Copper Talk » Ask The Tech » Amplifiers » D&A PHANTOM DUAL POWER AMP "BLOWING A/C FUSE " « Previous Next »

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Tigergriz
New member
Username: Tigergriz

Post Number: 6
Registered: 11-2020
Posted on Wednesday, May 11, 2022 - 2:26 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Hi guys, /gals, I appreciate any help in advance, I am good with a soldering iron and with google and I would take this amp to a certified repair guy , but the one in my area is so busy he does not reply, so all I am asking is where to start to check the circuit for trouble, history, the amp was running fine, a little low on power so I bought all nos tested 100% 6LQ6 Tubes, installed them and sizzle pop blew main power A/C fuse, so I removed all tubes, looked for damage bulging caps, burnt diodes ETC. could not find visual damage, so in goes new 30 amp A/C fuse all tubes still removed, and when powered on pop goes the fuse, so now I have checked the actual power switch to see if it went to ground when flipped on and no, nor do the wires down stream as far as I could understand how to trace, the amp does have several shady areas I could see, like wires going through a hole under the transformers with no protection, or restraint but it is so tight under transformers I cant see if any wires are making contact through frayed insulation, it appears not, I have a couple good multi meters, but I am not a tech so any next steps from a person of experience would be greatly appreciated,
I take a lot of pictures as my eyes are not what they used to be, helps me magnify things, hoping it helps, oops also the ending 3343 jpeg pic of 2 watt what. diodes for the rectifiers circuit is my work, one blew up, causing the charred red wires behind them, the amp worked fine after the diode replacement
Ken
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Tech833
Moderator
Username: Tech833

Post Number: 2512
Registered: 8-2002
Posted on Monday, December 05, 2022 - 1:50 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Poor man's way-

Check to see where the short is by putting multimeter set to "ohms" on the power leads (with a new fuse in the power leads of course). Now, assume your ohm meter is reading a short, yes? OK, now, begin disconnecting power components one leg at a time until the ohm reading suddenly jumps way up. There's your bad component.
Your radio 'Mythbuster' with Copper Electronics since 1998

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