Hi eveyone
First of all thanks to all posters for their kind help.
I post my experience here in hope it could help others in the future.
Initialy I went J175 but sadly that didn't work as expected. I am used to handle transistors and even far more complicated/sensitive SMD parts, did the bias with them 2 decades ago and soldered very recently some in the B1 Korg and the H2 kits. All without frying a single part or any trouble, never ever. All my parts are presumably genuine and come from Mouser.
Well, I bought 4 J175 for testing and fried my first part in decades trying to test one on my bench, 2 didn't respond as expected and the last one seemed to be OK. That with 2 different mutimeters and 2 different ways to measure them. All on the bench, no real trouble, couple of bucks gone.
I switched to Fred's advice, J112, ordered 12 of them (becoming suspicious), applied the same process on the same bench... and all worked fine without any problem and responded as expected (bare maybe a current that could climb to 20mA). All could be adjusted very easily with 270R or 750R depending on the unit as there were variations as Fred described.
Bottom line, I don't know if I was unlucky with a batch, or if J175 is so sensitive that it desintegrates just breathing at it, but J112 is far easier to work with and works fine for me. Handling is not too sensitive which allows also to solder / mount it. Special mention to Fred.
I hope this saves other times and hassle
Claude
First of all thanks to all posters for their kind help.
I post my experience here in hope it could help others in the future.
Initialy I went J175 but sadly that didn't work as expected. I am used to handle transistors and even far more complicated/sensitive SMD parts, did the bias with them 2 decades ago and soldered very recently some in the B1 Korg and the H2 kits. All without frying a single part or any trouble, never ever. All my parts are presumably genuine and come from Mouser.
Well, I bought 4 J175 for testing and fried my first part in decades trying to test one on my bench, 2 didn't respond as expected and the last one seemed to be OK. That with 2 different mutimeters and 2 different ways to measure them. All on the bench, no real trouble, couple of bucks gone.
I switched to Fred's advice, J112, ordered 12 of them (becoming suspicious), applied the same process on the same bench... and all worked fine without any problem and responded as expected (bare maybe a current that could climb to 20mA). All could be adjusted very easily with 270R or 750R depending on the unit as there were variations as Fred described.
Bottom line, I don't know if I was unlucky with a batch, or if J175 is so sensitive that it desintegrates just breathing at it, but J112 is far easier to work with and works fine for me. Handling is not too sensitive which allows also to solder / mount it. Special mention to Fred.
I hope this saves other times and hassle
Claude
All MOSFETs are static sensitive and just touching the gate can easily blow them up, although the explosion area is measured in nanometres its enough to ruin it. Anti-static wristband will make a big difference to this scenario, but still never handle the gate directly.
My recommendation is that gate and source should be in conducive black foam until mounted in the circuit, and never wear nylon.
Conducive foam doesn't stop you testing a device as its very high resistance.
I suggest installing them source pin first, not gate. It makes sense to populate the passives/diodes/BJTs in a PCB before MOSFETs as this brings all the traces to the same potential (from the perspective of static charge).
The drier the air the more likely static will be a problem, but just mains-pickup is high enough in voltage to trash MOSFETs, so wrist-band...
My recommendation is that gate and source should be in conducive black foam until mounted in the circuit, and never wear nylon.
Conducive foam doesn't stop you testing a device as its very high resistance.
I suggest installing them source pin first, not gate. It makes sense to populate the passives/diodes/BJTs in a PCB before MOSFETs as this brings all the traces to the same potential (from the perspective of static charge).
The drier the air the more likely static will be a problem, but just mains-pickup is high enough in voltage to trash MOSFETs, so wrist-band...
I suggest the LM334 3-terminal TO-92 case current source. Programmable up to 10mA using only one resistor.
Mouser part number: 926-LM334Z/NOPB
Walt Jung measured the audio band A.C. impedance of this device @ 2mA, in his current source article originally published in Audioxpress magazine in 2007. Shown in figures 7A and 7B therein.
https://audioxpress.com/assets/upload/files/Sources_101_P1.pdf
Mouser part number: 926-LM334Z/NOPB
Walt Jung measured the audio band A.C. impedance of this device @ 2mA, in his current source article originally published in Audioxpress magazine in 2007. Shown in figures 7A and 7B therein.
https://audioxpress.com/assets/upload/files/Sources_101_P1.pdf
Yep,thanks, all good recommendations... as said, never had a problem in a few decades and handled quite a few recently... retested the 12 J112 today and all worked perfectly and same as a few days ago... I need to handle these parts to mount them best I can around a DP8 sockets, so prefer less delicate parts...
Thanks to everyone again
Claude
Thanks to everyone again
Claude