Members jazzbo Posted August 30, 2005 Members Share Posted August 30, 2005 Is there a web site that shows how to do this? I have basic breadboard electronics experience but I never worked on a high-voltage amp before. Would I be crazy to try without experience? I'd like to learn how to work on amps but I don't know where to start. Link to comment Share on other sites More sharing options...
Members GITTarzann Posted August 30, 2005 Members Share Posted August 30, 2005 Don't be Skeered Link to comment Share on other sites More sharing options...
Members zac102 Posted August 30, 2005 Members Share Posted August 30, 2005 just use something to short the two leads on each of the capacitors, preferably not your fingers. I like to just stick a screwdriver across them. Link to comment Share on other sites More sharing options...
Members GITTarzann Posted August 30, 2005 Members Share Posted August 30, 2005 I read a bit about discharging caps in the infamous Dan Torres book..Inside Tube Amps, but there isn't much too it. I don't remember for sure so I will not quote, but it is just a resistor and an alligator clip and a probe of some sort. I know a lot of the more modern amps will discharge them selves if shut off for a little while. but about the don't be Skeeeeered commment....you shouldn't be....just be respectful, which it sounds like you are since you are asking. Link to comment Share on other sites More sharing options...
Members Deuterium Posted August 30, 2005 Members Share Posted August 30, 2005 Keep one hand in your pocket AT ALL Times. The other hand hold the insulated handle of a screwdriver, and make a connection with screwdriver shaft by touching across the capacitor to chassis (ground). Do NOT be touching the chassis with any part of your body. Also...Wait at least 4-5 hours after totally powering off the amp before even trying to discharge the capacitors!!!!! Link to comment Share on other sites More sharing options...
Members Fred5 Posted August 30, 2005 Members Share Posted August 30, 2005 Just google it, dude. Also, it IS dangerous - you can get killed, the high voltage stored in the capacitors can stop your heart, blow the cap up in your face or melt your screwdriver. Whether you're "respectful" or not has nothing to do with it. Link to comment Share on other sites More sharing options...
Members jazzbo Posted August 30, 2005 Author Members Share Posted August 30, 2005 All right guys, thanks. I pulled the chassis out of the amp and I am still here. The reason I did this was to check "internal fuses" for the tubes... according to an earlier post this amp should have them. I'm not exactly sure what I should be looking for. It looks like there is something that might be a fuse soldered to the board for each pair of 6l6's. Wiry thing with a lump in the middle. Does this sound right? Link to comment Share on other sites More sharing options...
Members Deuterium Posted August 30, 2005 Members Share Posted August 30, 2005 Originally posted by Fred5 Just google it, dude. Also, it IS dangerous - you can get killed, the high voltage stored in the capacitors can stop your heart, blow the cap up in your face or melt your screwdriver. Whether you're "respectful" or not has nothing to do with it. ***************************** Also wise words. I would do as Fred advised, and do a bit more research on the www. Link to comment Share on other sites More sharing options...
Members GITTarzann Posted August 30, 2005 Members Share Posted August 30, 2005 Originally posted by Fred5 Whether you're "respectful" or not has nothing to do with it. That is a bunch of BS.. Respecting what you are working with has everything to do with it. You are potentially discharging 300- 600 volts DC. Respect it, but don't be afraid of it. Know how to do it, and do it the way it should be done and it is a piece of cake. Link to comment Share on other sites More sharing options...
Members jazzbo Posted August 30, 2005 Author Members Share Posted August 30, 2005 Well, don't worry, I'm not gonna mess with it... I just wanted to make sure it was safe to remove my chassis to check if the internal fuses for the tubes has blown. I'm not touching anything, just looking. I think I see the fuses - can someone confirm for me that they are just wires soldered to the tube board, with big lumps in the middle? One for each pair of 6l6's. Link to comment Share on other sites More sharing options...
Members GITTarzann Posted August 30, 2005 Members Share Posted August 30, 2005 Just do some research...KNOW what it is you want to discharge... Aquire the right materials to do it.....and it really is easy......if you don't feel comfortable don't do it, but it really is simple..just do the research. Link to comment Share on other sites More sharing options...
Members jazzbo Posted August 30, 2005 Author Members Share Posted August 30, 2005 Originally posted by GITTarzann Just do some research...KNOW what it is you want to discharge...Aquire the right materials to do it.....and it really is easy......if you don't feel comfortable don't do it, but it really is simple..just do the research. Right, I'm not worried about the caps anymore, just wanted to check the fuses. Link to comment Share on other sites More sharing options...
Members rastaman Posted August 30, 2005 Members Share Posted August 30, 2005 As far as I know, ALL fuses should be accessable from the OUTSIDE of the amp. At least the ones the general public should be concerned with. Link to comment Share on other sites More sharing options...
Members Fred5 Posted August 30, 2005 Members Share Posted August 30, 2005 ^ Typical user serviceable fuse. ^ typical guitar amp cap. they can be different sizes, like about half a finger or finger or bigger. Link to comment Share on other sites More sharing options...
