Rangemaster - No sound

[bamadan5]

You could have a bad joint.  Before soldering up an etched board, it should be cleaned and buffed.  I use a scotch brite pad and lightly scuff the board then I'll clean it with acetone.  It really helps the solder melt onto the copper.  I can tell from your joints that you are not getting good adhesion to the board.  They should be like a Hershey kiss not a chocolate ball. 

Josh

That's good to know. I have a few more etched boards that I'm wanting to work on this weekend, so I'll do this. This is my 3rd build on an etched board, and the others fired up the first time, so I never thought this was an issue. Is there anything that I can do, short of either starting over or buying a new board, to fix this one, if the joints are the cause?

[gtr2]

Check continuity of the two joints in suspect.  You should not have continuity between those two. 

This isn't a complex circuit, you'll get it worked out.  No need to start over    Check out the possible solder bridge before going further.

Josh

[mgwhit]

You're correct about the pads within each circle touching each other -- that's fine.  What I was trying to say is that it looks like the solder globs in the yellow circle might be bridging to the ground plane -- the massive area of copper that makes up most of the board.

I can't tell from the photo if it's really bridging -- it might just be a piece of the component lead sticking into view -- but you can tell by doing a continuity test or just close physical inspection.

The blob in the red circle could be touching the ground plane, too, but continuity to ground there wouldn't make the effect silent.  (In fact, bypassing R2 and C3 might make it insanely loud!)  Continuity from the yellow circle blob to ground, would, however, result in a completely silent effect, as the guitar signal would go straight to ground before it could be amplified by the transistor.  Good luck!

[bamadan5]

Sweet. Thanks for the replies guys. I'll give all of this a shot tonight once I get home.

I seriously need to read up on how to troubleshoot these things before running the the boards here. I just have no clue (yet!) on what should have continuity, what shouldn't, etc.

[bigmufffuzzwizz]

I just have no clue (yet!) on what should have continuity, what shouldn't, etc.

The way you know is by using both the schematic and the layout. For example w/ the rangemaster here, all ground pads are gonna have continuity and same w/ the components connected to the voltage source. From the beginning, the In pad is gonna be connected to one side of C1 and also C2. If you look at the layout you should see what I mean. Your not gonna be able to measure continuity through a components (except for a low ohm resistor like 1 up to about 100 ohms). The other side of C1 connects to the base of the transistor, as well as R1 and R3. If you follow the schem you can see what should and shouldn't have continuity..make sense?

I agree with mgwhit, it looks like the joint in the yellow circle is touching the ground plane. That'd be a good place to check for continuity. I'd also clean up some of the other joints..You might need to use a little more pressure with the iron to achieve better heat transfer. You wanna make sure your applying heat to the pad and the lead.

[bamadan5]

Ok. Update. Slightly good news.

I get a VERY faint sputtery sound with the volume turned all the way up. The pedal still pops LOUDLY when turned on. I've rotated the transistor around 3 times now, and even tried another. The current position is correct, per the datasheet, and I also get zero sound in the other two positions.

I reflowed all joints, and also corrected a few to work better. There is still one "glob" and after about 5 solder/desolder attempts, I don't believe it can be fixed. Its not touchin the ground pad, I checked.

Anyway, more pics below. Any further thoughts are appreciated. I'm going to work on a Neutrino project while I lay this one to the side. It's blowing my mind.

[bigmufffuzzwizz]

Looks much better!! There's about 3 joints that connect to ground (R1, R2 and the other is the ground pad) that look like they need to be heated a bit more. When your ready to give it another chance try that. 

[bamadan5]

You're a psychic. I hit the 3 pads you mentioned and it fired right up!
Only thing now is the LED isn't lighting, so I'm guessing I just got the polarity reversed. I should be able to fix that, I hope. I swore I check it 10 times, but i must be wrong.

[jkokura]

If the polarity has been reversed it might have been blown. Also, if you didn't use a current limiting resistor (commonly at 4.7K) in series with the resistor that will blow it as well. If you have a spare try using that.

Glad it's working! It's frustrating I know, I've debugged a very large number of circuits. I have only had one beat me (and maybe another I'm currently working on will also beat me, though I don't think it's my fault...).

Jacob

[bamadan5]

Well, it appears I spoke to soon.

Now we have sound, and it works, but only the last 10-20% of the pot is actual "boost". Anything lower than about 3 o'clock on the pot is less than unity. With the pot at max, strumming hard on one chord causes the pedal to "flub" and it barely produces any volume for a few seconds after that.

[jkokura]

That sounds like a bad bias... Is there a trim pot on the board?

It also sounds like you could have a problem with your transistor - are you certain of it's orientation?

Jacob

[bamadan5]

No trimpot on this board. I just again turned and reoriented the transistor to every possible position as well as 2 other OC44s that I have all with the same results. No idea where to go from here.

[bamadan5]

This just hit me... I'm wondering if there's something weird with the pinouts of the OC-44 that I have. maybe i need to cross a leg or something?
Anyway I can tell. I was looking at a random OC44 datasheet, but it might not fit for this one?

I got these OC44s from Mammoth a few months back. Markings on the package are "GT-OC44." Markings on the transistor itself are: NJS1045 OC44

Is there any other way to check what the C,B,E are? Anyone know off hand what they are for these specific trannies?

Other thought, is the fact that I'm getting -9.4v an issue? Is the .4 causing an issue?

[jkokura]

Well, the first place I'd begin at this point is back at the beginning.

Double check that all your parts are the right orientation, the right value, and that you are getting -9ishV at the power in to the board and 0V on the GND connection. Getting voltages at each transistor leg is helpful also.

Jacob