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Replacing zener diode help

T

theokalat

Active Member
Hi folks,

I need to replace a zener diode in my Yamaha MX-1.
The part in question is MTZJ3.0A.

I assume it is 3 volts and 1/2 watt rating.

I cannot get an exact voltage replacement, but the closest match my local supplier has is a 2.7v and a 3.3v zener.

Now my question is, how critical is the voltage rating, if not critical, should I be going for the 2.7v or 3.3v zener in this case.

Thanks in advance for any assistance given.
 
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Usually a zener is used to set a specific voltage. It can be used in a clipper or clamper circuit to set the voltage of a waveform. Considering you have one at 3V and see others with slight variations at 2.7V and 3.3V, this is pretty much saying this circuit needs 3V. A quick google search found several 3V zeners at different power ratings from .05W - .5W. You should be able to find what you need.
 
avionic said:
MTZJ3.0
2.8v - 3.2v
500mw
Click to expand...

I was a bit worried the deviation in voltage was too much with the 2.7 and 3.3.

Since the diodes from my local supplier fall outside the recommended range, I will have to source the diodes elsewhere to meet the specs.

Cannot buy from mouser or DK as the shipping costs of roughly $30 for one diode makes it uneconomical to Sydney.
DK offers free international shipping only if the total purchase exceeds $200.



Thanks to everyone for their valuable assistance in sorting this out for me.
 
Last edited:
I just popped down to my local supplier and picked up 2 each of the 2.7 & 3.3 volt 1/2watt zeners.

I put them through the diode test on my DMM, they all showed between 600-650 one way.
When I switched leads around, I expected no reading consistent for a good diode, BUT all four showed a reading which is not what a good diode would do.

Other new diodes I purchased but of a higher voltage were good, so I think these four maybe faulty. Maybe 1 or 2 at most, but all four! That is a worry.

Same results using another DMM. So cannot be my DMM being faulty.

If anyone has any new 1/2 watt zener diodes of low voltage of between 2 and 3.3 volts handy on their bench, can you please do the diode test with your multimeter and see if you get a reading or not after switching leads around.

Same results using another DMM.

I am just wondering whether it is normal for small value zener diodes to show a reading somewhat.

Any opinions are welcome as to what could be the issue with these diodes appreciated.
 
Last edited:
Stand-by ---zeners test weird with a standard DMM.

3 volt zener----------

Fluke 179 diode test
750mv/ 2.33v
 
Last edited:
Actually you can just measure the zener voltage in circuit.
 
Yes they will measure both ways. (ohms) if I recall (I have a full range hanging on the wall right here if I wanted to check (lazy).
but I think when they hit a certain value going up, they will stop reading in both directions.
 
avionic said:
Stand-by ---zeners test weird with a standard DMM.

3 volt zener----------

Fluke 179 diode test
750mv/ 2.33v
Click to expand...


I got similar readings to yours. So there probably is no need for concern with the zeners I bought.

I find only the low voltage zeners test funny, whereas the higher voltage zeners test like normal diodes with a DMM.

Thanks Avionic.

I can now use these diodes knowing they are good to go.
 
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