hot battery!

[megg]

I've clearly got something wrong here. This is my third stompbox and although I'm good at following directions for projects, my understanding of electronics needs improvement. I'm pasting the diagnostic steps that I got through before the battery got really hot. I should add a couple things:

a. I am using a radio shack dc jack - 274-1582 - that I very probably wired incorrectly. I have the middle terminal connected to ground, the next one (going clockwise) to the pos batt lead, and the last to 9V+ on the board. I'm pretty sure I did this wrong and that this is the cause of the problem. Anybody know what's what on this thing?

b. I accidentally soldered the 2N5087 into the space for the FET in the bypass circuit. Naturally, I didn't use a socket. I have since pulled it out and put it in the socket, and soldered the FET into its appropriate place. Would the heat damage from soldering the 2N5087 directly into the board break the circuit?

1.Signal gets through when effect is off. No signal gets through when effect is switched on. LED does not light when switched on.
2.Name of the circuit = Brian May Treble Booster
3.Source of the circuit (URL of schematic or project) = http://www.tonepad.com/project.asp?id=40
4.Any modifications to the circuit? No, and I also followed instructions for using on-board bypass, off-board layout #4 from tonepad
5.Any parts substitutions? For C2, used .0047 instead of .005. For C5, used .047 instead of .05. For diode in bypass circuit, used 2N3904 w/ emitter lead cut off.
6.Positive ground to negative ground conversion? Yes - project sheet says board can be used for a Range Master or BMTB work-alike "using negative ground so it's compatible with the power supply of the rest of your pedals."
7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? =>8.4
Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead =? Couldn't get any further b/c the battery got almost too hot to touch within a minute or so.
Voltage at the circuit board end of the black battery lead =?

Now the battery voltage is 8.1.

Thanks!

[Izzy]

Looks like you are shorting 9v to the ground.

[Rodgre]

A hot battery almost always implies a direct short between hot and ground. Check your wiring of the DC jack.

Disconnect the jack altogether, and test continuity between the hot and ground wires you had on the jack. If there is no continuity, or at least high resistance, then the problem is in the jack wiring.

It's also possible that you have the switching on the DC jack reversed, so when you have a DC adapter plugged in, it's connecting to the battery as well!


Roger

[Rodgre]

GOT IT!

The Radio Shack jack is metal. You're shorting right to ground right there. You need to isolate the DC jack from the enclosure, or use a plastic jack like this: http://www.smallbearelec.com/Detail.bok?no=666 .

Roger

[Paul Marossy]

The Radio Shack jack is metal. You're shorting right to ground right there.

I made that exact same mistake on my very first build! 

[megg]

Thanks everyone. Roger, I haven't even put it in the enclosure yet - do you still think that's the problem? (I can see how it will be a problem once I get there, so thanks for the heads up!)

Another thing, the battery doesn't start heating up until I put the phone plugs in the jack.

[PerroGrande]

Check your phone jack wiring.  Many of these pedal configurations use a stereo jack as a power switch.  They are, however, switching the negative line instead of the positive line. 

Whatever you've got going on, it is almost certainly a dead short from the battery + to ground. 

[soulsonic]

Did R1 (100 ohm) also get hot? It may be a short on the board, or possibly a shorted electrolytic cap. If you have one of those meters that beeps for continuity, you can touch one probe to the ground trace, and then touch all the points where the positive voltage would normally be and make sure something isn't shorting. The junction of where C1, C4, R1, R5, and R6 all join together would be a good place to check - a short there could be trouble for the battery. Any meter will work, I just prefer the kind that beeps, because I don't have to look at anything. Make these check without the battery plugged in (of course).

Also, you should see what happens if you connect the battery clip leads directly to the board without the DC jack or the input jack "switching" connection. If it still gets hot with it attached directly to the board, then you know for sure the problem is in the board somewhere - if not, then you know something's up with the jacks.

[oskar]

tery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? =>8.4
Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack...
Now the battery voltage is 8.1.

Thanks!

1. If the battery only drops to 8.1V it doesn't sound that shorted, I think the voltage should drop much more ...especially since the battery is 8.4V
unloaded. (running upstairs) (90seconds later) OK! I just shorted a battery reading 8.5V and it dropped to 0.1V. Test it with a fresh battery.
2. If that doesn't work disconnect the dc jack and drive it from a battery only to start with.

oskar

[petemoore]

  Testing for non-continuity between V+/V- has become a routine pre-PS-test, I like to make certain there are no chances of getting a short under all conditions.

