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Old 4th June 2005, 04:27 AM   #1
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Default M250 Parts Replacement Querry....

hi everyone....
'm just asking if anybody have tried replacing the m250 output transistor. the original output transistor MJ15024/MJ15025. 'm planning to replace the MJ15024/MJ15025 with MJL4281A(NPN)/MJL4302A(PNP). anybody comments and analysis for these particular replacement is it working? or not? thanks just waiting.... see you soooooon.





a_p_deguzman
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Old 4th June 2005, 04:15 PM   #2
anatech is offline anatech  Canada
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What brand is the M250??

Why not use the originals? They are available, or the TO-3 equiv's. The plastic case does not mount easily where TO-3's were.

-Chris
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Old 4th June 2005, 08:49 PM   #3
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I believe this is the amp to which he is reffering: http://www.astro.uu.se/~marcus/private/m250.html
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Old 4th June 2005, 09:25 PM   #4
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MJ15024/MJ15025 are Darlingtons, and 4281/4302 are standard bipolars. You can not do that without some other changes in driver stage.

Sorry! My mistake, they are not Darlingtons.
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Old 5th June 2005, 04:17 AM   #5
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hi,

if you are referring the attachment,
you are not wrong
the amp will operate happily with those devices you want to replace
with, assuming that there are no PCB layout errors
and also you are close or equal to those assigned biasing voltages.....



enjoy building you amps.......

rgrds,

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File Type: jpg m250voltref1.jpg (50.0 KB, 805 views)
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Old 5th June 2005, 07:32 AM   #6
AJT is offline AJT  Philippines
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mj15024/15025 are hermetic to3's what you propose are plastic types, they will work!
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Old 5th June 2005, 11:37 AM   #7
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some advantages of the MJL4281 and MJL4302's:

higher ft (transistion frequency)
higher hfe, that it can handle more current to load
and a very desirable SOA curve.......

so need not hesitate

rgrds,

macweb
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Old 5th June 2005, 11:57 PM   #8
AJT is offline AJT  Philippines
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Default very felxible circuit!

supply this with +/-35 volts rails and you can use 5pairs of 2n3055/mj2955 trannies which are dirt cheap in our country! 4modules in a bridge will give you more power!
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Old 6th June 2005, 12:01 PM   #9
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I have tried even +-85vdc with MJL4281's and MJL4302's
at 4ohm loads and forced cooling.......

rgds,

macweb
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Old 6th June 2005, 12:48 PM   #10
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Default m250

thanks hienrich and joan2 for your reply... thanks also hienrich for the schematic with voltage ref... anyway i already have the data sheet of mjl4281/mjl4302.... by the way have you tried mje15034/mje15035 as drivers for mjl4281/mjl4302? these two transistor mje15034/mje15035 rated as 350volts 50watts....
anyway soon ill be starting to build this m250 using these new set of transistors.... whatever problems incountered or outcome ill just post it here....

alan
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