Still going through my unfinished project box....
Another fuzz face.
When I made my first Ge Fuzz I breadboarded it before stuffing the board. I had three fuzz face tranny sets and tested them on the same breadboard layout, all good.
I populated two boards and two charge pumps, boxed one up with a pump and left the other in the to do box.
I boxed the second one up today and oh poops it doesn't work.
The bypass worked fine.
The indicator LED does not function.
When the effect was on, no noise unless at full volume and full fuzz. Then I get a very quiet spluttery fuzz when I hit a string.
So first things first, I went to the bias trimpot. The collector at Q2 remains at -8.9v no matter where the trimpot is moved to.
I removed the trimpot and found no error with the trimpot.
So the things I have tested so far are as follows:
The charge pump is functioning normally. ~+9v in, roughly -9v out. Tested against all available ground points. all good.
(http://i1298.photobucket.com/albums/ag43/buzz134/FFPNPabc_zps20c00b23.jpg) (http://s1298.photobucket.com/user/buzz134/media/FFPNPabc_zps20c00b23.jpg.html)
I'm getting -8.99v at A.
Here's where some funny business starts, between B and C, with the trimpot removed, I'm getting a resistance of around 40k. Shouldn't that be an open line?
Is this an indication of transistor failure?
I know the standard gig is to provide a photo, but it's sticking halfway of of the box and I can't get a good one.
This is my power setup for the charge pump. It's worked so far in a tonebender and a FF.
(http://i1298.photobucket.com/albums/ag43/buzz134/Inverter2_zpsb15f53eb.png) (http://s1298.photobucket.com/user/buzz134/media/Inverter2_zpsb15f53eb.png.html)
And a link to the schematic...http://www.generalguitargadgets.com/pdf/ggg_ff5_sc_pnp.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a (http://www.generalguitargadgets.com/pdf/ggg_ff5_sc_pnp.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a)
try reversing yr probes across B and C, see if yr 40k changes. and did you point your led the correct way, seeing as you ground voltage has been "reversed"?
Yeah, I may have reversed the LED, haven't checked but not a big issue atm.
I tried reversing the probes and did get different results With the black ( com ) probe on Point B i get 37.6k
With the red probe on point B I get 42.7k.
Did it a few times, same result.
But it doesn't give the full reading straight away, takes a few seconds to creep up to the reading before steadying out on the final number, starting out on just a couple of ohms to the 42.7k, starts out at about 16k the other way 'round.
try measuring resistance on your transistors... i'm not sure but the measurement you're getting sounds a lot like R2, R5, what ever is dialed on your trimmer and what is left of the transistor resistance in series. I'm worried about Q2 and that C and B are shorted. you can find out by measuring resistance between B and C leads and then reverse your probes. Because there is a diode inside you will get a very low resistance one way and a very high resistance the other way, because a diode conducts only in one direction... if your transistor is blown you will get very low resistance both ways meaning the signal will go freely through no matter what and that part of the transistor is reduced to a simple jumper with maybe some small resistance.
also try measuring B and E the same way on Q2... and just in case measure Q1 too. If your multimeter has a diode measurement function, use that. Probes one way you will get a forward voltage of the germanium diode inside... it should be around 0.7 V, probes the other way should read infinity. If you get reading that is much less than 0.7 V and a reading both ways, the diode inside is fried... sometimes it is easier to use continuity mode and not concentrate on readings too much... the multimeter will beep if it finds a short. but diodes sometimes can short to a state that still has enough resistance that the continuity mode on the multimeter will not recognize as a short, because in reality continuity mode is just measuring resistance and if the resistance is low enough, usually lower than 5-10 Ohm it will beep.
Also the fact that you wont get the reading right away means that there is a capacitance somewhere that starts charging when you measure, but nothing seems to be between the path you use to measure.
Also check really hard if you maybe left some pins unconnected or connected to the wrong place etc, verify you build and the double and triple check.
Hope it helps.
also you need to take the transistors out to measure them, i forgot to mention that
Thanks Uriziel.
Unfortunately the transistors are soldered in.
They are AC125s ( if memory serves me correctly ) and are in those really tall tins ( TO-1? ). So in a 1590BB there's not much room, so I soldered them to save the extra height added by a socket.
I'm pretty quick on the iron and use little gator clips as heat sinks so it's usually not a problem, but maybe I cooked one this time.
I think my next move will be to take the board back out of the box, and test it minus DC input jack and charge pump. Like I should have before I put it in the box.
If I still can't get function then, I'll desolder the trannies and test them.
And lesson learned.... sockets.
I did see a good thread on here about making sockets by drilling out the holes in the board to fit IC pins. Nice and low profile too. Going to have to make that a habit, especially with Ge trannies.