[oskar]

tery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? =>8.4
Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack...
Now the battery voltage is 8.1.

Thanks!

1. If the battery only drops to 8.1V it doesn't sound that shorted, I think the voltage should drop much more ...especially since the battery is 8.4V
unloaded. (running upstairs) (90seconds later) OK! I just shorted a battery reading 8.5V and it dropped to 0.1V. Test it with a fresh battery.
2. If that doesn't work disconnect the dc jack and drive it from a battery only to start with.

oskar

Sorry, I think I got you wrong...     
The 8.1V reading was after frying the battery... It wasn't 8.1V while it ran hot... well, I had jolly good time shorting
batteries. I kind of like those destructive moments.
This means, off course, don't try it with a fresh battery...
You might want to include a nice little picture or two. ( input jack especially )

good luck

oskar

[megg]

Thanks everyone. I switched two of the leads for the dc jack and that helped quite a bit. That is, now signal gets through when effect is on, and battery is not about to explode.

However, how about this oddity (and please, someone, tell me if I'm being an idiot):

When effect is switched on, LED does not light unless - get this - I am dragging the assembly (i.e. the board and all the bits dangling from it, not in the enclosure) to the right across the surface of my wooden table. So: effect on, assembly sitting there, no light. Effect on, I am sliding the assembly from left to right, LED lights momentarily and goes out when assembly stops moving. Effect on, I am sliding assembly from right to left, no light.

[oskar]

When effect is switched on, LED does not light unless - get this - I am dragging the assembly (i.e. the board and all the bits dangling from it, not in the enclosure) to the right across the surface of my wooden table. So: effect on, assembly sitting there, no light. Effect on, I am sliding the assembly from left to right, LED lights momentarily and goes out when assembly stops moving. Effect on, I am sliding assembly from right to left, no light.

Wow, thats some picky diode. Check the wire/track marked ctrl from the output... it's with the millennium bypass right?

[the_random_hero]

Thanks everyone. I switched two of the leads for the dc jack and that helped quite a bit. That is, now signal gets through when effect is on, and battery is not about to explode.

However, how about this oddity (and please, someone, tell me if I'm being an idiot):

When effect is switched on, LED does not light unless - get this - I am dragging the assembly (i.e. the board and all the bits dangling from it, not in the enclosure) to the right across the surface of my wooden table. So: effect on, assembly sitting there, no light. Effect on, I am sliding the assembly from left to right, LED lights momentarily and goes out when assembly stops moving. Effect on, I am sliding assembly from right to left, no light.

Sounds like a loose solder joint that you're only moving when you drag it in that direction.

[megg]

Thanks again for the input. I'll go over the board and look for loose solder joints. I went through RG's checklist (below) although I'm not sure what to do with this info now that I have it. Umm, maybe this is the part where knowing something about electronics would be helpful.

1.What does it do, not do, and sound like? Switched off – bypass working. Switched on – no signal when effect turned all the way down. Plenty of signal when effect turned all the way up. In between, some suspicious noise in the last 25% of the turn (when turning up, that is)
2.Name of the circuit = Brian May Treble Booster
3.Source of the circuit (URL of schematic or project) = http://www.tonepad.com/getFileInfo.asp?id=83
4.Any modifications to the circuit? Not intentionally
5.Any parts substitutions? C2 is .0047 microF instead of .005. C5 is .047 microF instead of .05. Diode is 2N3904 w/ e-lead cut off.
6.Positive ground to negative ground conversion? Yes
7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? => 9.2
Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead = 9.1
Voltage at the circuit board end of the black battery lead = 0

Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Q1
C =8
B =6.05
E = 2

Q2 - bypass
C=0
B=4
E=9.1

D1 - bypass
A (anode, the non-band end) =0
K (cathode, the banded end) =9.1

[oskar]

1.What does it do, not do, and sound like? Switched off – bypass working. Switched on – no signal when effect turned all the way down. Plenty of signal when effect turned all the way up.

The control is a volume knob... All the way down = no sound  = It works as it should...   

...some suspicious noise in the last 25% of the turn (when turning up, that is)

Did you use an old potentiometer? Do you get noise also from just touching the volume knob or is it just bursts of noise while turning?