Members onelife Posted April 7, 2012 Members Share Posted April 7, 2012 Whenever someone posts a question here about their tube amp issues, the advice is always to make sure the filter caps are discharged before working on the amp. This is very good advice but none of the posts I have seen elaborate on how to do this. My suggestion is to use a clip lead and - with the amplifier disconnected from the power source - connect pin 1 of the first tube (usually labeled V1) to ground. This will gently discharge all of the filters through a few resistors to ground and will avoid the snap normally associated grounding the filter cap directly. I use this method on Fender amps and I know that it works. I think it will work on other brands of tube amps but I would suggest a look at the schematic in those cases to determine if there are any reasons why it would not. What are some of the methods that others choose to use? Link to comment Share on other sites More sharing options...
Members Brown, Charlie Posted April 7, 2012 Members Share Posted April 7, 2012 Leave it unplugged with the standby switch on / power switch off overnight, leave it that way until the chassis is back in. Probably still wise to manually drain them anyway, but this way there should already be no voltage in the amp just in case you touch something sliding the chassis out. Link to comment Share on other sites More sharing options...
Members onelife Posted April 7, 2012 Author Members Share Posted April 7, 2012 Does that mean the caps discharge back through the power transformer? Link to comment Share on other sites More sharing options...
Members fretless Posted April 7, 2012 Members Share Posted April 7, 2012 snuffer stickhttps://amptechtools.powweb.com/stick.htm Link to comment Share on other sites More sharing options...
Members onelife Posted April 7, 2012 Author Members Share Posted April 7, 2012 That looks good. Link to comment Share on other sites More sharing options...
Members Brown, Charlie Posted April 7, 2012 Members Share Posted April 7, 2012 Does that mean the caps discharge back through the power transformer? Don't know the deets, I heard thats how old school amp techs at fender did it when amps came in for service back in the day... but they only did it for maybe 30 mins or so. Me, I'm not in a hurry. Link to comment Share on other sites More sharing options...
Members wagdog Posted April 7, 2012 Members Share Posted April 7, 2012 Leaving an amp unplugged with the standby and/or power switch on DOES NOT discharge your filter capacitors. Link to comment Share on other sites More sharing options...
Members cheezit66 Posted April 7, 2012 Members Share Posted April 7, 2012 Leaving an amp unplugged with the standby and/or power switch on DOES NOT discharge your filter capacitors. Any method that doesn't finish with using a multimeter to check the voltage at the filter caps is unsafe. Leaving it overnight MIGHT work. Doing the hula while you wave a palm frond on your amp for 30 minutes might work too. Whatever you do, check that voltage!!!! I use a homegrown snuffer that involves attaching a 50k-100k 2w resistor to ground with VMM clipped across it to the B+ and it usually takes less than 2 minutes, and the resistor doesn't get hot. (If that sentence didn't make sense to you, take it to a tech!!!!). Link to comment Share on other sites More sharing options...
Members wagdog Posted April 7, 2012 Members Share Posted April 7, 2012 (If that sentence didn't make sense to you, take it to a tech!!!!). This. I see soooo many people post half-*ss methods of discharging caps and working on an amp that I usually just avoid adding to the din. My advice is to learn how to do this, safely, from someone IN PERSON and not from the internet. Link to comment Share on other sites More sharing options...
Members wagdog Posted April 7, 2012 Members Share Posted April 7, 2012 btw, onelife; your method could work... but what if the plate resistor on that preamp tube is burned in two? Link to comment Share on other sites More sharing options...
Members nicholai Posted April 7, 2012 Members Share Posted April 7, 2012 I wish I could find someone decent around Ithaca NY to work on a Bogen I have.... Link to comment Share on other sites More sharing options...
Members Snappy Hat Posted April 7, 2012 Members Share Posted April 7, 2012 I throw mine into a salt water lake first . Link to comment Share on other sites More sharing options...
Members onelife Posted April 7, 2012 Author Members Share Posted April 7, 2012 btw, onelife; your method could work... but what if the plate resistor on that preamp tube is burned in two? If the resistor was broken, that may be obvious but if it is just open then that is where the multimeter comes in (as cheezit66 pointed out above) which I thought would be a given in this situation. If the potential is still there then clip pin1 of V2 to ground. Link to comment Share on other sites More sharing options...
Members Wyatt Posted April 8, 2012 Members Share Posted April 8, 2012 Any method that doesn't finish with using a multimeter to check the voltage at the filter caps is unsafe. Leaving it overnight MIGHT work. Doing the hula while you wave a palm frond on your amp for 30 minutes might work too. Whatever you do, check that voltage!!!!I use a homegrown snuffer that involves attaching a 50k-100k 2w resistor to ground with VMM clipped across it to the B+ and it usually takes less than 2 minutes, and the resistor doesn't get hot. (If that sentence didn't make sense to you, take it to a tech!!!!). I lost three fingerprints to an amp that hadn't been powered on in nearly a year before. It took months to regrow them. Link to comment Share on other sites More sharing options...
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