MarkM DOD 250/Mosfet Boost layout build report

[tungngruv]

I perfed up both the 77' od 250 and AMZ Mosfet Boost using MarkM's layouts. Worked great, fired up first time. The 250 sounds really good, retains the signature sound through a tube amp and the Mosfet boost is really a clean boost. I boxed them both up in the same box, 250 closest to the guitar, booster afterwards. With this set up, I can get my Marshall sounding really great with the 250, then punch up the solo's with the Mosfet boost without getting mushy or overly saturated. Here are a couple things I found while building them:

OD 250:
The gain pot works backwards, so reverse the connections to fix that.
The layout uses two 1M resistors and no 470K. After looking at several schems, I'm pretty sure the 1M coming off pin 3 should be a 470K.

AMZ Mosfet Boost:
I didn't have the 100K trim so I was able to get the 4.5v right by using a 47K in series with a 25K trim. Worked great.
The symbol for the mosfet was "flipped around" (I used a 2n7000), so follow the schem and know your pinout to make sure the DGS are in the right place.

Great job Mark, really fun using your layouts.
BTW Mark, off topic but here's a clip of my SkyRipper that I made with you in mind (sad, sad attempt at country)

http://home.grics.net/tungngruv/22FenderOverdriveReverbAdded.mp3

Thanks again Mark for the layout and JHS for making the 77 information available!

[petemoore]

  That has a nice Country Crunch to it !!

[John Lyons]

Nice clip of the country riff Tung, now we just need a clip of the OD250 and Mosfet boost!
Mark is keeping us busy with all these layouts for sure. Grrrrr...

[Barcode80]

that sounds interesting, good combo of effects in one box. did you put anything between the circuits or just straight from the out of one to the in of the other?

[tungngruv]

did you put anything between the circuits or just straight from the out of one to the in of the other?

Just both in one box, two stompswitches connected, one switch output to the other switch input. I think GeneralGuitarGadgets has a diagram by Ricky V. Make sure the boost comes last, or else it will affect the distorted tone.

I'll try to get a 250/Boost clip up this week, shoudn't be too hard!!

[Barcode80]

i'm a little confused about something on markm's layout of the mosfet boost. is R2 supposed to be there, or is the trimpot supposed to replace it? or are you supposed to use the trimpot to find the proper resistance then put in a resistor of that value? i guess either would work, i just wonder are they both supposed to be there?

[markm]

i'm a little confused about something on markm's layout of the mosfet boost. is R2 supposed to be there, or is the trimpot supposed to replace it? or are you supposed to use the trimpot to find the proper resistance then put in a resistor of that value? i guess either would work, i just wonder are they both supposed to be there?

I realize now that the notes on my Mosfet Boost layout are about as clear as mud 
Okay, I put R2 in as an option for the more ambitious builder so the solder pads for a resistor would be in the PNP and one could sub the trim pot for a resistor if desired.
I sometimes prefer to set the circuit up with a trimmer, find the ideal bias point, measure the trimmer and then sub in a resistor to free-up the trim pot for another build.....other circuits I just leave the trimmer in.
I just added it as an option so the builder could use a resistor or a trim pot.....that's all.

tungngruv.....
That is some mean Country guit-pickin' right there, sounds GREAT and made me smile when I heard it!
Thanks for making my day 
I checked this layout for the pinouts on the tranny and they are correct according to the BS170's I have which are Fairchild.
The pinout is SGD for them.
Don't know why you had to flip yours but, I'm glad it worked out for you.
Keep up with that country playing!!

[tungngruv]

I used a 2n7000 that had DGS so it worked, just flipped around. Don't be too hard on yourself, your layouts are great!!! Everyone should use a layout along with the schem, right? As far as the country playing, not for a while , I set a "winter" goal for myself to learn as many of Michael Schenkers solo's on the live UFO album "Strangers in the Night" CD as I can and I'm more than halfway there. I'm really digging the late 70's European guys lately......... Michaels definitely one of the best!! Thanks again for taking the time to draw up the layouts Mark.