09-04-2015, 08:49 PM
Eric, you are confusing AC impedance with DC resistance. The PT-124 has a 7000 ohm impedance primary, but this is not what you will read with an ohmmeter. If you look at the specs, the DC resistance of the primary is only about 450 ohms ( 218 +236 ). So if you measured the existing transformer and measured 8.6K, the PT-154 would only read 450 ohms when measured the same way.
Also keep in mind that what you call the primary is really the secondary which is connected to the 71A grid. The primary was connected to the 226 plate and is the open winding.
In any case, the resistance readings and 5 watt power ratings are immaterial. What you want is a step up interstage transformer with a 1 to 3 ratio, which is the standard transformer for driving a 71A output from a 226. While the PT-154 will work with a 1 to 1.5 ratio, the PT-156 is a better choice and will provide more volume.
Also keep in mind that what you call the primary is really the secondary which is connected to the 71A grid. The primary was connected to the 226 plate and is the open winding.
In any case, the resistance readings and 5 watt power ratings are immaterial. What you want is a step up interstage transformer with a 1 to 3 ratio, which is the standard transformer for driving a 71A output from a 226. While the PT-154 will work with a 1 to 1.5 ratio, the PT-156 is a better choice and will provide more volume.
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