WA9SVD
Member
Posts: 2201
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« Reply #15 on: October 28, 2007, 03:48:19 PM » |
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You definitely need a shorting stick, but it should have a (relatively) high resistance included, otherwise, shorting the HV before the bleeder has started to work can cause a large surge current and possible destroy some components. Apply the shorting stick, then leave it in place and brew a cup of coffee, or read the front section of the newspaper. Come back several minutes later. and with the shorting stick still in place, apply a jumper wire (with alligator clips on each end) between the HV and ground. Only then can you remove the shorting stick. Next, use a volt meter on the highest voltage scale to probe and make sure you didn't forget any areas than need to be discharged. Use additional jumpers to insure all voltages are reduced to zero. THEN do your repairs. While you have the amp shut down, subdued, and powerless (pun unintended?) to hurt you, take time to inspect (and even check) all the parts to look for unsuspected damage or deterioration. Leaking capacitors, charred resistors will need to be replaced, even if they haven't completely failed.
THEN (and this is VERY IMPORTANT) remove ALL of the shorting jumpers. (The power supply will appreciate it when you turn things back on.
The best thing is to get an experienced Amateur to guide you through the process, at least the first time. While "sending the amp back to the manufacturer" is a possibility, it's (IMHO) poor advice. We ALL had to learn, including learning about working with HV in a safe and sane manner. Follow safety suggestions and procedures, and YOU will become one of the experienced Amateurs in the future. You won't learn anything by shipping the amp off somewhere to get it repaired or retubed.
Be careful, and good luck.
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