Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: imgumby001 on December 03, 2020, 10:54:35 pm
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Hello everybody!! Just completed my first “from scratch” build, and I’m having an issue with V1. I’m getting no signal out of it as far as I can tell. My question is, on v1, pin 1 there’s no voltage. Coming out of my .22uf cap is a 220k resistor. I’ve got 274.7vdc on the upstream side, but I’m reading nada on the other. In the same position on v2 I have 294.5vdc on the upstream side of the 220k, and a solid 160.6 on pin1. I pulled the 220k resistor off pin 1 of v1 and ohmed it out, as I did before I installed it, and it read good on resistance. Reinstalled it and got the same readings. Is it safe to say this resistor is bad? I don’t have another 220k here at the house to swap it with, so I can’t just do that currently. Am I on the right track?
Thx!!
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Do you know if the tube is good?
If the resistor reads the proper resistance, it's probably good.
Another thing to check is your cathode resistor and the connection to ground from that resistor. If you have a bad connection either from the cathode to the resistor, or the resistor to ground, you won't get any current flow. But then, the voltage would probably be the same on both sides of the plate resistor, so that makes me wonder about the possibility of a short in the tube...
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I swapped the tube from v2 and back, and checked a different set of brand new shugang’s. All came out the same. In the morning I’m going to recheck every wire and connection for continuity and grounding. It’s got me...
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Measure resistance from pin 1 to ground.
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I got it guys. It was the shielded run from pin one. The inner shielding must have melted a bit during soldering to the turret. I had continuity between the signal turret and the ground turret. Amp sounds good. It’s rather quiet, but sounds good. Probably the ugliest thing you’ve seen in a while, but what the hey, it’s my first try at making it from a real-deal pile of parts. The next one will be better!!
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...
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And finally...
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LOL. That happens -- that's why you check for continuity after making that wire.
Your build looks great. Very tight and small. I like . . .
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It looks good to me. :smiley:
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Thanks guys!! Means a lot. I worked hard.