Author Topic: battery burning up  (Read 3544 times)

mdh

Re: battery burning up
« Reply #20 on: November 19, 2006, 03:26:49 AM »
Pins 4 and 8 look right now. It looks like the resistances are OK, as well. As far as the other voltages go, I'm a little suspicious of the voltages on Q2. It seems to me that they should be more similar to the Q1 voltages, but I could be wrong. I think you're about ready to plug in and see how it sounds. If it doesn't work, the first thing to do will be to swap out the op-amp, and possibly the transistors. If you still have problems after that, you might need to seek help from someone more knowledgeable than I.

Good luck.

jlullo

Re: battery burning up
« Reply #21 on: November 19, 2006, 05:29:02 PM »
mdh and pete,
thank you so much for all of your help this far guys.  i really really appreciate it.

i plugged it in today and there is only the faintest sound when the circuit is on and off.  no difference in tone.  it's barely audible.  so you guys think i should try swapping out the IC and trannys?  wouldn't they be getting different voltages if they were dead?  also, since my LED still isn't working, but isn't burned out, do you think that i still have a wiring problem? 

i'm really stuck and don't know what to do.

just to be clear, if you are looking at the back on a stereo jack and the terminals are on the bottom, they go in the order of shield, ring, tip, right?
« Last Edit: November 19, 2006, 06:25:43 PM by jlullo »

mdh

Re: battery burning up
« Reply #22 on: November 19, 2006, 08:17:31 PM »
i plugged it in today and there is only the faintest sound when the circuit is on and off.  no difference in tone.  it's barely audible.  so you guys think i should try swapping out the IC and trannys?  wouldn't they be getting different voltages if they were dead?  also, since my LED still isn't working, but isn't burned out, do you think that i still have a wiring problem? 

So you know that the LED isn't burned out because you've tested it outside the circuit? If that's true, then you must have some sort of wiring problem if it isn't working. If you used sockets, and you have another IC and a couple more transistors, swapping them should be easy, so that's a good thing to try.

Quote
just to be clear, if you are looking at the back on a stereo jack and the terminals are on the bottom, they go in the order of shield, ring, tip, right?

I don't think there's a simple answer to this, as it depends on the jack. Luckily, it's easy enough to check the connections with a multimeter. For an open frame jack, just put the multimeter on the lowest resistance setting, touch one probe to the sleeve, and touch the other probe to the solder lugs until you get a reading of zero (or nearly zero) resistance. Your multimeter will probably beep when it shows resistances under 2 ohms or so. Repeat for ring and tip, and you should be able to tell which lug connects to which jack contact.

Another general rule for open frame jacks is that the lug is usually opposite the contact that it is connected to. That, and you can generally see which lug is connected to the sleeve.

As a general comment, it sounds like you're a bit overwhelmed because you're debugging a circuit that may be a little complex for your current level of knowledge. It may be a good idea for you to set the Tube Screamer aside for awhile, before you feel tempted to hack it into little bits, and build something a bit simpler. A simple booster such as the beginner project on this forum or a simpler distortion such as the MXR Distortion+ (layout at Tonepad) may give you a higher probability of success and some sense of accomplishment. Plus, you'll get practice soldering and doing the offboard wiring, which is much the same for just about any circuit you'll want to build.

If you're determined to get the Tube Screamer working before moving on, you'll need to at least learn to step through the circuit with a continuity tester (your multimeter on the lowest resistance mode) to check for shorts. If you find shorts that shouldn't be there according to the layout or schematic, then you need to track down what's causing them. This could be a solder bridge on your pcb, incorrect offboard wiring, component leads touching, or (least likely) a shorted component. Unfortunately, we can't find these things for you by remote, we can only give educated guesses as to what the problem may be.

jlullo

Re: battery burning up
« Reply #23 on: November 20, 2006, 11:37:10 AM »
mdh,
haha i am most definitely in over my head, but i haven't lost patience with this yet  :).  i feel like i'm convinced there still is a wiring problem with my offboard wiring.  i'll try swapping out the trannys and the opamp and see what happens.

