troubleshooting anomaly almost had me stumped...

[LucifersTrip]

I may be in the minority, but I actually enjoy the puzzle of troubleshooting, which is why most of my posts here are helping others.  It's rare that I have any circuit that takes more than a few hours to get working, if it doesn't right off...and I still have nothing in the "graveyard", nothing broken & nothing incomplete....but this one almost had me.

It's always the anomalies that kill the most time. The last one that took almost this long was when i diagnosed a bad (open) resistor.

Anyway, I built the fuzz section from the WOW Signal Fuzz.


All voltages were right on the money, but I only got a barely audible (almost nothing) output at full volume. Though, I could here an actual fuzz tone. Any time in the past there's a low signal, I suspect a loose connection, jack not pushed in all the way, failing alligator clip, etc. I checked all: negative.

I traced the signal straight thru to the left side of the output cap...still good...but hardly anything on the other side (alligator clip on solder bridge). I checked the cap...good. I checked both resistors on each side of the output forming a voltage divider: both good.

I took a break...

Next time I lucked out. Instead of clipping the alligator clip from the output to the center of the solder bridge between the two resistors that make up the divider, I accidentally brushed it against the joint of the cap & top resistor......sound!

So, I figured the alligator clip wasn't making a good connection with the solder bridge...nope...it was. And then, as a joke I checked the resistance between the two resistors in the divider...open!  what the???  It's a beautiful shiny, joint grabbing the legs of two, new, non-oxidized resistors...





eliminate the impossible, whatever remains, however improbable, must be the truth

edit:
Possibly, not exactly "open". I had my meter set on 2M to check continuity and it showed "1", open. I switched to 20M and it started at 16M and quickly rose > 20M, then showed "1", open. So, it is possible that the connection is not open, but there is a resistance > 20M.

[midwayfair]

I still have nothing in the "graveyard", nothing broken & nothing incomplete....but this one almost had me.

man, I wish I could say the same.

I actually kind of enjoy the troubleshooting puzzle, too, when it's under an hour ... after that, it usually means something's really bizarre. Can't say I've ever encounted an open resistor, though.  But my preferred "puzzle" is creating the layouts. Much easier to fix if there's something wrong. 

[LucifersTrip]

I still have nothing in the "graveyard", nothing broken & nothing incomplete....but this one almost had me.

man, I wish I could say the same.

I actually kind of enjoy the troubleshooting puzzle, too, when it's under an hour ... after that, it usually means something's really bizarre. Can't say I've ever encounted an open resistor, though.  But my preferred "puzzle" is creating the layouts. Much easier to fix if there's something wrong. 

there's nothing easier to fix than a perf that looks similar to the schematic...

I still haven't used any layouts (I improvise perfs after breadboarded & tweaked), so I never have two that are the same.The turkey comp "layout" was made after I soldered, of course.

though, I'll definitely use some type of layout when the part count goes way over 50 and uses multiple IC's

[slacker]

I had a resistor go bad on me once, confused the hell out of me http://www.diystompboxes.com/smfforum/index.php?topic=62605.0.

[Pyr0]

I had a resistor go bad on me once, confused the hell out of me http://www.diystompboxes.com/smfforum/index.php?topic=62605.0.

That's not something you see too often.
Back in the 80's when I worked with a computer manufacturing company, once we got the fully assembled computer working (these were the big mainframes, like multiple fridge cabinets side by side), we used to leave tests running on them for 48 hours to try and weed out faulty components - we called it the burn-in period. It was amazing the amount of brand new components that would fail after a few hours of extensive testing.

[LucifersTrip]

I had a resistor go bad on me once, confused the hell out of me http://www.diystompboxes.com/smfforum/index.php?topic=62605.0.

the first time that happens, it does surprise you. the one that first killed me was completely open...dead, and it didn't go bad. It was bad when I soldered it (I didn't breadboard beforehand), which is why I now check each component a final time before soldering to the board.

I've had one other dead resistor after that, a few dead pots and no caps, yet...all before using the pedal. After using, I've only had pots, leds & silicon transistors die (amazingly, no germanium deaths yet)

...and this was definitely the first bad solder bridge

[PRR]

> Possibly, not exactly "open".

My eyes see no proof the left resistor leg is "wet" with solder.

It almost looks like a little crater around the leg, though that may be the light.

This happens a lot. Had an expensive IBM/Samsung monitor. Worked, then didn't, worked if slapped, then slammed... hand got tired so I opened it. Took a while. There was a PCB with a heavy pin for power inlet. The dip-bath didn't get the pin HOT. Either from tight fit or solder-whisker, it worked through final test and for several years. But there was dark line all around the pin, and that ain't solder. Put my big iron on, took solder off, scraped the old metal, re-soldered, worked fine for years.

[LucifersTrip]

> Possibly, not exactly "open".

My eyes see no proof the left resistor leg is "wet" with solder.

It almost looks like a little crater around the leg, though that may be the light.

It is actually the light...It's not perfect, but that's the first thing I looked for. My eyes are still amazing for small stuff. I can still read the numbers on smd resistors...and only use a 40 watt iron, even for the small stuff.

This happens a lot. Had an expensive IBM/Samsung monitor. Worked, then didn't, worked if slapped, then slammed... hand got tired so I opened it. Took a while. There was a PCB with a heavy pin for power inlet. The dip-bath didn't get the pin HOT. Either from tight fit or solder-whisker, it worked through final test and for several years. But there was dark line all around the pin, and that ain't solder. Put my big iron on, took solder off, scraped the old metal, re-soldered, worked fine for years.

On this one, I couldn't even get any connection jiggling either resistor. I would've expected something since the legs were new & shiny.

Oh yeah, one other thing I didn't mention. I thought the problem may have been a short on the other side of the board, but again not the case

edit:
it was also "open" at 2M dmm setting from the center of solder bridge (with alligator clip) to either resistor.