Some basic help needed.
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| Posted on April 17, 2014 at 23:11:30 | ||
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Posts: 29
Location: bay area california Joined: October 3, 2004 |
Hello, i have a vtl st-150 circa 2002. It blew a 1k ohm resistor and the channel b+ fuse blew due to a bad tube which i didn't know at the time. i replaced the resistor and fuse and checked the bias. the bias voltage exceeded the nominal 280 mv expected to a point it saturated my measurement setting. all other tubes in the channel checked out with expected bias value. so i swapped a good tube into the bad position and the bias started to run away and eventually the b+ fuse blew. i checked on the resistor that i replaced along with the others and they measured as expected. i ohm out left vs right channel without power and couldn't find any differences in the various power resistors. power diodes are ok. without a schematic for test points to diagnose, what can i do to further debug this myself? is it possible that i have a bad bias trim pot as well? what would cause the b+ fuse to blow when a good tube is placed in the bad position? the bad tube does not cause the b+ fuse to blow but the bias reading was out of range. any advice and thought to how to proceed. thanks in advanced. viet
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