Voltmeter, fried resistors, capacitors-noob

[bdrobik]

How do you use a voltmeter to determine if a resistor/capacitor is fried or just not properly soldered? I have looked at the dugging sites and had no luck finding an answer. My circuit won't work (obviously) and I am having a heck of a time figuring out what part or solder joint is faulty? Any help using a voltmeter to determine what is wrong would help. I really have no idea how to use a voltmeter! Thanks

[demonstar]

Welcome to the world of DIY effects!

OK lets starts at the beginning...

What circuit are you building?
Have you got a link to the schematic?
What are you building it on: PCB? stripboard? perfboard?
If you used stripboard or perfboard have you made your own layout or copied one?
Have you changed any values from the schematic?

Once we've established that we can start to help.

Here's a link to help with the multimeter...
"http://www.doctronics.co.uk/meter.htm"

Another thing most circuits don't work perfect the first time they are fired up; especially a first build so don't worry and feel too disheartened if it takes a while. Hopefully soon you'll have it up and working!

[bdrobik]

Demonstar-thanks.
I am building Dragonfly's Campanion Fuzz on vero. No changes to values listed. At one point I had volume and no fuzz, I thought I found the problem using my voltmeter and now nothing works. Guess I fixed it all right...
Thank you for the link. I will keep trying.

[demonstar]

O.K. we got something to work with now.

Would I be correct in assuming your using this layout then?

"http://www.aronnelson.com/gallery/main.php/v/DRAGONFLY-LAYOUTS_0/album18/album144/SHIN_EI_FY2_001.jpg.html"

and this schematic...

"http://www.generalguitargadgets.com/pdf/ggg_secf_sc.pdf"

A few more questions now...

Have you socketed the transistors?
Did you cut the tracks of the vero in the correct places?
Is the LED indicator working?

Can you measure the DC voltages at each pin of the transistor? So we'll need...

Q1. collector =
Q1. emitter=
Q1. base =

Q2. emitter =
Q2. collector=
Q2. base =

Also check if the power is getting to the board.

To do what I've said above you need to read that page on the multimeter then when you know how to use it. In order to take the above readings put the black lead on the -ve side of the battery and touch the points I listed above with the red probe and note down the readings.

For now lets assume all the passive parts such as the resistors and caps are working just nicely (eg not blown or shorted) as it is much more likely there is a slight mistake in following the layout or a soldering error etc.

Here are a few other things to be doing...
1)Keep going over and over the layout and checking it copared to the board you've made.
2)Check for solder bridges. this means make sure that there is no solder that has gone astray and joined tracks or components that shouldn't be connected.
3) Check for cold solder joints. I believe this is less likely the problem but sometimes it can be. To check just re-heat all the solder connections and allow them to cool again.

At one point I had volume and no fuzz

It is quite common to get sound out even in a circuit that can have quite a few mistakes in it.

Anyway, carry out lots of step one, check step two and post the voltages and then I'll see if I'm able to help and others will proably chip in at that point too.

There are just so many things it could be at this point it's just a case of checking and checking and gradually eliminating possiblillities.

Maybe read the debugging thread again and search for other debugging threads. The above should get you going though and get you to a place where others can help you!

[bdrobik]

Demonstar-again thanks for the help!

Yes those are the schematics & layouts that I am using. I have not used the GGG one much other than a quick once over.

1. I have not socketed the transistor. Do you reccomend this practice?
2. Traces are cut in correct locations.
3. I did not use an LED.

Power is getting to the board at 9.3 V

Q1 c: 9.2
Q1 B: 7.6
Q1 E: 0.0

Q2 C: 8.1
Q2 B: 0.0
Q2 E: 0.0

Ok. I am guessing these measurements are not what they should be in order for this to be working correctly. ( I am basing this off the examples used on the debugging page). So according to the debug page a resistor isn't soldered correctly??
I will reheat joints in the meantime.
THANKS AGAIN!!

[demonstar]

I would definitely recommend socketing transistors in the future. It protects them from the heat of soldering them in as they are particularly heat sensitive. It also allows for versatility by allowing you to swap various transistors in and out easily.

What transistors did you use?
Are the pinouts certainly correct and orientated the right way around?
(I'm hoping it's one of these things you've done as they are an easy fix and I'm not sure about the stuff below much. If these two steps don't work though you might as well try the stuff below.)

After checking the two things above.
Those transistor voltages seem to be all over the place. I'm not really the best person to be helpping loads at this stage but for Q2 I think check that the R1 (2M2) is certainly in the right place and is soldered properly.
Do the same for C3 and C4.
Thats all I can suggest for now.

Just keep checking and checking and checking against the layout.

Thats all I can suggest for now. I only learnt about that particular transistor configuration the other week. (It was also my first transistor configuration i learnt about)