ROG Matchbox Q source...

[phazerz]

Hi everybody
I've just finished the matchbox (stock part and value from torchy vero layout) this morning and it sound ok but I think I have a problem because I barely have some gain, just a good crunch but only at the very end of the vol/gain pot... with gain at 50% I have to crank master at 100% to reach unity.
Here is the pin voltage :
ROG Q1 9.1v (reminder) :
D : 4.8
G : 2.4
S : .300
mine (9.55v) :
D : 4.86
G : 2.41
S : 0.36

ROG Q2 :
D : 4.8
S : 1.0
G : .500
mine :
D : 4.85
S : 0.49 (?)
G : 0.07 (?)

ROG Q3
D : 4.8
S : 20mv
G : 0
mine :
D : 4.86
S : 0.03
G : 0.07

Maybe my J201s (Fairlight) are weak ?
All my 1k2 resistors are 1k17..

Any idea ?
Thanks for help !

[phazerz]

Well after one hour of playing the "clean-almost-crunch" sound of the matchbox I must say it's a great clean sound box !
http://www.runoffgroove.com/matchbox.html

If someone could try to explain me why i don't have a real overdrive it would be so nice !
Maybe it's a "normal" behaviour of the amp ? (only crunch at the very end of the gain pot ?) But where is the vox sound then ?
-Pots are verified
-wiring and layout too
-No other problems...

[Torchy]

Change the 4k7 resistor on Q2 source to get it to 1v ?

[phazerz]

Maybe should i raise the 1k2 only cos' i had to raise the 4k7 to 18k (!) to get only 0.75 Volts at source but my trimmer can't lower the drain under 5,7 volts now...
Something is wrong with my built ?

[Torchy]

I would try a different few fets at q2.

[MartyMart]

Check all your Q2/Q3 connections, could be a "miniscule" copper hair or solder bridge
( I've had 'em !! )
Run blade/jewellers screwdriver between all the traces etc

Sometimes these Jfet sims are a PITA, it's not an "exact" science, two builds can be
wildly different.
I would try several Jfet's also for fine tuning/optimal sound

MM.

[phazerz]

Thanks for your help Torchy & Marty, I'm very honored 
One thing i've omitted to say is that this amp sim is inside a big box with 2 other sim, 3 effects and a tonemender->sss->condor.
The supreaux sounds amazing with this chain and the matchbox like it is now is pretty good for clean sound (maybe need more bass).
I've read a R.G. post on grounding and at times i had some problems with the supreaux (noises) and i've learned everything you've said Marty : solder bridge and cat's hairs are in my Ray X now...
So i've star-grounded it : every ground points goes to a special veroboard and maybe this layout doesn't support this way : master vol and gain lug 1 goes to this point, could this be the problem ?
I've changed the value of the cut control for a 50K/47nF too.
But maybe my J201s are not so good (one batch with tape paper so they are pretty all the same...)
Thanks very much, i'll tell you more when it will be corrected !
Best'
--
(Well sorry, my english ? I'm just French ;-))

[MartyMart]

Check your grounding with your "multi" build, I have a similar setup in a rack unit,
Matchless, Supro,Bassman and cab sim.
I ran ground/power from board to board and have a "bolted" to the chaassis ground.
I/O Jacks are board connected too.

J'espère que vous l'obtenez fonctionnant très bientôt.

La correction peut être une vraie douleur dans le clochard !!!.

MM.

[phazerz]

What do you mean by "bolted" to the chassis ground ? Did you join all the ground wire with a BIG bolt to the chassis ?
My ground wiring is :
-In jack connected to the enclosure (aluminum)
-Out jack insulated
-Battery and DC power goes to the "special star vero" (no battery switch off with the stereo jack)
-In ground, Out ground, boards ground, pots ground, Led- goes to this card...
Is it correct ?
Thanks i go back to the box with my magnifying glass...

[phazerz]

Found it !...
One track cut is missing between Q2&Q3 gates... My fault, it doesn't appear on torchy layout but it is so bovious technically (maybe it is hidden behind R3)... And in my mind that's a good thing Torchy ! We are forced to read the schematic carefully and compare with the layout so we know what we're doing !
And now... i really have to join Marty post : "Matchbox sound superb!" I'm really impressed and the 6 pos switch is so usefull because the box sounds so great clean AND overdriven... you just have the choice depending on you're guitar...
Really, really beautifull... now i'm sure about it : i sell my tonelab !
Thanks so much guys,
Best'
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