Re: 200B 5 PA head hum/hiss issue [message #28171 is a reply to message #28094] |
Fri, 09 April 2021 20:54 |
Drjones1106
Messages: 19 Registered: March 2017 Location: Seattle
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A lower wattage fuse is a good call. I should have been plugged into my light bulb current limiter but like a dumbass I was plugged into the wall.
All the transistors test out fine. I took q1-4, q704/5, q708/9 and tested them all on my transistor tester. they all registered as working. though my last question about relative hFE values still stands. I get volume out of the amp. I tried a guitar and its pretty loud. I couldn't do a full vol test, so I set up a load test (same as last time) to get a voltage reading, and got some strange results. It peaks around 10v ac at around 11 o'clock volume, but then drops to around 3v after 12 o'clock. at full clockwise it comes back up to around 7v.
I didn't hook up the oscope, so I'll do that later and get some more qualitative info.
At least it powers up and isn't blowing fuses. still has a wicked noise floor. I'll also be doing more work on that front. I intend to disconnect all but one preamp, and bypass the reverb board, straight to the poweramp to see what kind of noise is there.
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