So a friend of mine found a couple 845's in a stash of his.
They're old (definitely used) but they look good.
They're obviously not the same, but I decided I'd try them out to see how they sound together.
So I put them in the amp, powered it up, and the first thing I noticed is that the filaments draw more current than my new production Shuguang 845B's. I'm using Rod Coleman regulators, and where I had the regulators set to 10V for the Shuguang's, these tubes were sitting around 7V. So I adjusted the trimpot until they were both reading 10V.
My B+ is 950V, and I'm cathode biasing the tubes with 1320 ohm's of resistance from cathode to ground. This should put the cathodes around 115V.
The Westinghouse labelled one biased up just like the Shuguangs, about 115V on the cathode, roughly 80mA flowing through the tube.
But the United 845W was sitting at 80V on the cathode, and 55mA flowing... This seems way off.. Is this indicative of a bad tube? Or why would this one be so far different?
Here are a couple pics of the tubes:
They're old (definitely used) but they look good.
They're obviously not the same, but I decided I'd try them out to see how they sound together.
So I put them in the amp, powered it up, and the first thing I noticed is that the filaments draw more current than my new production Shuguang 845B's. I'm using Rod Coleman regulators, and where I had the regulators set to 10V for the Shuguang's, these tubes were sitting around 7V. So I adjusted the trimpot until they were both reading 10V.
My B+ is 950V, and I'm cathode biasing the tubes with 1320 ohm's of resistance from cathode to ground. This should put the cathodes around 115V.
The Westinghouse labelled one biased up just like the Shuguangs, about 115V on the cathode, roughly 80mA flowing through the tube.
But the United 845W was sitting at 80V on the cathode, and 55mA flowing... This seems way off.. Is this indicative of a bad tube? Or why would this one be so far different?
Here are a couple pics of the tubes:
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