help debug my first stripboard build! - axis fuzz (fixed)

corbs · June 23, 2005, 02:21:41 PM

eugh i have no idea whats wrong...

Q1 NPN (2N3904)
E 0.27 B -0.2 C 0.23
Q2 PNP (2N3906)
E 5.59 B 5.61 C -0.02

V across the battery was ~10V :?

i'd really like to get this going as it's the first thing i've actually moved from my breadboard (it was on there a long time â€" but did once work) onto something more permanent.

MartyMart · June 23, 2005, 03:13:14 PM

Corbs,
First off, Q1 should be PNP 3906 and Q2 should be NPN 3904 ...!
Do you have them swopped, as that will produce - zero sound

Marty.

corbs · June 23, 2005, 03:51:49 PM

Quote from: MartyMartCorbs,
First off, Q1 should be PNP 3906 and Q2 should be NPN 3904 ...!
Do you have them swopped, as that will produce - zero sound

Marty.

ah no they are placed as per the scematic

i couldn't see any Q labols so i made my own

- is there a numbering system?

MartyMart · June 23, 2005, 03:59:47 PM

No problem Corbs, I was just "checking" :wink:
Yes there is normally a designated "transistor" numbering system, which
runs from "input" through to "output" of the circuit.
If there are three transistors, then it's Q1 - Q2 - Q3
This is NOT always right to left on a schematic, you have to follow the
"flow" of the circuit path sometimes .
The "sticky" at the top that says "what to do when it doesn't work" is very
valuable and you should read and follow that set of guidelines.
It will help us to help you and you'll understand a lot more about your builds after "de-bugging" a few

Regards,
Marty.

corbs · June 24, 2005, 05:07:36 PM

one correcly connect 100k resistor and a few resolderd joints later i have some sound - kinda like crazy interference fuzz thats very slightly effect by the guitar...

i'm getting closer

corbs · June 27, 2005, 11:06:31 AM

ok well still no luck - i get a rough interference fuzz sound only when i turn the volume up full (turning it all the way off still produces some clean sound) gain needs to be turned up a bit too. upon turning the transistors around i get correct base - emitter voltages (although low) but i get no effect.

when i disconnect the input cap (it's on a rotor switch) i get some of the clean signal though, even if i disconnect the transistors (although quiet) which i guess is coming though the -ve path. this would also explain the volume pot problem. is this normal?

i've checked the routing over + over and i'm sure it's fine. the only thing i can think of now is a dodgy component. btw i've tested that 2M2 in circuit - the multimeter takes a while to get there but it is 2M2 Ohms.

MartyMart · June 27, 2005, 11:48:35 AM

Sounds like a "mis-wire" some where, make sure that the three transistor
connections, for each tranny are not "bridged" over with the lead/solder
Even a very small "hair sized" connection can ruin a good circuit !!

Best of luck, and just think how much you are learning by doing some
"de-bugging"

( bet you "really" wanted to hear that eh ?? )

Cheers,
Marty.

corbs · June 27, 2005, 04:47:21 PM

Quote from: MartyMartjust think how much you are learning by doing some
"de-bugging"

if only

think i'll put this away for now... don't want to go insane yet

corbs · June 30, 2005, 04:40:28 PM

it's me again

, this time with a vero layout

it's a lot to ask (it's quite a messy layout) but if someone with fresh eyes could look this over to see it it matches the schematic i would be much obliged.

DiyFreaque · June 30, 2005, 05:07:27 PM

It looks to me like the layout has the collector of Q1 connected to nothing, and the bases of Q1 and Q2 tied together. The collector of Q1 should connect to the base of Q2 with no connection between the bases (according to the schematic).

Cheerio,
Scott

corbs · June 30, 2005, 05:43:13 PM

thanks for looking! and your quite right - alas this was an error in the copying the circuit it's actually right on board.

the image has been corrected

corbs · July 03, 2005, 07:45:05 AM

just a quick bump - and a note to say i've updated the the vero layout with all the voltages i'm getting

it appears the NPN tansistor is getting incorrect base / emitter voltages. can anyone guess why?

cheers

petemoore · July 03, 2005, 07:58:12 AM

Sure...the resistances aren't setting up proper bias conditions.
There's a bridge that shouldn't be.
Something that should be connected, isn't.
I'd do thorough testing of resistances around that transistor...looking for higher than stated resistances than shown on schematic...and...lower than shown resistances can be seen, but are possible 'misnomers' because of alternate path through the circuit [in circuit resistors CAN be tested, but if low value is found...either calculate everything between the test points, or pull one end out or the circuit and repeat R value test.].
I generally don't actually ever have to pull a resistor, but checking like this has shown me errors.

petemoore · July 03, 2005, 10:36:30 AM

A 'different approach is to look at it from the *nodes, looking at and comparing the schematic to the board, counting the # of connections at each node.

corbs · July 05, 2005, 05:09:23 PM

guess who didn't connect the guitar input sleave to ground... no go on guess...

:oops:

wow, won't be doing that again.

petemoore · July 05, 2005, 05:54:41 PM

Nobody...I 'almost' forgot that for a second or two... :oops:

MartyMart · July 06, 2005, 04:27:49 AM

Quote from: corbsguess who didn't connect the guitar input sleave to ground... no go on guess...

:oops:

wow, won't be doing that again.

AHA !!
Dont worry we've ALL been there once or twice......
The best one is when you wonder why the hell your new "Overdrive"
clone of a clone of a TS/ShredBlaster clone..... doesn't work ....?

Then you see the "empty" 8 pin socket !!!! - NO opamp inside DUH !!

:shock:

Marty.

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help debug my first stripboard build! - axis fuzz (fixed)