i'm sure that this is a lengthy process, but how do i test the circuit for shorts?  where do i find the list of correct continuity readings?  do i just go by what the component value is?

thanks a ton.  you've been really patient and helpful with me!

mdh

Re: battery burning up
« Reply #24 on: November 20, 2006, 01:48:29 PM »
When I say "check for shorts" and "step through the circuit with a continuity tester," I mean to say that you need to follow the path of the circuit with your DMM set on the lowest resistance setting (or beep mode, as Pete put it), and check that the things that are supposed to be connected really are, and those that aren't supposed to be connected aren't. You can do this by printing out a reversal of the pcb transfer image (copy and paste it into some graphics program and flip it horizontally, so that the lettering is no longer reversed). Now you have an image of what the pcb traces should look like from the copper side. If you inspect the board with this image as a standard, you might even see a solder bridge just with your eyes. Failing that, you should start looking for adjacent traces that shouldn't be connected but are. This is particularly likely to happen near IC and transistor pins, but can happen anywhere where you have solder pads that are closely spaced. You check for continuity (that is, a short) by touching one probe on one trace and the other probe on the other. If you see a low resistance (zero to less than 10 ohms) and/or your meter beeps, then you have a short. If it shows a substantially larger resistance, or an out of range indication ("O.L" is a common out of range indication on DMMs), then you're probably OK, and can move on to other traces.

You should also check from the component side of the board, using the component overlay view from the layout as a guide, to make sure that the component pins that should be connected really are. This is mainly to check for cold solder joints, solder joints that aren't actually making reliable contact with both the board and the component. And don't forget to verify that offboard components are connected to the correct points on the pcb.

Also, I took another look at your photo from the pictures thread (http://www.diystompboxes.com/smfforum/index.php?topic=36392.msg385425#msg385425) and noticed some things. First of all, a lot of your solder joints look kind of blobby. These are likely to be cold joints, and in some cases may also cause solder bridges, because they contain more solder than is necessary to make a good joint. I would pay special attention to these joints, and in many cases it would probably be a good idea to reflow them by first touching your soldering iron to the pad close to, but not necessarily touching the solder. Once the solder begins to melt, you can move in and make sure that your iron tip is touching both the pad and the component lead. This is the only way to ensure a good joint. In some cases it may be necessary to remove the solder from a joint and start over. If you don't have a desoldering tool of some sort, get one. Finally, I also noticed that a couple of your (presumably ground) connections appear to be connected to each other, but possibly not the rest of the circuit. I'm talking about the connections that are soldered on the lower edge of the board in your picture. It looks like one of them goes to the DC jack, and the other (I'm really guessing on this one) to the ground on the output jack. You have them soldered to a trace that was the outline of the pcb transfer image, and is not connected to anything. Without actually interacting with the board myself, I can't tell whether they're actually connected to anything, but I thought it was worth pointing out. Furthermore, this really is not a reliable way to solder wires to a board, even if the trace were connected to something, or if one of the components was connected to the appropriate point by some other means.

Finally, I would recommend that next time you test the circuit for sound, you do so with the lid off. I recently had tons of problems boxing up a Phase 90. It worked fine without the lid, but with the lid on, there was no sound when the effect was active. Something was shorting out, probably against the flange of the lid, but it was incredibly hard to troubleshoot. Get it working out of the box first. It also may be useful to lift the board up a little bit to guarantee that no components are making contact with the exposed contacts of the open frame jacks (and be aware that they move when you plug in).

jlullo

Re: battery burning up
« Reply #25 on: November 21, 2006, 12:10:16 AM »
alright.  i'm going to figure this thing out.  today i rewired my jacks, and now i'm getting sound when the pedal is bypassed... sort of.  it cuts in and out- but it's still progress!

I'll let you know how it goes.  if you haven't heard from me in about a week or so, call my parents.  I'm most likely hanging from the basement ceiling.

you're the man for all of the help.