F5X -- the EUVL Approach - The Build Thread

matching

Use this method to trace?
 

Attachments

  • JFET_matching.png
    JFET_matching.png
    81.8 KB · Views: 618

For all of the bias work it is necessary to short the + and – amplifier inputs to ground on the input board.

Do I need to connect the two input holes to the Gnd?

I measured the R18A, R19A, R24A and R25A and they are between 047.5mV to 050.5mV. Am I close?
 

Attachments

  • connection to gnd.jpg
    connection to gnd.jpg
    399.8 KB · Views: 606
Last edited:
Member
Joined 2009
Paid Member
>Do I need to connect the two input holes to the Gnd?

If you have the input relay in place they will already be grounded by resistors (if I remember right via 1KR resistors R101 and R103). Measure the resistance between gnd and the inputs to be sure.
 
>On the 'Degen Resistor Image' :
1) Is the regen resitors solder onto these pads?
2)Are the jumpers position for the Q11A, Q14A, Q10A and Q7A correct?
3) Is it okay if I didn't remove the tefron sleeve for the jumpers between Q6 and Q15?

Yes, yes and yes.

>On the 'Mute Connection Image':
4)Does the last hole on the Mute board extend all the way to the amp board or is just extended to the Input board only?
5) The holes right after R103 and R104, where do these goes to?

The wire does not go all the way to the amp board.
The two holes are the amp inputs and goes to the XLR sockets.

I'm a bit confused.

Regarding #1 - Degen resistors are also required at the locations pmchoong has shown? My understanding is they were only required at the (2) locations shown on Dave's build guide (first page of this thread).

Regarding #4 - I soldered this connection all the way down to the amp board, because it seems like there are no traces to this hole. I could be wrong though.
 
Looks like Dave is too busy with work and I have to jump in.

1) The pads shown are not for degen resistors. Greg is correct, only 2 locations required at the source pin of the 2SJ74s.
Those pads were placed there for the cascoded version.

4) The daughter board is to connect the input of the XLR, after the 1k/100k divider, to the main board.
So other than Gnd connection, there are 4 wires going down to the main board (to the gate pins of the JFETs to be precise).

I don't want to spoon feed, so you can trace all these by following the schematics.
That way you will have a deeper understanding of what you are soldering, which is my goal.
So, if in doubt, compare the tracks on the PCB to the wiring of the schematics.


Patrick
 
Member
Joined 2009
Paid Member
Hi Nic,

Are you done with the protection board yet?

Yes - but I cannot make them work as I want.
I'm in contact with ashaw and we are trying to solve the problems together.
I recommend keeping the assembly of these boards on hold for a bit. It is probably just my wrong, but anyway.
Note that the standard jumper configuration posted previously makes little sense for the F5X without regulated supplies.
 
Yes - but I cannot make them work as I want.
I'm in contact with ashaw and we are trying to solve the problems together.
I recommend keeping the assembly of these boards on hold for a bit. It is probably just my wrong, but anyway.
Note that the standard jumper configuration posted previously makes little sense for the F5X without regulated supplies.

I will probably wait until you sort out the control board issues with Ashaw before I start assembling mine. When you get the control board up and running as you want, do you mind posting photos before closing up your case? It would be helpful to see the board fully soldered and with the jumpers in place. :)
 
Member
Joined 2009
Paid Member
I will probably wait until you sort out the control board issues with Ashaw before I start assembling mine. When you get the control board up and running as you want, do you mind posting photos before closing up your case? It would be helpful to see the board fully soldered and with the jumpers in place. :)

That means I will have to expose my SMD soldering skills in public:eek: