Landtone Fuzz Face clone - Transistor issues

[willienillie]

For a positive-ground PNP fuzz face, the positive lead of the input cap should go towards the input jack tip.  Sounds like you did it right.  If the PCB is silk screened incorrectly, I wonder what other errors the kit maker may have made.

The "ring" of the stereo input jack gets shorted to ground by the mono input plug, not really a factor with respect to the input cap.

[guyshermannz]

The "ring" of the stereo input jack gets shorted to ground by the mono input plug, not really a factor with respect to the input cap.

I think I meant sleeve, which in this circuit is technically connected to +9V.

[guyshermannz]

please post photos of this thing you gave built, nice and clear so we can see "things" - solder side as well [some here like looking at those, but not me]. we also want to see any off-board connections.

The backside of the PCB


The front-side of the PCB


Side-shot of my janky Transistor socket. Pretty much an inline jumper socket on some veroboard, with wires coming off of it. The connections on it are legit. Have some proper sockets on their way, didn't want to heat the transistors.


Backside of the little breakout I did to add a bias pot (have a range of trimmers coming, but this will do for now. Comes onto the board, and then out to one side of the pot, back out the wiper, onto the board, through a 1k resistor, and then back off the board into the circuit.


Shot of the pots and my little breakout board for the LED in the case.

[guyshermannz]

For a positive-ground PNP fuzz face, the positive lead of the input cap should go towards the input jack tip.  Sounds like you did it right.  If the PCB is silk screened incorrectly, I wonder what other errors the kit maker may have made.

Apart from the transistor and the two ECs, the rest of the parts are non-polar, and the circuit corresponds to the circuit diagram posted earlier in the thread (I have traced and re-traced). The transistors are connected correctly, so unless the cap across the fuzz pot is the wrong way round, then it should all be fine.

I think my next step will be to breadboard the same circuit (fortunately I whipped up a janky transistor socket, as they're the only parts I don't have spares of), and see if I can get that going. Worst case scenario I can re-make it on veroboard.

Cheers,

Guy.

[duck_arse]

I have some stupid questions. is that mid-air 50k pot got solder in the lug rivets? we don't allow solder wires to the rivets, no matter how enticing they appear - it causes too many problems. have you wired the bypass switch correctly [all white wires doesn't help]? have you metered input to output for continuity when toggling the footswitch? and to that point - do the measured voltages change when you work the footswitch?

[guyshermannz]

is that mid-air 50k pot got solder in the lug rivets?

Yeah, it is a big janky, but also temporary, I did measure that it was working by measuring the resistance across the whole breakout assembly before soldering it to the board.

have you wired the bypass switch correctly [all white wires doesn't help]?

Yes, I have traced it point-to-point through the circuit, and also it works fine when "off" (ie the true-bypass is definitely wired up correctly).

have you metered input to output for continuity when toggling the footswitch?

I get continuity when bypassed, not when active. However, when I pass a very loud signal through it from my audio interface I do get sound out the other end, and I have traced point-to-point with a software signal analyzer (through my audio interface) to see that the signal is making its way through the circuit as expected.

do the measured voltages change when you work the footswitch?

I have not checked this. Will have a crack this evening and respond then.

[duck_arse]

the bypass is only half tested yet. meter from the in jack tip to the input cap on the board as you work the bypass, to see if sig reaches the input. then do the same for the out jack tip and the out cap or vol pot, whatever your circuit shows.

[guyshermannz]

the bypass is only half tested yet. meter from the in jack tip to the input cap on the board as you work the bypass, to see if sig reaches the input. then do the same for the out jack tip and the out cap or vol pot, whatever your circuit shows.

I do indeed have connectivity between input and input cap, and between the volume pot and the output.

[guyshermannz]

do the measured voltages change when you work the footswitch?

I have not checked this. Will have a crack this evening and respond then.

With something plugged in, they do change when I work the footswitch. In bypass they are fine, and then in active they go all messed up. This makes sense, as the bypass is disconnecting the input/output from the board. With no input plugged in there is no difference in the voltages when working the switch.

One thing I am a bit confused about, after doing the continuity checking, I seem to have continuity between the points labeled "COM" and "V" on the following image; regardless of which position the switch is in, or whether something is plugged into the input:

[guyshermannz]

So I breadboarded the circuit and it worked fine. So I then started comparing the pen to my breadboard version. I found that a bunch of points were connected to -9, when they should have been connected to 0. So, I cut a trace to separate them, but somehow I still have continually bets the eon -9 rail, and the part that should be 0v.





The blue circles correspond.

Anyway. I think I'm just going to veroboard it and be done with it.

