02-05-2010, 06:49 PM
Hi Nelson
You will find that a set's voltages, as read with any modern DMM, will read higher than what is published in old service literature. This is because in 1931 when the 90 was new, the voltage measurements were taken with meters that tended to load down the circuit under test. Now when we test those same circuits today using modern multimeters, we get higher readings than they did back then.
That having been said, are your voltage readings significantly off? Yes, you should measure your voltages using the chassis as common.
Now let's discuss the sound quality. The early 90 with push-pull 45 tubes used what is called a power detector instead of the diode second detector which came into general use later, along with automatic volume control (AVC). In your radio, that is the 24 tube just before the 27 first audio amp. One of the characteristics of the power detector is distortion. So you can't expect pure high fidelity sound from any radio with a power detector.
I don't think you should hear gargling noises, though. Maybe your voltage measurements may indicate a problem?
You will find that a set's voltages, as read with any modern DMM, will read higher than what is published in old service literature. This is because in 1931 when the 90 was new, the voltage measurements were taken with meters that tended to load down the circuit under test. Now when we test those same circuits today using modern multimeters, we get higher readings than they did back then.
That having been said, are your voltage readings significantly off? Yes, you should measure your voltages using the chassis as common.
Now let's discuss the sound quality. The early 90 with push-pull 45 tubes used what is called a power detector instead of the diode second detector which came into general use later, along with automatic volume control (AVC). In your radio, that is the 24 tube just before the 27 first audio amp. One of the characteristics of the power detector is distortion. So you can't expect pure high fidelity sound from any radio with a power detector.
I don't think you should hear gargling noises, though. Maybe your voltage measurements may indicate a problem?
--
Ron Ramirez
Ferdinand IN
