|
Post by eljib on Jan 14, 2006 17:07:22 GMT -5
I'm just about to begin going through the compressor I made to figure out why it 's not working. I hoping that, with a little info from me, you guys could point me in the right direction for where to start. 1. When checking for problems with a multimeter do I run the risk of "blowing a fuse" if I use the wrong setting? If so, what setting should I use? 2. I seem to remember that infinite resistance means bad connection, and no resistance means short. Is this correct? 3. The battery gets really hot after a few seconds in the circuit. Does this indicate a short? (I don't often hold the batteries when playing, so I'm not sure if they do this normally ) 4. My I.C. came in a static proof container. Could I have blown out the I.C. on accident when I installed it? How could I check for that? 5. My Germanium Diode did NOT come in a static proof container, and I have heard that these diodes are very delicate. No question here, really. I was just wondering if someone could verify that rumor. If so, it will be one of the first places I'll check. I know this is long, but I'm lost. Your help is greatly appreciated. -Aaron
|
|
|
Post by Mini-Strat_Maine on Jan 14, 2006 17:51:04 GMT -5
1. When checking for problems with a multimeter do I run the risk of "blowing a fuse" if I use the wrong setting? If so, what setting should I use? With the battery in (or other power in the circuit), you could look for DC voltage at different points. The real trick is knowing what values you should be seeing at what points. If just checking your wiring ("continuity"), then you'd be checking resistance. Pull the power source, then it's pretty hard to blow a fuse. Infinite ("no continuity") could be something "open," like a switch in its off position, bad connection, etc. And no resistance could be a good thing, if you're making sure there's current flow (a closed circuit) between point A and point B. (In that case, the meter is supplying the current.) That continuity thing again. An IC can get zammed if you pick it up without discharging static off yourself first. Wear a grounding strap or touch a metal water pipe or something. (The strap is better. You could build up a charge running between the bathroom or kitchen and the workbench. ) I think those have to be in the circuit to be checked, and you'd have to know what voltage should show at which pins. Those can be heat sensitive. You have to be careful when soldering them.
|
|
|
Post by JohnH on Jan 14, 2006 17:55:34 GMT -5
I'll throw in a few points, but you'll need to do some detective work to narrow the problem down.
If your battery gets really hot, that is a pretty clear indication that the whole circuit is behaving as a short circuit. batteries dont get hot (maybe slightly warm) when a circuit is working. Until you can solvethat, nothing will work.
Very hard to tell if your IC is blown, if you are not sure if the rest of the circuit is OK.
For poking around in a circuit that is running, a voltage setting is usually best, one lead to ground, then you can test for voltages at various points, if you know what voltages you are looking for.
Did you use a socket for your IC? always a good idea. If so, carefully pull it out (careful of static if it s sensitive to this, depends on the IC). then remove the batteries and test the overall resistance of the circuit, if you get a very low value of a few ohms, you have a short circuit to find.
Diodes can get fried by too much current or heat, but to my knowledge they are not sensitive to static.
If you battery got that hot, it has probably become significantly discharged and may be no good. Test it out of circuit with a voltage setting.
John
EDIT - just noticed MSM posted too while I was writing. Two lots of good advice - should get you moving!
|
|
|
Post by eljib on Jan 14, 2006 22:57:53 GMT -5
I used a socket, and the IC is a JRC4558D. My guess is that its's one that is easily damaged by static, or else the guy wouldn't have shipped it in the anti-static sleeve. But it's not like a charge came off the end of my finger, like when you shock someone for fun.
Also, I've only ever checked continuity using an analog meter, but my dad has that one now and all I've got is a digital one that I have get used to. I'll report back with some numbers.
|
|
|
Post by Mini-Strat_Maine on Jan 14, 2006 23:44:48 GMT -5
I used a socket, and the IC is a JRC4558D. My guess is that its's one that is easily damaged by static, or else the guy wouldn't have shipped it in the anti-static sleeve. But it's not like a charge came off the end of my finger, like when you shock someone for fun. Even though a spark didn't leap across an "air gap" like from your finger to a doorknob (or someone's nose; we saw you shuffling your feet before you went up to them), you can still pass a fatal charge from your body to an IC if you don't take precautions. (It might fatal to the IC. You'll just be highly annoyed when you have to get a replacement for it.) High voltage (maybe 35KV with the "right carpet" on the "right day") but very low amps, so low wattage. BZZZZT! Any of the "DC Ohms" ranges should work; I don't know if it matters which one you set it on. Touch the probes together and watch the needle make a full deflection, all the way to the right. If you measure the path between any two points in the device you're testing, and it does that, you've got pretty much an unbroken electrical path with no or negligible resistance. My wife was impressed yesterday when I used mine to check the fuse in the power cord of her radar detector. Yep, that hair-thin element (2 Amp) was fried.
