Part sub for MOSFET gurus

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ilimzn

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Joined 2005
You will not find the datasheets because you have mixed up the numbers, it is 2SJ56 and 2SK176.
The MTP MOSFETSs you reference will most certainly NOT be proper replacements, becase the parts used in Hafler amps are Hitachi/Renesas lateral types which do not require thermal compensation and have a low treshold voltage, whereas the Fairchild ones are high treshold vertical MOSFETs which will go into thermal runaway without proper thermal compensation. There are a number of other differences, not the least of which is different pinout (originals have the Source on the case, your proposed ones have the Drain).
HItachi/Renesas still manufactures these devices uned different names because the case has changed. They now use plastic TO3P type cases instead of the old style metal TO3 variant, but the new ones can be adapted to old style heatsinks with minor work, when the new one's pins are bent to 90 degrees, they fit the original footprint.
The closest easily obtainable ones are 2SJ162/2SK1058, these are however 7A parts instead of the original 8A. If you invest in a few more units the difference may be moot assuming you find adequate matched pairs to put in parallel.
There is also 2SJ352/2SK2221 which are improved replacements for your originals, but these are usually hard to find and quite expensive.
Originals are still available ta rather high prices. They can also be had on eBay, but as usual - buyer beware.
 
Ian Finch

Ian Finch

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Joined 2010
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Or...You could direct substitute with SEMELAB ALF08N20K / ALF08P20K obtainable from their agent or Newark or Magnatec in the UK. They are 8 amp parts and have the Source connected to the case so as to substitute for original Hitachi parts. Note the original parts and these have a body diode connection which is not fitted in TO3-P /TO247 substitutions where you'll need to add a zener arrangement to suit most other, newer Lateral MOSFETs. These are not VFETs.
Watch your wallet get very slim in any event, though.
 
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djk

djk

R.I.P
Joined 2001
Since you can't be bothered to read the spec sheet he linked to, I will tell you that it links to a vertical device with a high threshold voltage which requires thermal compensation.

Why don't you ask him what amplifier he is trying to repair?

You might also tell him that the pin outs of the lateral parts he was asking about are different, as well as the bias requirements.

" > > Hello Group,
> > Does anyone have stock or replacements
> > for the MTP20N10 and MTP20P10
> > output transistors for a SUMO Andromeda II.
> > I realize they are discontinued fet's.
> > I have datasheets for one of the devices
> > but have found no substitutes.
> > I've searched high and low with no success.
> > Any information at all will be greatly appreciated.
> > Would the TO3 2SK176 and 2SJ56 be suitable?
> >
> > Thanks
> >
> > Jim"
 
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IFixAudio

IFixAudio

Member
Joined 2007
So...
What I gather so far here is that the IRFP240 and IRFP9140 should do the trick???
The SEMELAB ALF08N20K / ALF08P20K will not work? They are advertised as audio fets and are even in TO3 cases.
Sorry for the trouble to the group, I am a great tech but do not do well trying to interpret and interrelate MOSFET specs to replace 25 year old devices with something modern.

Thanks again

Jim
 
I

ilimzn

Member
Joined 2005
djk said:
Since you can't be bothered to read the spec sheet he linked to, I will tell you that it links to a vertical device with a high threshold voltage which requires thermal compensation.
Why don't you ask him what amplifier he is trying to repair?
You might also tell him that the pin outs of the lateral parts he was asking about are different, as well as the bias requirements.

" > > Hello Group,
> > Does anyone have stock or replacements
> > for the MTP20N10 and MTP20P10
> > output transistors for a SUMO Andromeda II.
> > I realize they are discontinued fet's.
> > I have datasheets for one of the devices
> > but have found no substitutes.
> > I've searched high and low with no success.
> > Any information at all will be greatly appreciated.
> > Would the TO3 2SK176 and 2SJ56 be suitable?
> >
> > Thanks
> >
> > Jim"
Click to expand...

I did read the datasheet, but you are right, I didn't get what amp he was trying to repair - not clear in the original post. It would have been if the above was copied here... thought he was trying to repair the Hafler.
 
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I

ilimzn

Member
Joined 2005
IFixAudio said:
So...
What I gather so far here is that the IRFP240 and IRFP9140 should do the trick???
The SEMELAB ALF08N20K / ALF08P20K will not work? They are advertised as audio fets and are even in TO3 cases.
Sorry for the trouble to the group, I am a great tech but do not do well trying to interpret and interrelate MOSFET specs to replace 25 year old devices with something modern.

Thanks again

Jim
Click to expand...

Jim, sorry for that, DJK is right, got you wrong on what amp you were trying to repair.
Yes, IRFP240/9140 will do fine. Just check the output power supplies, IRFP9140 is a 100V part, the schematic states +-44V, which is 88V end to end, cutting it a bit close to 100V if the mains is high. The schematic also shows a multivoltage transformer, unfortunately unclear exactly what voltages it has on my copy. If it only has a 110/120V for US and 220/240 for Europe, you might want to change it to 120 or 240 respectively. Power lost will be negligible but the MOSFETs will not be unduly stressed in high mains conditions.

Regarding replacing 20 year old MOSFETs with something modern, lateral MOSFETs are actually the first type of power MOSFET used in audio on a larger scale, so it would be replacing something 20 years old with 30 year old technology :)
 
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