Edit: And yes to Duckarse. I did have the negative lead of the LED connected to ground. Knew I had to reverse it but somehow habit must have taken over :P
> collector at Q2 remains at -8.9v no matter where the trimpot
No-connection at Q2 Emitter is a strong bet.
Voltages throughout (not just hilights) might be clue-ful.
Hi Paul.
I'll pop the trimpot back in and come back with a full set of voltages for both trannies.
Avoiding the soldering iron tonight though.... my latest homebrew ale has turned out to be a particularly tasty batch. :icon_biggrin:
Quote from: Buzz on October 18, 2013, 06:57:57 AM
my latest homebrew ale has turned out to be a particularly tasty batch. :icon_biggrin:
yay, another real ale brewer...that first taste of a new batch ..nice, enjoy.... ;)
Quote from: deadastronaut on October 18, 2013, 08:09:52 AM
Quote from: Buzz on October 18, 2013, 06:57:57 AM
my latest homebrew ale has turned out to be a particularly tasty batch. :icon_biggrin:
yay, another real ale brewer...that first taste of a new batch ..nice, enjoy.... ;)
Greetings brew brother! Real Ale is a beautiful thing!
Some more voltages....
Battery 8.86v
Board in -8.84v.
Q1
E: 0v
B -105mV
C -356mV
Q2
E -367mV
B -358mV
C -8.75v.
????
Quote from: Buzz on October 18, 2013, 11:50:05 PM????
Indeed. Multiple wrongnesses and I'm not seeing a clear pattern.
40K leakage on Q2(?) is not for-sure wrong in Ge, but I'd start chewing there. Get another Q2. It can even be Silicon, but must be PNP. (If that works better, Q2 will force Q1 to adapt to the higher Vbe of Silicon Q2.)
But the large drop in the 100K makes me wonder if Q1 also has a problem. (Sadly we can't drop-in a Silicon at Q1 without multiple other changes.)
As always: get it out in the open, bright light, sharp eyes (or magnifier). Shorts, opens, bad joints.
How sure are you of your pinouts?
Can you get the previous build open and compare voltages and parts?
Thanks Paul.
To simplify I'm going to pull the board out of the box, disconnect the DC in, charge pump and stompswitch. I'll just run it off a reversed 9v battery.
To hard to get a good eye on the back of the board while it's in the box.
I've just ordered some IC socket strips so I'll wait for them to arrive to proceed, then follow your advice.
By then I'll be looking at it with fresh eyes. That's always an advantage too.
homebrew you say, buzz? and in australia, you say? and a problem w/ a trimpot, I think you mentioned. I'm certainly now interested, if of no use ....
and sharpening, you mentioned?
Mr Duck!
I see you are in Sydney too.
I've ( come close to ) perfecting a beautiful British Real Ale, All easy to find ingredients, super easy recipe. So yep.... homebrew.
Sharpening? you can shave with my kitchen knives. I was great with chisels too... until my 3yo combined my whetstone and my fretsaw, he was *fixing* it.
It is certainly fixed now. Can't be angry, the little bugger wanted to help, and wanted to be like dad. Awwww...
But hey, chuck us a PM. We can meet up in an appropriate boozer and share our common interests.
At least you know my eyes won't glaze over when you discuss the comparative tonal differences between using 1N34a Ge vs 1N4148 Si diodes as clipper pairs... lol.
I'm busting to talk chisel sharpening with someone. I've just found how much damage I can do to a piece of wood with a chisel, especially if I've just managed to put a good sharp on it. trouble is, I seem to take the sharp off as much when I try to sharpen, and this just adze to my problems.
do you only beer, or do you cider as well?
diode clippers? mmmmm, well.
Have fun boys.:)
OK, it's not the trannies.
I desoldered them and gave them the diode test as Uriziel suggested, and they worked.
Then I realised I hadn't marked them before taking them out. Derp.
So I hooked them up on the breadboard with RG's transistor tester.
The first came out at 82 hFE with 172ua leakage. The second with 109 hFE and 260ua.
( Note to self.... I marked the 82 hFE! it's Q1! )
Well, double tested and shown to be working.
I've just started etching my own boards and have a nice FF board ready to go.
I think I'll build it in that and do a post mortem on the other board. I'm interested in where I stuffed up. I bet it's something real stupid....
Hey Buzz,
I wonder if increasing that collector trimmer would help you bring down that 8.9v? 40k "should" be fine but maybe it needs more? Or test it with another, 20-40k resistor in series wit it, save ordering / waiting for a new one.
Paul
Hi Chromesphere.
Maybe I should get it hooked up on the breadboard while I'm waiting for my socket pins.
I'll see if get the same problem there, if so I'll just keep upping the resistance and see if I can pull down the 8.9v.
At the moment I've got the transistor tester on the BB, so I might go through a stash of Ge trannies Brett kindly sent my way and get them sorted for projects.