Members jazzbo Posted August 30, 2005 Author Members Share Posted August 30, 2005 Originally posted by Fred5 ^ Typical user serviceable fuse. ^ typical guitar amp cap. they can be different sizes, like about half a finger or finger or bigger. Thanks. I already put the chassis back in the cabinet. I couldn't see any broken connections anywhere and I'm not going to mess around with it further than that. Yeah, I know what a cap and a fuse look like but I didn't see anything inside that looked like a fuse, except for something that looked like one of those old wire fuses. Anyway it wasn't broken so I guess the problem is not a fuse. Link to comment Share on other sites More sharing options...
Members scottosan Posted August 30, 2005 Members Share Posted August 30, 2005 Originally posted by GITTarzann That is a bunch of BS..Respecting what you are working with has everything to do with it.You are potentially discharging 300- 600 volts DC.Respect it, but don't be afraid of it. Know how to do it, and do it the way it should be done and it is a piece of cake. shorting it out with a screwdriver is dangerous. Clay Finlyey had the tip of his screwdriver chip off on took flight. Go sped 3 bucks on a resistor wire and allegator clip Link to comment Share on other sites More sharing options...
Members kannibul Posted August 30, 2005 Members Share Posted August 30, 2005 Do this first. Take your meter, set it to voltage. Stick one lead on a ground connection for the amp. take the other lead, and touch it to both ends of the cap. Make sure it reads 0 volts on both ends. Some caps are put in backwards - like in the bias section, where your voltage is actually negative in respect to ground, so your positive terminal is actually your ground... If you read a voltage, then worry about draining the caps. Most of the amps I have come across, have some kind of bleeding circuit - though, I have not opened up many amps to be honest. Link to comment Share on other sites More sharing options...
Members rgt320 Posted August 30, 2005 Members Share Posted August 30, 2005 Originally posted by Fred5 Just google it, dude. Also, it IS dangerous - you can get killed, the high voltage stored in the capacitors can stop your heart, blow the cap up in your face or melt your screwdriver.Whether you're "respectful" or not has nothing to do with it. +1 Link to comment Share on other sites More sharing options...
Members Stratotone Posted August 30, 2005 Members Share Posted August 30, 2005 Originally posted by rastaman As far as I know, ALL fuses should be accessable from the OUTSIDE of the amp. At least the ones the general public should be concerned with. I had a peavey 60/60 power amp, it had internal fuses. Pete Link to comment Share on other sites More sharing options...
Members Stratotone Posted August 30, 2005 Members Share Posted August 30, 2005 Here's what I do... and if you zap yourself, it isn't my fault. I turn the amp on and the standby in the 'play' position - just like I would if I was going to play guitar. this seems to drain every amp I've come across. Let it sit like that for a minute or so. Then I measure the caps with a multimeter to see if they are storing any change. If they are then I go ahead and discharge it with a wire that has a 1 watt resistor in between - can't remember what size, but it works ok. Never had anything blow up doing it that way, but I have heard of guys getting pieces of screwdriver flying all about. You'd be surprised how violent an amp discharging 400 plus volts can be. Sometimes the caps will 'bounce back' and build up a charge again. I usually alligator clip a wire to a ground point and then to the caps to keep them from charging back up. I'm a careful guy (used to repair monitors, where they store as much sometimes more voltage than guitar amps) and I still have been zapped a few times. It isn't fun. Pete Link to comment Share on other sites More sharing options...
Members GITTarzann Posted August 30, 2005 Members Share Posted August 30, 2005 Originally posted by Stratotone Here's what I do... and if you zap yourself, it isn't my fault.I turn the amp on and the standby in the 'play' position - just like I would if I was going to play guitar. this seems to drain every amp I've come across. Let it sit like that for a minute or so. Pete That is what I do too, you just need to make sure you have the amp unplugged when you do this... Link to comment Share on other sites More sharing options...
Members LPBlue Posted August 30, 2005 Members Share Posted August 30, 2005 The resistor/wire method works fine but the resistor is not really needed. I use a wire with alligator clips hooking one end to the chassis and the other end to the plate of V1.The caps will drain quickly and safely through the plate resistors. I usually monitor the voltage drop as well just to be safe. When the caps are drained, leave the wire in place until you are finished working otherwise the caps may "re-group" their residual charge. My .02Cdn. Link to comment Share on other sites More sharing options...
Members Stratotone Posted August 30, 2005 Members Share Posted August 30, 2005 Originally posted by GITTarzann That is what I do too, you just need to make sure you have the amp unplugged when you do this... If they don't realize that, they deserve to be shocked... Pete Link to comment Share on other sites More sharing options...
Members GITTarzann Posted August 30, 2005 Members Share Posted August 30, 2005 lol.......I guess so. Link to comment Share on other sites More sharing options...
Members rastaman Posted August 30, 2005 Members Share Posted August 30, 2005 My amp tech and myself also use a 100ohm resistor w/ soldered jumper clips and shrink wrap on it to discharge. There may be better/easier ways but this works fine. Link to comment Share on other sites More sharing options...
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