Haven't been able to find the answer online. The PT has a 125V and 120V primaries. Does the attached schematic show the 125V (BLUE) connected to the switch, or is the 120V (Brown) connected, or are both connected? If some one could explain the reasoning behind the 125V primary when the US power supply is 120V, it would really clear things up.
Thank you all in advance.
Dan
Schematic interpretation, PT 125V and 120V Primaries
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Schematic interpretation, PT 125V and 120V Primaries
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martin manning
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Re: Schematic interpretation, PT 125V and 120V Primaries
Average line voltage varies over the US. The spec is 114 to 126. Choose the primary lead that is closest to your average line voltage.
Re: Schematic interpretation, PT 125V and 120V Primaries
...and unless you're in a _really_ rural location, the correct answer is almost always 125.
Re: Schematic interpretation, PT 125V and 120V Primaries
Only one is to be connected. Do not connect them both. As martin and mhuss say, pick the closest to your local line voltage; and unless you know for certain that your local line voltage is centered on 120V, use 125.dpb703 wrote: ↑Mon Apr 01, 2024 12:44 pm Haven't been able to find the answer online. The PT has a 125V and 120V primaries. Does the attached schematic show the 125V (BLUE) connected to the switch, or is the 120V (Brown) connected, or are both connected? If some one could explain the reasoning behind the 125V primary when the US power supply is 120V, it would really clear things up.
Why this is true is the result of a long meandering upwards of nominal line voltage in the USA. As noted, in nearly all locations, 125vac is where the line sits today.
This increase of true line voltage can cause issues with older amps which were sold in the 50s and 60s with power transformers actually designed for 110Vac.
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Stevem
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Re: Schematic interpretation, PT 125V and 120V Primaries
What is up with that rectifier tube used in that schematic?
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Schematic interpretation, PT 125V and 120V Primaries
The experts may weigh in, but is there anything wrong with putting the 120 and 125 on a switch for a built-in "Brown Box" option on the back panel? It would equate to a 4% B+ boost or cut depending on the actual line voltage.
Just plug it in, man.
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martin manning
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Re: Schematic interpretation, PT 125V and 120V Primaries
That would be fine if the high voltage setting doesn't push the heaters over 6.3 +10%, or 6.9, which will shorten tube life. Longer life will result from keeping them closer to 6.3 or even a bit under.
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martin manning
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Re: Schematic interpretation, PT 125V and 120V Primaries
That could be any of the common rectifiers shown in the schematic snip, where pins 6 and 4 are the anodes.