This is in a Nad 218THX amp.
Any recommendations for replacing 2sd1975/ 2SB1317?
(Need to replace all)
Been looking and looks like 1943 / 5200 from ON/fairchaild could be ok. Although freq is at 30mhz instead of 20mhz. ONs are hfe 80, also a version with hfe 50. Not sure what to choose. What difference does it make here. Can’t find exactly what hfe the Panasonics have.
Can i keep everything else the same? Right now res are 0.22R. Bias is recommended to be at 8-10mv
Same with new ones?
Would be nice with just a swap.
Pinout should be same too and to-264 also.
Thx for help
Any recommendations for replacing 2sd1975/ 2SB1317?
(Need to replace all)
Been looking and looks like 1943 / 5200 from ON/fairchaild could be ok. Although freq is at 30mhz instead of 20mhz. ONs are hfe 80, also a version with hfe 50. Not sure what to choose. What difference does it make here. Can’t find exactly what hfe the Panasonics have.
Can i keep everything else the same? Right now res are 0.22R. Bias is recommended to be at 8-10mv
Same with new ones?
Would be nice with just a swap.
Pinout should be same too and to-264 also.
Thx for help
Nad says in the manual that bias should be set between 8mv (+/-2mv) and that what i can see the Panasonics are To-264 package mounted to chassie on big heatsinks (whole chassie basically can cool them down)
With the bias i meant can i set bias to the same with the new ones (for example if these ON will work)
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ON Semiconductor MJL21193 and MJL21194 is a good replacement.
https://www.onsemi.com/pub/Collateral/MJL21193-D.PDF
Many high power output amp and THX power amp using these high power output transistors.
-High DC Current Gain
-Excellent Gain Linearity
https://www.onsemi.com/pub/Collateral/MJL21193-D.PDF
Many high power output amp and THX power amp using these high power output transistors.
-High DC Current Gain
-Excellent Gain Linearity
I didn't do that before, I read many high end power amp review articles and many of the high end amp using these power transistors and their review result is positive.
I know many NAD models built with cheap cap, so as the power supply cap and normal component as well.
Since you want to upgrade your amp, I think you would upgrade with better components.
This Parasound HCA-1500A using MJL21193 and MJL21194 and they are good.
Parasound HCA-1500A repair and possible upgrades
I know many NAD models built with cheap cap, so as the power supply cap and normal component as well.
Since you want to upgrade your amp, I think you would upgrade with better components.
This Parasound HCA-1500A using MJL21193 and MJL21194 and they are good.
Parasound HCA-1500A repair and possible upgrades
Yes. Both teams are ok for the job. 5200/1943 I consider better. Beta is up to 100, so less demand from previous stages. Check Ccb recommended.
Yes. Initial warming up is with a 10mA setting, then increase to 36mA per branch. Warming up is at 0.75W, operation at 2.7W per bjt.
Depending on the size of the grill, I'd prefer more class A settings.
Indeed. Pinout is the same.
Other DIY members are welcome to commend. I do not know everything.
With 10mA or 8 i mean at the testpoints pointed out in the manual.
Isn’t then 10x8bjt=80mv per channel?
The 4 pairs of bjt are on heatsinks and think only c3788 and 1493 is mounted on the board.
If you mean 36mv isnt that quite hefty
I'm talking mA, not mV.
Alignment says 2-2.5mV (10mA) initial warming up.
Then readjust to final setting 8+/-2mV (~36mA).
10??? No, there are 6 junctions in series. This applies to the total biasvoltage set with VR301-302.
That's ok for me, though I expect Q321-322 (& poss Q323-324 also) on the grill. Temp stabilisation!
...Then readjust to final setting 8+/-2mV (~36mA):
[8 - 10 - 12 ] mV / 0.22Ω => [ 36 - 45 - 55 ] mA
Given Vps = +/-72<>76Vdc, say +/-75Vdc, Pdiss:
Pd = 75 * 45m = 3.4W
That's for the two channel amp 54W central heating.
Say 100mA idle dc current per channel, that's 80mW classA drive.
Approx 0.3% classA efficiency, so definitely a class AB amplifier.
Attachments
10mv x 8 bjts (4pnp/4npn) i meant.
6 junctions? There is 4 pair of bjts each channel.
When you say central heating 54w do you mean the 72/76v supply? The 82v unreg is not important here?
Nads designer of this amp said this was running in class A up to 10w? So not any truth to that?
What would you do to let this amp run wither higher bias/ class A? Is it even possible?
I’m thinking recap, retran(?) this Thing so it hold for me atleast 10yrs and it will be my main amp.
So basically it seems like its quite easy to replace all trannies with 5200/1943 (basically plug and play)
6 junctions? There is 4 pair of bjts each channel.
When you say central heating 54w do you mean the 72/76v supply? The 82v unreg is not important here?
Nads designer of this amp said this was running in class A up to 10w? So not any truth to that?
What would you do to let this amp run wither higher bias/ class A? Is it even possible?
I’m thinking recap, retran(?) this Thing so it hold for me atleast 10yrs and it will be my main amp.
So basically it seems like its quite easy to replace all trannies with 5200/1943 (basically plug and play)
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