Re: Help! Repair Shop ideas or amp suggestions ...

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4/12/2005 7:31 PM

Thorny

Re: Help! Repair Shop ideas or amp suggestions ... If we know where you are maybe I might know someone in the area if you don't want to ship it. You can find a listing of a people on webers web site, and also on the AGA website     http://aga.rru.com/   look under AGA Businesses     The chopstick idea is a good one, as is checking grounds. You might have a broken or nearly broken wire or more common a bad or cold solder joint. Does it only do it after it has been heated up or only when it is cold? Some folks use a heat gun or cold spray to identify items as well.     Or take it to a tech. Make them scratch their head! Good luck!     Thorny

 

4/12/2005 8:51 PM
Dale	Thanks folks. I will pull the chas. I expect I will send it to Bruce. I will look quick whne I get the chas out and see if I cna see anything.     What is the chopstick idea?     I am in SE South Dakota.     Dale

 

4/13/2005 6:35 AM

tubenit

There is high voltage in a tube amp in the filter caps that is stored that can discharge and KILL you! You're looking at often 300-400 volts plus.   These caps can discharge even when the amp has been turned off for quite some time. The volts can rupture the capillaries etc around your heart and you die (as I've been informed). To work on amps, you need to know how to safely discharge filter caps.     The chopstick idea is to have the chassis opened up and the amp hooked to a speaker and have the amp turned on. The chopstick being bamboo or plastic is non-conductive. You take the chopstick and tap on various caps and resistors to see if it makes more noise or makes the noise go away. This can sometimes help isolate the problem to a cap, resistor or solder joint.     Having said that, if you are not familiar with working on tube amps.......... PLEASE send it to a amptech. The dollars to get it up and running are much cheaper than the risk of electrocution.

 

4/13/2005 6:53 AM
Dale	I agree. I will be packing it up soon! Thanks.

 

4/13/2005 7:33 AM

Dale

Draining filter caps .... OK? It is my understanding (from reading) that this is a workable way to drain off most of the filter caps (from the Hoffman site) ...       "The easiest way to drain your filter caps is to warm up the amp and then play the amp. Do not shut the amp off with the power switch or the standby switch. Just unplug the amp from the wall and keep strumming your guitar until the sound dies away.   The voltage in the filter caps is now below a level that can hurt you. There will still be a small voltage present in the caps but it is not enough to give you a nasty shock. Typically less than 20 volts is in the cap after draining it this way."     Dale

 

4/13/2005 7:56 AM

KDakaWalt

Dale - Yes that is correct. That is the way I drain them. You can also connect a bleeder resistor to the first preamp tube to be sure that the caps don't "recover" any voltage. I do this also, but you have to remember to remove it before powering up. It is a 1K-ohm/5 watt attached to clip leads.     Whatever you do to drain them, you should always check them before you get in there.     To "chopstick" the amp it has to be on. This means you are exposed to potentially lethal voltages. I like to do this while someone is playing a guitar through the amp.     High voltage is best probed by clipping the common of the meter to a secure ground point on the chassis and using one hand with the other probe. Hold the unused hand behind your back. This way if you do catch a shock, it is less likely to pass through your heart.     Study the safety information and know the circuit before attempting this.

 

4/13/2005 1:03 PM
Dale	Other than for my knowledge I have no intention of doing the chopstick thing. I am intending to send it off to Bruce. I need an expert here, and that is not me and some stick poking around!     Dale

 

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