The FF trannies are in the range of acceptable gains and leaks, I really think there was a fault in my build causing the problem.
(http://i1298.photobucket.com/albums/ag43/buzz134/FFPNPabc_zps20c00b23.jpg)
here's a question: your diagram does not show a marked connection for "F1". you do have your fuzz pot connected to ground, yes?
> you do have your fuzz pot connected to ground, yes?
> Q1
> E: 0v
> B -105mV
> C -356mV
> Q2
> E -367mV
> B -358mV
> C -8.75v
I'll be dinged. That _could_ explain it.
Hi Guys.
The Fuzz pot ground is connected to the volume pot ground.
The full layout is here.
http://www.generalguitargadgets.com/pdf/ggg_ff5_lo_pnp.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a (http://www.generalguitargadgets.com/pdf/ggg_ff5_lo_pnp.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a)
Both lugs have zero resistance with the board ground.
That lead me though, to find a possible culprit.
The ground wire connecting the board to the output jack looked a bit dodgy at the board end. Wiggled it... snap.
It was just hanging on by a couple of threads.
It is possible this could have been caused by my lifting the board in and out so many times. Another possibility is that during the build I have re-flowed the solder while attaching one of the other grounds, causing this one to slip out a bit, leaving me with an insufficient ground connection.
That would explain the weak spluttery fuzz while the effect was engaged. It would also fit that the bypassed signal was unaffected, as the input and output jacks have a wire connecting their ground lugs.
But would that cause any problems with the bias trimpot?
This also lead me to find another fault in this build, which also applies to my last four builds.
Lately I have been using input/output jacks like these:
(http://i1298.photobucket.com/albums/ag43/buzz134/Jack_zpsb5698711.jpg) (http://s1298.photobucket.com/user/buzz134/media/Jack_zpsb5698711.jpg.html)
They look neat outside and inside, and I like that they are fully enclosed.
They are, however, electrically isolated from the enclosure. I had assumed that the enclosure would be grounded by the stompswitch, which I tested by checking continuity between the stompswitch and the enclosure :icon_redface:
After finding the enclosure on this pedal was not grounded, I checked back over my other builds and they, too, have non-grounded enclosures.
Oddly enough they are quiet pedals.
I'm thinking the solution to this would be to solder a wire between one of the pot bodies and it's ground lug, as one would on a shielded scratchplate in a guitar.
Would that be the best solution?
it would be a solution. have you any fuzz sounds yet?
those ^ jacks bother me, the way the nut works as a screw and has so little to spanner. and I've been caught not paying attention to the way the switching contacts work, too.
Yeah duck, the way the nut threads bothers me a bit too.
No problems yet, but early days, I haven't been using them for long.
As for the solder lugs, I didn't like that setup too much either. Solved it though, I snap off all the lugs on the Switching side ( the ones that get taken out of circuit when you insert the Jack )
I leave the other three lugs intact for the input jack. They work in a nice logical order, Sleeve closest to enclosure, then ring in the middle and tip on the inside. The same order they appear in on the male 1/4 jack.
Then for the output jack socket I also snap off the middle ring lug, as it won't be needed.
I just wiggle the lugs with some needlenose pliers til they break off, then file them flush with the plastic enclosure. They end up looking very neat.
So what I end up with is an obvious input and output jack, with lugs in logical order. Makes wiring a breeze.
The only positive thing I can say about the nuts is that, because the external nut is metal and the female thread is nylon ( or whatever plastic it is ) is that if you put the right amount of torque into tightening them, they bite like a nylock nut and wont come loose. It would be nice if the metal threaded nut was a bit longer. I have no idea about the longevity of the items, I really haven't made any of these pedals do any hard yards.
A big question here is the grounding of the boxes. I haven't had any RF noise problems with these pedals. How important is it really to ground the enclosure ( and make a faraday cage... is that the right term? ) Or if I don't ground them am I really gonna regret it when one day I play in a room with banks of flouro lights?
I haven't gone any further with this pedal yet, still waiting for my IC socket strips.
I don't want to solder or de-solder those AC125's again. Don't want to bake them.
you shoulda said. not only have I got a shirtload of ic sockets here I've never used, but I also bought some (20) of these from rockby recently.
(http://www.rockby.com.au/Catalogue/Jpg/4746_.jpg)
turns out they aren't "the thing" that I need to make all my pedals easy to design/wire/construct after all.
as for grounding cases, mine are pretty haphazard, but they don't get out much. if you make sure all yr metal parts like switches and pots make good electric connection to yr metal case, and return one of them to your board earth, you're most of the way there. using those insulated jacks means one less/one more problem: they won't cause loops, but they will both need earth wires.
I've been running all my wires from wherever, to my mill2 mounted on the footswitch. makes my wiring neater, and hasn't caused any probs. yet.