|
|
|
Post by eljib on Jan 16, 2006 12:56:46 GMT -5
Okay, I got my trusty analog meter back, and I've made a few measurements. Between the input and output jacks there is no resistance in either switch position. On some resistors there is no resistance (this seemed kind of weird to me), regardless of which poles I used to test them. On others, I get a reading of 0 Ohms one way, then switch the leads and get Ohm ranges between 3 to 35. The caps and transistors do the same thing (except now the readings are 0, 35, 275). These numbers do not appear to be random, as adjacent parts have like measurements. Here is the schematic I am using, and a picture of someone else's handywork (my soldering is much cleaner). Hopefully this will make it a little clearer. www.generalguitargadgets.com/diagrams/orangesqueezer_sc.gifwww.generalguitargadgets.com/diagrams/orangesqueezer_lo2.gifwww.generalguitargadgets.com/pics/os_inside.jpgCould someone tell me if it's possible to fry one of the parts I'm using, and in its failed state it acts to short the circuit? As far as the I.C. goes, would my static charge not have been disipated by the anti-static sleeve before I removed it? -Aaron BTW, congrats on your electronic heroics for your wife. I hope you got paid in full EDIT- I am using the setting on my VOM that reads "Rx10,000", if that helps anybody figure out what the hell I am doing.
|
|
|
Post by JohnH on Jan 16, 2006 14:28:47 GMT -5
Its hard to know where the problem might be, but it could be as simple as something around the input jack/bypass circuit. To look for short circuits, a lower resistance setting is better, Rx1 or Rx10.
Heres two things to try: 1. Take the battery out, plug in the input and output leads. Does the bypass switch work, sending your unchanged guitar signal straight to the amp? 2. measure the resistance across the two battery terminals, with no battery there and no leads plugged in. then repeat with leads plugged in. Plugging in the input jack is supposed to engage the power, but if there is a problem with the connections there, it could instead short the battery, resulting inthe heat and no signal that you experienced. This would show up as a very low ohms reading (say less than 10 on an Rx1 setting)
John
|
|
|
Post by Mini-Strat_Maine on Jan 16, 2006 14:48:30 GMT -5
Could someone tell me if it's possible to fry one of the parts I'm using, and in its failed state it acts to short the circuit? I think most electronic stuff goes "open" when it fries, but I could be mistaken. (Although I have heard of contacts on a radio transmitter being "welded" shut by a lightning strike, causing the transmitter to key up until it finally crapped out.) Caps and resistors and pretty much everything except ICs should be immune to static. Heat (soldering) might be a different story. The sleeve really only protects something that's inside it. Once it leaves the relative safety of the sleeve, it needs other protection. (There are those who will tell you that laying a component on the outside of its wrapper for "protection" is a real bad idea.) I think you still should ground yourself before handling anything that's ESD-sensitive, then any potentially harmful charges are sent elsewhere before they can really become a problem. A wrist strap is best, because it's easy to forget to ground oneself out before handling components. (No, I didn't fry anything on my PAiA project, but I probably missed some good opportunities to do so. When it didn't work, that was my first worry.) You may not have cooked yours, but this time of year especially, the (dry) air is full of little malevolent wannabe lightning bolts. Thanks, but she just expects that now. "Guys are good at lifting heavy objects and fixing stuff." That's the multiplier for that setting, so your 35 mentioned above would be 350,000. Then again, without knowing what values (and whether volts, ohms, or whatever) should be at what points, it's hard to say. If somebody can tell you that "with the battery in, you should be seeing +4.5 volts between pins 5 and 8 on the IC" or something like that, then you've got a good "map." EDIT:Once again, JohnH and I are typing at the same time. Hint: His info is probably a lot more useful than anything you'll get from me. ;D
|
|
|
Post by eljib on Jan 16, 2006 20:07:50 GMT -5
JohnH: Yes, the bypass works. And the numbers for the tests you suggest are:
Without jacks plugged in: Infinite resistance @ R x 10,000 - both switch positions
With jacks plugged in: 1 ohm @ R x 100 - both switch positions
Also, I wired in the LED today (I left it out before because I didn't have the 8k2 resistor) As expected, it lights up when the switch is thrown while the input jack is plugged in. Still no compressed signal, but there is signal (loud hum).
|
|
|
Post by eljib on Jan 17, 2006 0:34:09 GMT -5
Okay, I got it working. I don't know what happened between "broken" and "awesome" but it's great now. Thanks for all your help, you two. I learned a lot.
|
|
|
Post by JohnH on Jan 17, 2006 1:27:31 GMT -5
Hey well done! And I am relieved. cos I was not sure what the next bit of sensible advice was going to be! At the end of the day, the guy building a device has to get it going. Personally, nothing I have ever built has ever worked right first time.
John
|
|
|
Post by UnklMickey on Jan 17, 2006 11:56:48 GMT -5
...I think most electronic stuff goes "open" when it fries, but I could be mistaken... too general. resistors usually open when they fry. capacitors usually "punch through" (short). coils can sometimes short between windings, but more often they open. semiconductor devices short more often than open. but none of the above are etched in stone. unk
|
|