Debugging Question

[zener]

Hey guys,

I just did as what you said with the Audio Probe in another thread. Just after 3 components from the input of Doug Hammond's Hot Silicon, I came into a capacitor where the signal (guitar sound) is gone. I check out the solder and side looks fine to me but still, I trace the whole lead with solder. I probe it once again and still there's nothing I cut the capacitor's lead and directly place it in one of the transistor's where it is supposed to connect to. Still nothing. Am I supposed to get a sound at least to the capacitor lead, right?

Is that what you call cold solder joint?

When you can probe the signal from input to output, does that mean that the circuit is working?

What can cause cold solder joint?

I found it weird. Three days ago, my circuit is in the breadboard and it worked. After playing it today, there's nothing. I soldered everything in the PCB, there's nothing.

I still have another one in a PCB two days ago that worked. After two days, I decided to put it in a box. The sound is gone. I probed it and loss the signal in a  capacitor somehere about quarter way in the signal path.

Is there a way for a solder to lose its conducting capability?

Are capacitors sensitive coldness? (maybe a stupid question)

I hope you won't get tired answering my newbie questions.

Thanks.

Zener

[nightingale]

hello zener~
caps block DC... but depending on he circuit layoutand cap size, you may or may not get any signal/sound on your probe...

exapmle:
lets say you have a 4.7uf electrolytic cap... if you are debugging a circuit and you measure .65v on the + side of the cap, and .65v on the - side... you know that the cap is shot...

also:
in my experience it's pretty good practice to make sure every part that is grounded, actually measures 0v where it is supposed to...

the way i learned to debug, was mostly trial and error... but what really helped me the most was the beginning was reading: "how it works" at the geofex site... some of it will be over your head... but if you keep it on the backburner and read it a couple times... it is very helpfull!!!

debugging a circuit is alot easier if you understand electrically what the parts are doing...
hope this helps,

[petemoore]

And still do everytime I try find ways to apply the DMM to a ckt.
 I find this is very helpful...thinking of every possible way to apply the DMM to a ckt., Switching back and forth from different DMM settings as I go through the ckt so I try to hit every 'angle' without losing my place...following the logical path of the schematic.
 I can spend many long times looking over a [just eyeing, compared to schem] ckt then find a miswire.

[aron]

After two days, I decided to put it in a box. The sound is gone. I probed it and loss the signal in a capacitor somehere about quarter way in the signal path.

hmmm. Perhaps it is shorting in the box?

It could be a bad solder joint. The lead might be corroded or the pad might be.

Please tell us the component number that you are having problems with:

http://home.cfl.rr.com/dbhammond/GS_Tonebender.gif

[zener]

After two days, I decided to put it in a box. The sound is gone. I probed it and loss the signal in a capacitor somehere about quarter way in the signal path.

hmmm. Perhaps it is shorting in the box?

It could be a bad solder joint. The lead might be corroded or the pad might be.

Please tell us the component number that you are having problems with:

http://home.cfl.rr.com/dbhammond/GS_Tonebender.gif

Actually, the Hot Silicon is the one in the breadboard three days ago. I've never put in the box yet, only soldered in a PCB. The one I attempted to put in the box is the Ross Compressor that work two days ago but is dead (or probably in coma) now.

With regards to the Hot Silicon, it's the C3, the .1uf after Q1. The last part I had signal is in the base pin of Q1. I had signal with the two input cap, R1 and the base (2nd pin) of Q1.

Thanks.

Zener

[nightingale]

zener~
also might not be a bad idea to gently twist the board... and see if you get any sound... this is a pretty good way to find a broken trace/pad in my experience... but i think aron is on to something... the circuit could be shorting/grounding out someplace... also check the jacks, if any "lugs" besides the ground lug are touching the enclosure anywhere... it will short out the circuit... trust me! i learned this one the hard way...
hth,

[zener]

I forgot to mention, the Ross comp worked intermittently last night (or early this morning) with some few and slight twist of the board before it went into coma. Something loose, maybe. I just decided to etch another board, the one in GGG. I'll get back as soon as I finished building it again.

The Hot Silicon is what intrigues me because after three days in a breadboard, it didn't worked. I check for some loose wire and shorted leads and there were nonw. I just decided to soldered it in PCB.

I don't know if there's any layout out there for it aside that from Bill_F.

Thanks and Happy New Year.

Zener

[Bill_F]

Hey Zener,

Did you ever get the gain pot figured out? Mine still won't do anything and I've looked at the layout again and again and can't see anything I've done wrong. Strange!

Bill

[petemoore]

Doin' my first PCB builds a few weeks ago, I found a spot where 6 leads from components, and a large coppertrace of the PCB all are to be soldered...I did them one at a time...till I de-de-bug-bugg-ed ed it...for a couple days.
 I had to add heat till ALL the metals at those connections 'took' the solder [all at the same time] ...the project started working consistently then.

[zener]

Hey guys.

I finally got my Ross Compressor and Hot Silicon working already .  I boxed them right away. After etching new PCBs, desoldering and soldering, they are now alive and shaking our wooden floor :twisted: .

I used the layout from GGG for the Ross. The one in tonepad is so small that all components are compresses to each other. I wasn't really able to determine what went wrong with the first one, probably loose solder or wiring.

For the Hot Silicon, i used my own layout. Even before doing it the second time, I noticed something unsual with my first build. The battery is hot. I looked at solder side and I a hair-thin copper trace shorting the 9v trace and ground. :shock: . i didn't know if that was the only problem I have but now, they are woking already.

The incident of soldering everything in the PCB, having it worked, leaving it for few days and afterwards, there's nothing happened to me twice already. I didn't know if this make any sense at all but my theory is that the solder and/or the copper traces loose their conducting properties when exposed to open air, especially cool air for quite some time. Is there a coating or any liquid I can use to protect my copper traces and solder joints? Is that lacquer thinner?

Thanks everyone for the answers.

Zener