Members 30secs Posted September 3, 2006 Members Share Posted September 3, 2006 My bassman is making static noise lately.. anyways, the amp has 2 power tubes and 4 preamp tubes. Are all 4 preamp tubes used when playing the guitar channel or only 2 per channel (bass/guitar) and if so which ones?Also, i replaced the pre's with 3 12ax7. are ok to use (even tho the sticker states (1x12aT7, 3x7025)? Link to comment Share on other sites More sharing options...
Members 30secs Posted September 3, 2006 Author Members Share Posted September 3, 2006 anyone? Link to comment Share on other sites More sharing options...
Members thermionic geek Posted September 3, 2006 Members Share Posted September 3, 2006 Actually there are 3 tubes used for the preamp the 4th is a phase inverter. I would suggest a 12AT7 or 12AU7 for this position because they can handle the harder work in this position a bit better. If this is an AB-165 model, and it probably is, the bias adjustment for the power tubes is not really a bias. its more of a balance control for the two tubes. this could be the source but it would be more like hum than static. My suggestion would be to swap tubes. remove the one closest to the power tubes and try another one in that position. keep moving them around and you may find you have a noisy pre amp tube. 12ax7's can be pretty inconsistant. That said as the carbon comp resistors get older on these amps they can also be noisy. These can be easily replaced. If you are a DIY type person check out Torresengineering.com they have a bunch of kits to help with these problems. you get about $2.00 worth of parts with the the $29.00 kits but they come with clear instructions that make it possible for anybody to do the work. Link to comment Share on other sites More sharing options...
Members megadan Posted September 29, 2006 Members Share Posted September 29, 2006 bump Link to comment Share on other sites More sharing options...
Members Kelly Posted September 29, 2006 Members Share Posted September 29, 2006 Static noise could be a lot of things, like dirty pots or bad switches. Take it to a tech, or messgae one the the pros here like Trace at Vooodoo Amps. Link to comment Share on other sites More sharing options...
Members JerryP Posted September 29, 2006 Members Share Posted September 29, 2006 The Fender amps usually have one tube for each channel. The fartherset two tubes to the right looking from the back are those tubes. Static noise can be caused by many things. Some of the most common causes are tubes, dirty connections, faulty plate resistors. Jerry Link to comment Share on other sites More sharing options...
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