Author Topic: Can anyone cross reference these zeners please?  (Read 1574 times)

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Offline Chris Wilson

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Can anyone cross reference these zeners please?
« on: July 06, 2013, 06:22:41 am »
Circuit is for a small (missing) board for a huge Farnell 60 volt, 50 Amp linear power supply. I have a smaller version that is complete and working, but the schematics are a bit different, although somewhat similar. I have got together most of the bits to build a new board, and will have it remote and not plugged into an edge connector strip, to keep board manufacture simple. There should be a small schematic attached, but I have the full size one at http://www.gatesgarth.com/supplies.jpg  The diodes in question are the three zeners. I can't find any data on these numbers. Maybe someone with a deeper understanding of the circuit can suggest equivalents? Thanks!
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                 Chris Wilson.
 

Offline Paul Price

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Re: Can anyone cross reference these zeners please?
« Reply #1 on: July 06, 2013, 06:34:06 am »
The part numbers give away their voltage identity, but the M56, but from the more complete schematic it is a 5.6V zener rather than a 56V zener the designation implies, but the two on the right are surely about 5W and 15V and need to be matched.
« Last Edit: July 06, 2013, 09:34:05 am by Paul Price »
 

Offline Chris Wilson

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Re: Can anyone cross reference these zeners please?
« Reply #2 on: July 06, 2013, 06:38:17 am »
Thanks Paul, is that enough info to source suitable substitutes? How can you tell the IZM15 is a 1 watt device? It may be a 1ZM15, the schematic is not that clear. Any way to ascertain the wattage of the 56 volt device? Or should I just choose something beefy? Cheers.
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                 Chris Wilson.
 

Offline Paul Price

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Re: Can anyone cross reference these zeners please?
« Reply #3 on: July 06, 2013, 08:03:58 am »
Now that I see the rest of the schematic, the MR56 is actually a 5.6V zener, 1W and setts the bias for the two 15V in series zeners.

For the 5.6V zener 1W would be fine, 10% tolerance.

The 15V zeners should also be at least 5% precise voltage tolerance and they may have to be closely matched in voltage at 150mA of test current from a collection of them. Since the 15V zeners are also part of a crowbar protection circuit, this is another reason the 15V voltages here might need to be precisely set. The 15V zeners may have to be 5 Watt zeners mounted on a heatsink.  Be advised, the 82 ohm at the collectors of the 2N3053's, needs to handle up 3 watts of power under overload conditions,and the pair of 39 ohms at the emitters (at least  1W)  and the 2N3053s will require a  heatsink.
« Last Edit: July 06, 2013, 09:47:35 am by Paul Price »
 

Offline Chris Wilson

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Re: Can anyone cross reference these zeners please?
« Reply #4 on: July 06, 2013, 08:28:48 am »
That's great Paul, thanks again. If you want to see the rest it's at http://www.gatesgarth.com/farnell/farnell.html  The scans aren't great, but should be readable. Have a good weekend :)
Best regards,

                 Chris Wilson.
 

Offline Paul Price

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Re: Can anyone cross reference these zeners please?
« Reply #5 on: July 06, 2013, 08:43:48 am »
I looked at the pictures, rough as they are, and I can see there are still some lights missing from this Christmas tree.
 


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