

Repairing a pcb for a Aquarium controller. No power is being received at the input of a 7805 voltage regualtor. I am positive the component in the picture is faulty. Bypassing the component and everything works as it should. Only markings are 27N. i believe it is a zener diode? Any ideas of a mfg part number.
 

Attachments

Sceadwian

Banned
Regular Diode. Clamp maybe?
 

Mickster

Well-Known Member
Most Helpful Member
Can't find a 27N in the code books I have, but 27V is listed as a 27V Zener in a SOT346 package..

Will have another poke around and see what comes up, if anything.
 

Sceadwian

Banned
I'd got with Mickster.
 

bryan

Member
Thanks all. i did stumble upon the PZM27N, but could not figure out why it would need a 27v zener, so thought this can't be it. I am going to map out the traces around the area in a schematic and post. Perhaps it may be more useful in determining what it is used for. Only think i can think of the zener is to protect the 7805 from a spike or a faulty wall transormer should it put out more than 27volts.
 

Pommie

Well-Known Member
Most Helpful Member
If it's a protection zener then bypassing it should short out the power supply.

Mike.
 

bryan

Member
With 3 legs? there is other smd caps nearby and they are all the expected SMD types. But worth a look. Thanks.
 

mvs sarma

Well-Known Member
With 3 legs? there is other smd caps nearby and they are all the expected SMD types. But worth a look. Thanks.
Sorry - Didn't watch the centre pin on the other side.
it is philips make 27V zener diode.
it is listed on the right side of page 2 of datasheet attached.
Nice that Mickster already did it well ahead of me
 

Attachments

Last edited:

bryan

Member
Hi All:

Put in a e-mail to the mfg and they were kind enough to reply back. they say it is a regular diode. Have to question the markings though as it points to a zener. Mfg states the diode is not required but is there for noise immunity. I replaced it with a spare 1N4004 I had around and it works fine. Put in another e-mail to see if they will disclose the actual mfg part number so I can do a direct replacemnt.

Will post up a schematic later tomorow, hard to see where all the traces go because it is a double side board and the silkscreen makes it hard to follow.
 

bryan

Member
All:

Here is the schematic around the area of the unknown components. I am beginning to think they are just regular diodes.
 

Attachments

Leftyretro

New Member
Looks like they are a pair of diodes used to isolate the normal power input from the battery power input. Most likely low forward voltage drop Schottky type, but didn't know they came in 3 terminal packages, two of the terminals much to electrically the same.

Lefty
 

bryan

Member
The battery does not get charged, it is not rechargeable. the micro will display a low battery warning on the LCD. But I can not figure out how the micro knows when the battery is low.
 

mvs sarma

Well-Known Member
The battery does not get charged, it is not rechargeable. the micro will display a low battery warning on the LCD. But I can not figure out how the micro knows when the battery is low.
why not effort to pu more detailed schematic than the power part alone. May be, that they took a potential divider based input from the battery for measuring its voltage by the Micro !!
 

bryan

Member
Difficult to read the board. It is double sided and silked on one side. Traces are super thin and hard to follow with all the vias. But the good s news is I substituted a 1N4004 diode that I had in the parts box and it is working fine.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top