Follow It Home Posted April 9, 2008 Share Posted April 9, 2008 All right guys this is the last time ill ask this question I promise haha. When im checking the voltage before I work on my amp. 1. Take the chassis out. 2. Put the black probe of my multimeter to the ground and the red to each side of all the showing resistors. 3. The reading should be 0 (or very very close to it) Is this the right processs, I would like to start modding, but the voltage thing is frightening me. Thanks, I realize this is annoying. Link to comment Share on other sites More sharing options...
ricach Posted April 9, 2008 Share Posted April 9, 2008 Hate to say this, but you're not ready poking into high voltage yet. Resistors are not your problem, capacitors are. And only certain ones. I'm not sure what to suggest as a way to prepare yourself - you can only read so much. Do you have a friend who could help out the first time you're inside the chassis? Link to comment Share on other sites More sharing options...
TWANG Posted April 9, 2008 Share Posted April 9, 2008 you have the procedure right.. I'd add hand in pocket to keep from dieing. you have to plug the amp in, have a speaker connected, let it warm up ten minutes then take it off standby. skip any of that and you'll either fry your amp or get goofy readings. You only need to read certain points on some resistors and on the certain pins of the tubes. there should be a page in the stick faq that tells you about biasing.. and there should be a page about where to test. If you don't find that, ask again, and I'll type it out. Kinda long and I'm lazy so please look. TWANG Link to comment Share on other sites More sharing options...
tortuga Posted April 9, 2008 Share Posted April 9, 2008 He's talking about making sure the capacitors are discharged. As often as it comes up and as important as it is, it would be nice if someone made a short video clip of the procedure and posted it on you tube. If I ever get around to actually working on mine I'll try to do that (after first having some of the old pros review it to make sure I did it right). Link to comment Share on other sites More sharing options...
ricach Posted April 9, 2008 Share Posted April 9, 2008 How about making sure the meter is set to read DC voltages correctly. Make sure the probes are making good contact. That there is no 'coating' or anything else that would not allow good contact with the resistor/capacitor leads. So many things can provide a 'false' sense of security. If you're going to attempt this anyway, I suggest first doing this: With the amp off: -Buy an alligator clip for the black probe and clip this to ground. This keeps both hands from being inside the chassis. -Make sure you have good ground by setting your meter to read resistance and then (red) probe another part of the chassis and make sure you get a zero resistance reading. -Set the meter to read DC Voltage - if it doesn't autorange, then make sure it can read up to 500V Turn the amp on: -Reverify you have your meter set to read 500V DC Voltage -One hand in your pocket, (red) probe the leads of the can-like capacitors to make sure you can actually read voltages. (Only one side will show a voltage, the other side might be grounded and read zero) This tells you all contact/connections are good. Turn the amp off. Unplug the power cord: -Now probe the same capacitor leads and watch as the voltages drain down to almost zero. Have I left anything out? Link to comment Share on other sites More sharing options...
TWANG Posted April 9, 2008 Share Posted April 9, 2008 don't test current with your tongue. Link to comment Share on other sites More sharing options...
Follow It Home Posted April 9, 2008 Author Share Posted April 9, 2008 I know I need to read the caps, but I thought the cap leads were underneath the board and I couldnt reach them. Link to comment Share on other sites More sharing options...
tortuga Posted April 9, 2008 Share Posted April 9, 2008 See the following post to understand why he is asking about resistors: Link to Post Link to comment Share on other sites More sharing options...
ricach Posted April 10, 2008 Share Posted April 10, 2008 See the following post to understand why he is asking about resistors: Ah. I can see where the confusion is. That's a really confusing and scary post, lol. And considering Follow It Home is obviously very new at this, I find some of the comments very irresponsible. Although a Vjr. is pretty safe to work on, any 'safety' procedures he learns he'll be able to use and keep him safe on maybe the next tube amp he opens that is P2P and not so safe to work on. Lets help him learn the correct way now. Link to comment Share on other sites More sharing options...
Follow It Home Posted April 10, 2008 Author Share Posted April 10, 2008 All right, so I have to check the caps, I figured that but who knows. Do I have to lift up the board to do that? I was thinking about taking the chassis out of my amp and probing around with a chopstick, just cause I haven't before, would that be ok, just keeping one hand in my pocket? I really just need some straight answer you know. Stick probe here, if it reads volts, your not ok, that kind of thing. Thanks guys. Link to comment Share on other sites More sharing options...
ricach Posted April 10, 2008 Share Posted April 10, 2008 Follow It Home - Many people here have been gracious enough and taken some of their time to provide you with loads of information, some useful, some not so useful. You could extend some graciousness by taking the time to learn and understand what we are telling you. Not only would you have learned alot by now, you would have figured out the answer you're looking for all by yourself. To clear up any confusion - if the resistor is connected to the capacitor, then reading the resistor lead is the same as reading the capacitor lead. Since the resistors are above board, makes sense to take the readings from there. Link to comment Share on other sites More sharing options...
Follow It Home Posted April 10, 2008 Author Share Posted April 10, 2008 Thanks, I guess. I didn't realize I was being such a ****? Link to comment Share on other sites More sharing options...
ricach Posted April 10, 2008 Share Posted April 10, 2008 Thanks' date=' I guess. I didn't realize I was being such a ****?[/quote'] No, just too anxious for your own good. It's very difficult to write out exact step-by-step instructions and not still have them be mis-interpreted. And with high-voltage involved, that can be deadly. If you understand the concepts a little better, it will keep you from blindly following directions that could lead down a deadly path. Fortunately, the Vjrs are pretty safe to work on. It's the point-to-point wired ones that can be dangerous. But for habit sake - its always best to follow the exact same precautions no matter what amp you are working on. Link to comment Share on other sites More sharing options...
ricach Posted April 10, 2008 Share Posted April 10, 2008 Looking at the schematic R10 thru R13 and C6 thru C12 is where you will find high voltage. If you check both sides of R13 (with the red probe - black probe is grounded), that should be enough to determine if there is any voltage still remaining after turning off your amp, and unplugging the power cable. But as I suggested previously, check to see what voltage is there with the amp on first. This will make sure you've got the right connections and the meter is set correctly. You should see two different voltages on either side of R13. Link to comment Share on other sites More sharing options...
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