F5X -- the EUVL Approach

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H

heinz1

Member
Joined 2008
Now, I'm somewhat confused:

This offer of yours in the build thread (#585) dated 19th May 2013, Alexis, apparently never took place.

ashaw said:
Just touching base, I am currently in exam period, to make up for the delay, anyone who wants a corrected pcb, please email me and I will send you the number you need free of charge, but get in quick ill order them on Wednesday, if I run out you miss out.

Regards
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I've sent you a PM then, but I don't recall that I ever received a corrected PCB. I have just contacted WK by PM for a corrected PCB.

But generally, shouldn't this discussion be continued in the build thread?

http://www.diyaudio.com/forums/pass-labs/208880-f5x-euvl-approach-build-thread.html
 
A

ashaw

Member
Joined 2006
I have been dealing with serious medical issues, I am only now starting to get on top of them. I have not been doing much of anything since that time. I would rather not have to talk about them, and am sorry about the delay. If euvl arranges for PCBs to be made for those who want them I will pay the invoice, I cannot do much more than that at the moment.
 
H

heinz1

Member
Joined 2008
EUVL said:
We only have 6 left, I was told.

If there are more demand then we'll have to make new and send all in one go to save work for WK.


Patrick
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Thank you very much, Patrick.

I have set up a list showing interest here:

http://www.diyaudio.com/forums/grou...up-buys-related-euvls-f5x-34.html#post3665184

Alexis, I am very sorry to learn of yout medical problems and I hope you feel better now. It us very kind of you that you want to pay for the boards, but I shall pay for it by myself.
 
Horio

Horio

Member
Joined 2010
EUVL said:
I cannot understand why it is too much work to make a small PCB repair.
Nic did it, Greg did it, without an issues.


Patrick
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The repair isn't too hard to implement, but it does take some care. You just need a sharp knife (like an xacto), a magnifying glass, a very small gauge wire and some patience. Go slow when carefully scraping off the epoxy over the trace. Don't use a dull big knife for this process.

To make the new connection, I used a very thin gauge lead from a low wattage resistor. I carefully bent the lead to make sure that it laid flat on the board and did not create any accidental bridges. I then tinned the exposed traces. Lastly, I laid the wire on top of the exposed traces, flooded it with liquid flux and heated the connection with my iron (which had a little bit of solder on the tip as well). Seem to do the trick. :)

Just be careful not to push on the wire too hard after soldering or you might pull the trace out of the board. The big thing is to just take your time, and go slow. I'd do the fix before you populate any of the board. That way if something does go wrong, you can try to order a new board with the fix implemented.

Give it a shot. Knowing how to do this type of repair is a good skill to have in your back pocket. :D
 
T

toxic ingestion

Member
Joined 2012
EUVL said:
I have been asked why there is a need to match for transconductance, when we already matched tightly for Idss.

The attached graph are two 2SJ74BLs with identical Idss, actually measured with a curve tracer.
As you can see, real devices do not obey theoretical equations.

To match for transcoductance for F5 without a curve tracer, the following procedures are sufficient :

2SK170BL -- measure Id with 0R, 11R, 22R degeneration
2SJ74BL -- measure Id with 5.1R, 16R, 27R degeneration

Devices (NNPP) with identical values for all 3 columns are best matched for the F5X.


Patrick

PS These procedures will be described in more detail by the test team eventually

.
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Hi,

I know I read some time ago somewhere on this thread or another one by your team with transconductance curves for matched 2JS74 and 2SK170 that illustrated how about 5 ohms of resistance on one of these devices caused the very similar curves to become almost identical. Searches within diyaudio.com and using google have not led me back to that page that I know exists. Might someone have the url for that particular post? Thanks.
 
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