Thank for all your help, I've certainly learned a lot about troubleshooting from your responses.

[duck_arse]

With something plugged in, they do change when I work the footswitch. In bypass they are fine, and then in active they go all messed up. This makes sense, as the bypass is disconnecting the input/output from the board. With no input plugged in there is no difference in the voltages when working the switch.

no, not making sense, pointing to a fault. the DC around the circuit should not change, for any reason. you should really draw your bypass switch as you have it wired, and see where your in and out caps are isolating the board/volts from the switch/jacks. your continuity checks have eliminated a reversed wired jack from the equation, so we are looking for something else.

[guyshermannz]

you should really draw your bypass switch as you have it wired, and see where your in and out caps are isolating the board/volts from the switch/jacks. your continuity checks have eliminated a reversed wired jack from the equation, so we are looking for something else.

Like this?




As mentioned above I found some more problems with the board, and I've updated the schematic to look more like the board. I attempted to modify the board so that most of those Vcc are actually "Ground" (which is really +9 in this case) - naturally the one by the battery would stay as Vcc.

[iainpunk]

did you try to drive a literal bare speaker directly with this circuit??


please tell us that that is a small amplifier and not a lone speaker.

cheers, Iain

[duck_arse]

nope. Vcc is called that because it connects/feeds the Collector/s. you now show Vcc as collector supply and emitter supply, resulting in 0 Volts across the device. name ground. connect the emitter ends to ground. connect all the commons to ground. connect all the earths to ground. THEN connect your supply, in this case, PNP transistors, you want 'positive ground'. so connect the battery plus/red to the ground/common/0V line, and the battery minus/-/black to Vcc, at the top. job done, easy.

you have it partly drawn correct, except you have named Vcc all along those bottom point, which should show the ground symbol. your switch as drawn should work correctly. we have to be sure as drawn is as built - there lies the rub.


I'm pretty sure this board/supplier/kit/build has come up a few times in the past. I though somone - either Pink Jimi or Cozybuilder - took the whole thing apart and traced and corrected a circuit diagram and parts placements to fix/suit - and posted a thread on it. but I haven't searched for it.

[iainpunk]

nope. Vcc is called that because it connects/feeds the Collector/s. you now show Vcc as collector supply and emitter supply, resulting in 0 Volts across the device.

i didn't even see that, lol 

cheers, Iain

[duck_arse]

no probs, boss.


someone really ought to tie all these threads together. again. here see, it's been done before, a few times ....

https://www.diystompboxes.com/smfforum/index.php?topic=120351.0
https://www.diystompboxes.com/smfforum/index.php?topic=119292.0
https://www.diystompboxes.com/smfforum/index.php?topic=118303.0

[guyshermannz]

did you try to drive a literal bare speaker directly with this circuit??


please tell us that that is a small amplifier and not a lone speaker.

cheers, Iain

No, I just didn't have a symbol for a jack, so I figured a speaker was the next best thing to indicate "signal goes out here". Looks like it was taken too literally 

[guyshermannz]

nope. Vcc is called that because it connects/feeds the Collector/s. you now show Vcc as collector supply and emitter supply, resulting in 0 Volts across the device. name ground. connect the emitter ends to ground. connect all the commons to ground. connect all the earths to ground. THEN connect your supply, in this case, PNP transistors, you want 'positive ground'. so connect the battery plus/red to the ground/common/0V line, and the battery minus/-/black to Vcc, at the top. job done, easy.

you have it partly drawn correct, except you have named Vcc all along those bottom point, which should show the ground symbol. your switch as drawn should work correctly. we have to be sure as drawn is as built - there lies the rub.


I'm pretty sure this board/supplier/kit/build has come up a few times in the past. I though somone - either Pink Jimi or Cozybuilder - took the whole thing apart and traced and corrected a circuit diagram and parts placements to fix/suit - and posted a thread on it. but I haven't searched for it.

Yeah, that schematic is not the correct fuzz face circuit, but it is a true reflection of the PCB, hence the root of the problem. You'll see in my earlier photo that I mutilated the board a bit to cut a particular trace so that I could separate those points at the bottom of the schematic from "-9" (shoulda just labeled it that, not Vcc), so that I could then connect them to the "ground", BUT, there is still continuity from that rail back to -9. Hence my plan to just veroboard it and be done with it.

This is what I breadboarded, and it works fine:



Anyway, I see there are some links further down that I'll have more of a read of.

[duck_arse]

your last ^ still shows a lurking Vcc on the volume pot.

[guyshermannz]

Looks like I missed one! An error in the diagram, it is connected to +9 on the breadboard