Hi GandRalf,
this Looks like the amplifier is oscillating. Congratulations, this seems to be the second confirmed case (out of 670 boards, that is). Please check the assembly guide for how to fix that, there is a description in there. Hope that helps!
(why say sorry for €15K Agilent scope pictures)
Believe me. -It took a whole lesson for me, by the lab. ing., to use it. 😀
@ hesener:
Do I have to be pleased?
Yes I know that remedy to solve, but was unsure about the signallevel.
I thought this could be external interference. Cause the boards were not shielded and powered by a simple supply at the same time.
I will try to test each board at its own.
-If I get a new chance to use the lab...🙄
Just looking through my bag of bits, and there's a bundle of J109 in there. I know it was said they were no good in the psu, but are they fine on the other side or does a better replacement for the j310 exist?
...So besides the PSU J109 -> J113 replacement, is there any other changes that is recommended to do?
I read somewhere about J107 replacement, is that something to look at or is it perfectly fine as it is?
I haven't started building, since i'm working on other projects - but i'm going to order components so i'll have them ready when i start...
I read somewhere about J107 replacement, is that something to look at or is it perfectly fine as it is?
I haven't started building, since i'm working on other projects - but i'm going to order components so i'll have them ready when i start...
sorry it was meant as a joke. If the noise is a few MHz, it's the Shunts; if it is 70MHZ and higher, it's the amplifier... At least I have seen no Variation from that pattern yet.....
let us know the outcome!
transistor swaps:
I've just matched my most recent batch and could do with some swaps.
I need...
327's in the range 430-450
337's in the range 410-430
Please let me know what you have and need i have lots of 327 in the 395-405 range
I've just matched my most recent batch and could do with some swaps.
I need...
327's in the range 430-450
337's in the range 410-430
Please let me know what you have and need i have lots of 327 in the 395-405 range
So was my reply.😉
Sorry for that. That`s the problem if we try to do ironic in a not native language.
Should have used a smilie then...🙄
(Back from holyday) The PSU JFets should be J113 and the Rgs for these is 1K (replace the 3.3K resitors)
On my PCBs they are between the transistor marked J310 and the 1uF capacitor, closed to the exit of the shunt.
I purchased a bunch of 2sk170 from Zhoufhang on ebay, I only need 6 of them so there are 3 sets of 6 up for grabs. First pm's get them
These transistors have driven me mad over the course of two builds. I've had awful matches, with little overlap between 327 and 337. Then yesterday i get 100 337 from farnell and more than 50% of them measure between 390 and 420 for Hfe.
So I now have the input stage matched with identical values across both channels, not 1% or 5% but the exact same values. Every other 327 and 337 on both channels is matched within 1%.
Crazy..
I must say I'm quite excited to power this up and measure it to see if it is any different to my 5% build.
So I now have the input stage matched with identical values across both channels, not 1% or 5% but the exact same values. Every other 327 and 337 on both channels is matched within 1%.
Crazy..
I must say I'm quite excited to power this up and measure it to see if it is any different to my 5% build.