Finally, after 7 weeks of waiting, I have the original Toshiba JFets from punkydawgs (3 weeks over the ocean and 4 weeks in the local customs and post).
Punkydawgs kindly included these caps in the shipment. These caps loosly fit a pair of jfets, only I am not sure what would be a reason to use these. Some sort of shielding? Could some wise men give an advise?
Now, I will be able to continue working on my AJ problems with excess distortion and noise. I did try to put BC556 instead of LSJ74 to see how it goes, and was able to set zero offset on the output and much lower hum/hiss. I even measured the THD (with BC556) at 1W on 8 ohm and got it about 0.10% (what agrees with the simulation). So, LSJ74 are very much a probable cause of the problems. Will try to change them now.
But these newly received 2SJ74 will finally go to the AJZen boards - was waiting so long to built it already 🙂 Hopefully, my original board of AJ will not fry them while testing - as I did not understand what could happen with my initial LSJ74 - they worked fine on my first measurement but developed bad distortion soon after...
Punkydawgs kindly included these caps in the shipment. These caps loosly fit a pair of jfets, only I am not sure what would be a reason to use these. Some sort of shielding? Could some wise men give an advise?
Now, I will be able to continue working on my AJ problems with excess distortion and noise. I did try to put BC556 instead of LSJ74 to see how it goes, and was able to set zero offset on the output and much lower hum/hiss. I even measured the THD (with BC556) at 1W on 8 ohm and got it about 0.10% (what agrees with the simulation). So, LSJ74 are very much a probable cause of the problems. Will try to change them now.
But these newly received 2SJ74 will finally go to the AJZen boards - was waiting so long to built it already 🙂 Hopefully, my original board of AJ will not fry them while testing - as I did not understand what could happen with my initial LSJ74 - they worked fine on my first measurement but developed bad distortion soon after...
Attachments
Last edited:
to avitkauskas
I used a 2-component-adhesive which is used by the computer-freaks to mount
CPU-coolers on thre chips.
arctic silver thermal adhesive....
Cheers
Dirk
p.s.: you also can bend the two JFets together with some shrink tube -
but not really necesssary
I used a 2-component-adhesive which is used by the computer-freaks to mount
CPU-coolers on thre chips.
arctic silver thermal adhesive....
Cheers
Dirk
p.s.: you also can bend the two JFets together with some shrink tube -
but not really necesssary
Hi, I checked the wiring diagram of the Aleph j and I saw that the resistors n. 28 and n. 29 are 4k7 Ohm for green or red LEDs, but making a calculation the resistance should be 1k5 Ohm on 24V input ..?
My question is if I want to use a standard blue led with 15 mA of current and 3.00 V of voltage, do I always have to use a 4k7 Ohm resistor or according to 1K Ohm calculations.?
Thanks for your patience : D
My question is if I want to use a standard blue led with 15 mA of current and 3.00 V of voltage, do I always have to use a 4k7 Ohm resistor or according to 1K Ohm calculations.?
Thanks for your patience : D
That would be very, very bright. Even with an old LED.
A good rule of thumb with modern super bright LEDs is 1K per volt of PSU will give a brightness that will not be extremely bright.
In these projects I’m just using 15k as standard.
A good rule of thumb with modern super bright LEDs is 1K per volt of PSU will give a brightness that will not be extremely bright.
In these projects I’m just using 15k as standard.
In my experience, I ended up using 100k with the modern blue LEDs that I want to extend to the front panel, otherwise they are too bright 🙂
@tricksters, thanks for the reference to the heatsink plaster - good to know these things exist. I was usually using some heatshrink to keep transistors together.
Concerning your question about PSU capacitors and resistors - these are snubbers and are optional. In some of my amps I used these places on the PSU to put LEDs on the wires extended to the front panel (LED in the capacitor place) 🙂
Concerning your question about PSU capacitors and resistors - these are snubbers and are optional. In some of my amps I used these places on the PSU to put LEDs on the wires extended to the front panel (LED in the capacitor place) 🙂
Thank you
1A6 to 1A7 is good for Iq
that across 0R27 is 430 to 460mV
are those 2W or 3W Sissies?
you have dissipation of those in rails ~ 0.8W, so better to use 3W
that across 0R27 is 430 to 460mV
are those 2W or 3W Sissies?
you have dissipation of those in rails ~ 0.8W, so better to use 3W