Help with Big Muff Build

Started by Giglawyer, September 01, 2014, 04:09:55 PM

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Giglawyer

Aigh...please help.  I am not above begging...

Building a guitarpcb.com Muff'n build (Ram's Head Version).  I can't get it to work.   :icon_evil:  Any help would be appreciated.  Here are the relevant details:

Build guide:  http://www.guitarpcb.com/PDF%20Files/MUFFN_v2.pdf
Mods:  http://www.guitarpcb.com/PDF%20Files/MuffN%20-%20ABG.pdf

D1 - Cathode and Anode both 0v
D2 - Cathode and Anode both 0v
D3 - Cathode .63v, Anode 0v
D4 - Cathode 0v, Anode .63v
D5 - Cathode .71v, Anode .59v
D6 - Cathode .59v, Anode .71v
D7 - Cathode 9.25v, Anode 0v
D8 - Cathode 0v; Anode 9.25v; Cathode 0v (LED)
Q1 - E 9v; B 9v; C 0v
Q2 - E .4v; B 0v; C 0v
Q3 - E .08 v; B .71 v; C .71 v
Q4 - E 4.63v; B 1.63 v; C 1.03 v

I am using 2n5133's, but they are Motorolas that have higher gain (300-400 hFE).    I can't find any solder bridges. 
I did Mod 3, Mod 4 and Mod 5 in the advanced instructions.

Here are some pictures: 



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LucifersTrip

those voltages are so far out there that there's a good possibility of more than a single mistake, either in measuring or on the board.

The BMP is 4  linear stages, so you can easily work on one stage at a time. Start at #1.

Q1 - E 9v; B 9v; C 0v

This means that E & B are possibly connected/shorted and that C is grounded, but should be around 4.5V


always think outside the box

TGP39

Never built this before, but that schematic shows PNP transistors being used and 2N5133 is an NPN tranny according to my data sheet.

GibsonGM

Quote from: TGP39 on September 01, 2014, 08:18:02 PM
Never built this before, but that schematic shows PNP transistors being used and 2N5133 is an NPN tranny according to my data sheet.

...which should mean you'd be looking at near 9V on the C, with E and B appropriately lower...
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Giglawyer

The guitarpcb build is definitely NPN.  The transistors recommended are 2n5088, 2n5089, bc550 and 2n5133, all NPN.

I am carefully redoing every joint.  We'll go from there...LOL
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LucifersTrip

yes, I posted an original schematic, but guitarpcb (see link in 1st post by op) uses npn...

op:
if you have a breadboard, you can quickly lay stage 1 (c1 - c3) down for a comparison
always think outside the box

GibsonGM

I'd maybe start with checking where the power hits the board, see if you have + and - reversed?
  • SUPPORTER
MXR Dist +, TS9/808, Easyvibe, Big Muff Pi, Blues Breaker, Guv'nor.  MOSFace, MOS Boost,  BJT boosts - LPB-2, buffers, Phuncgnosis, FF, Orange Sunshine & others, Bazz Fuss, Tonemender, Little Gem, Orange Squeezer, Ruby Tuby, filters, octaves, trems...

Giglawyer

Quote from: LucifersTrip on September 02, 2014, 03:33:59 AM
yes, I posted an original schematic, but guitarpcb (see link in 1st post by op) uses npn...

op:
if you have a breadboard, you can quickly lay stage 1 (c1 - c3) down for a comparison

I will try that soon if need be. Thanks for the input.
Check out my builds - http://www.giglawyer.com

Giglawyer

Quote from: GibsonGM on September 02, 2014, 06:44:45 AM
I'd maybe start with checking where the power hits the board, see if you have + and - reversed?

I checked that earlier; that's one thing I did get right.  Thanks for the thought.
Check out my builds - http://www.giglawyer.com

LucifersTrip

#9
btw, here's a full set of voltages from ggg
http://www.generalguitargadgets.com/pdf/ggg_bmp_instruct.pdf

their C voltages are around 4, most likely because they use higher hfe transistors 300-500hfe+

my green russian original has higher C voltages, which are far more similar to what I get when I make the older models with transistors with gains of 150-200 like you're doing
http://www.luciferstrip.com/fuzz/green-russsian-guts.jpg
always think outside the box

Giglawyer

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