I have blown mosfet 2SK405 paired with 2SJ115.i cant find the originals and have been told to use 2SK1529 / 2SJ200.The units I can get are real Toshiba jobs.So come all you electronics wizards throw me a ******* bone here and do the cross check for me and advice 
I have the data sheets but dont really know what to look for
These are for a Marantz PM 94 AMP.How much will the newer fets affect my bias ??
Waiting for a wizard
Seafire
I have the data sheets but dont really know what to look for These are for a Marantz PM 94 AMP.How much will the newer fets affect my bias ??Waiting for a wizard
Seafirecompare
conductance Yfs (5S)
Ciss, Coss (900pF, 180pF)
Vgs off (0.8V to 2.8V)
Vdss (200V)
Id (12A)
Pd (150W)
package (To3p= To247)
Pin allocation (GDS D connected to thermal face)
2sk1530 data shown in parenthesis ().
The bias depends very much on the Vgs of each of the devices. This varies enormously for all FETs, whether jFETs, or Lfets, or Vfets.
Changing any FET virtually guarantees that you will have a different Vgs and this in turn guarantees that you will have to adjust the bias back to specification.
conductance Yfs (5S)
Ciss, Coss (900pF, 180pF)
Vgs off (0.8V to 2.8V)
Vdss (200V)
Id (12A)
Pd (150W)
package (To3p= To247)
Pin allocation (GDS D connected to thermal face)
2sk1530 data shown in parenthesis ().
The bias depends very much on the Vgs of each of the devices. This varies enormously for all FETs, whether jFETs, or Lfets, or Vfets.
Changing any FET virtually guarantees that you will have a different Vgs and this in turn guarantees that you will have to adjust the bias back to specification.
seafire,
you are a painstaking person, which I don`t dislike. Well, if you ask me, I`d say it`s a step backwards. For 2SK405, Crss is 60pF specified at Vds 10, while for 2SK1529 it is 90pF at Vds 30 (capacitances decrease with increasing voltages). Hitachi went in the opposite direction in the case of 2SK2220, impressing me greatly.
you are a painstaking person, which I don`t dislike. Well, if you ask me, I`d say it`s a step backwards. For 2SK405, Crss is 60pF specified at Vds 10, while for 2SK1529 it is 90pF at Vds 30 (capacitances decrease with increasing voltages). Hitachi went in the opposite direction in the case of 2SK2220, impressing me greatly.
Hi seafire,
To be honest with you, different fets of the same type will sound pretty similar and possibly the exact same. The feedback network will impress the sonic character of the amplifier over a simple output change. No matter whether you had the original transistors or a replacement in the same family, adjusting the bias is required as AndrewT posted earlier. You really only need to confirm the specifications of the new devices meet or exceed (in maximum ratings) the specs in your original parts.
Step 1, get the service manual. There is no excuse not to do this. You may need it in the future.
Step 2, compare these parts. I'll show the N-channel specs. for each.
2SK405- 160 VDC, 8 A, 100watts, 0.8~2.8 VDC cutoff and 2.0 S (Yfs)
2SK1529- 180 VDC, 10 A, 120 watts, 0.8~2.8 VDC cutoff and 4.0 S
The compliments are correct as you have listed. They should be close to these parts that they are complimentary to.
You can see that the new part is rated for higher voltage, current and range of pinch-off voltages. Therefore, you should be able to properly set your bias currents without any circuit changes and they are rated higher than the old parts. In other words, safe to use in your amplifier.
So, clean the heat sink up. Sand down high spots, like the screw hole edges, with about 320 wet / dry paper using a flat block. You can finish with 600 for a really smooth surface. Use new thermal compound and insulators. I generally like to use mica insulators.
Make sure all your resistors are okay. If a gate stopper resistor is open, you can lose your output transistors instantly. So measure everything no matter how everything looks.
-Chris
Edit: The devices AndrewT mentioned are higher rated parts than the replacements that were recommended to you. Either will be fine, use the ones that are the easiest for you to buy of these. Don't mix the compliments around unless you are really in a bind.
To be honest with you, different fets of the same type will sound pretty similar and possibly the exact same. The feedback network will impress the sonic character of the amplifier over a simple output change. No matter whether you had the original transistors or a replacement in the same family, adjusting the bias is required as AndrewT posted earlier. You really only need to confirm the specifications of the new devices meet or exceed (in maximum ratings) the specs in your original parts.
Step 1, get the service manual. There is no excuse not to do this. You may need it in the future.
Step 2, compare these parts. I'll show the N-channel specs. for each.
2SK405- 160 VDC, 8 A, 100watts, 0.8~2.8 VDC cutoff and 2.0 S (Yfs)
2SK1529- 180 VDC, 10 A, 120 watts, 0.8~2.8 VDC cutoff and 4.0 S
The compliments are correct as you have listed. They should be close to these parts that they are complimentary to.
You can see that the new part is rated for higher voltage, current and range of pinch-off voltages. Therefore, you should be able to properly set your bias currents without any circuit changes and they are rated higher than the old parts. In other words, safe to use in your amplifier.
So, clean the heat sink up. Sand down high spots, like the screw hole edges, with about 320 wet / dry paper using a flat block. You can finish with 600 for a really smooth surface. Use new thermal compound and insulators. I generally like to use mica insulators.
Make sure all your resistors are okay. If a gate stopper resistor is open, you can lose your output transistors instantly. So measure everything no matter how everything looks.
-Chris
Edit: The devices AndrewT mentioned are higher rated parts than the replacements that were recommended to you. Either will be fine, use the ones that are the easiest for you to buy of these. Don't mix the compliments around unless you are really in a bind.
megajocke said:
MCM Electronics has these or their near cousins -- but they are nearly as expensive as the Renesas lateral MOSFETs.
The Renesas are a little better behaved with respect to tempco, the Toshibas seem to squeek out a teeny lower THD% -- so pick 'em. See Troy Hueber's application note at National Semi.
(You can use the Renesas and adjust the bias with only a potentiometer, the Toshibas need some temperature compensation.)
seafire,
please don`t worry, these are indeed very nice devices for audio use, in practice, you probably won`t notice any significant difference. Higher transconductance enhances linearity, Vgsth has the same low level indicating maintained structure (thereby they are fundamentally equal), moreover improved power handling.
please don`t worry, these are indeed very nice devices for audio use, in practice, you probably won`t notice any significant difference. Higher transconductance enhances linearity, Vgsth has the same low level indicating maintained structure (thereby they are fundamentally equal), moreover improved power handling.
Hi,
the Lfet have similar Vgs, but the transconductance is ~1S.
This requires the drive voltage to be doubled (with respect to a 2S device) to get the same current out of the Lfet device.
Don't use Lfets to replace high transconductance Vfets unless you are prepared to redesign the amplifier to specifically suit Lfets.
the Lfet have similar Vgs, but the transconductance is ~1S.
This requires the drive voltage to be doubled (with respect to a 2S device) to get the same current out of the Lfet device.
Don't use Lfets to replace high transconductance Vfets unless you are prepared to redesign the amplifier to specifically suit Lfets.
Not you.Lumba Ogir said:
It's Jack and Foo that have twice said to try Lfets.
I was beginning to think that the 405/115 were not Vfets and that's why I asked what he needed for our clarification.
The higher transconductance (4S cf 2S) has already been addressed in the better linearity answer.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.