ON THE POWER TRANSFORMER OF MYFENDER TWEED AMP, WAX IS dripping on one
side. Is this normal, or has the transformer overheated and melted wax
from the laminates? I’ve included a photo of the transformer. —Lee Yue
This is perfectly normal and it is not wax. When a transformer is made, it is submerged into a vat of lacquer and a vacuum is pulled on it. This makes all the air bubbles expand and dissipate, so there is a 100 percent lacquer coating on everything inside. Then the transformer is baked in an oven to make sure the lacquer dries completely. Sometimes, the lacquer dries looking like yours. So your transformer has always looked like it does now. And just so you know, the lacquer inside the core of the transformer is there to keep all the windings stationary, even though the magnetic field is constantly changing polarity— 60 times per second in the case of a power transformer. — Gerald Weber, Kendrick Amplifiers
Will it hurt my Gibson GA-20 to use a GZ34 rectifier tube instead of the stock 5Y3? The GZ34 gets the B+ voltage up to 340 volts, which makes that amp sound better, but I’m not sure the power transformer can take it on a long-term basis. —Chad Rowe
Most vintage Gibson amplifiers need help in the gain department. Remember, they were voiced using Gibson pickups, which put out two to three times as much signal voltage as Fender pickups. And since the designers at Gibson were going for a clean sound, they would deliberately go for low gain and conservative voltages. Here is a simple test that will work with any tube amp to see if a 5Y3 can be replaced with a GZ34 or 5AR4 rectifier. Install the GZ34/5AR4, put an AC voltmeter between its pins #2 and #8, and read the voltage. If it reads 5 volts AC, the transformer likes the tube—if it is 4.1 volts AC or less, the transformer isn’t able to supply enough filament voltage to keep a GZ34 or 5AR4 happy. With your GA-20 the GZ34 will probably work fine. Here’s another little trick to bring the preamp voltages up and ultimately increase the gain of the 6SJ7 preamp tubes: Locate the 47kΩ resistor that is located between the two 10uF filter caps, and change it to a 10kΩ resistor. This mod won’t increase the preamp gain dramatically, but with a GA-20 every little bit helps.—Gerald Weber, Kendrick Amplifiers
On the Princeton Reverb amp, I would like to know which layout came first, the AB1270 or the AA1164? —David Jobin
Those numbers are codes for the month and year the amp was designed. For example, the AA1164 was designed in the 11th month of 1964. The AB1270 was designed in December of 1970. Occasionally you will see either an AA prefix in front of the code date or an AB prefix. On the first design, the prefix starts as AA, but then after some of the amps were made and one or two component values were tweaked, Fender just changed the prefix from AA to AB instead of giving the design a whole new model number. —Gerald Weber, Kendrick Amplifiers
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