Post by valvetronix on Sept 18, 2006 13:03:40 GMT -5
From one of my old students.
A few weeks ago my fender blues delucxe started acting funny. Basically, When you turn it on, the tubes will glow and the amp will sound fine...after about 15 minutes or so, the sound will cut off. There is no hiss or hum, and the tubes will still glow. It acts almost as if the standby switch was flipped. Sometimes the amp will go back to sounding fine again without notice. Do you have any idea whats going wrong, and where?
It may be loosing its signal at J3, the power amp in. So that the preamp signal isnt getting to the poweramp, ive seen this happen before, the jacks in the Fender bluess' were pretty cheap for the make of the amp. There also is another potential problem I can think of, here are 2- 330 Ohm (later issues had 470 ohms) 5W resistors used to drop the voltage to several points within the amp's solid state section (switching and reverb). These resistors have a problem overheating and causing the solder joints beneath them to go faulty.
I cant find the email, but my friend asked me about modding his Bassman so that the guitar out from the 2nd tube stage runs into the bass input, when he did this he got a weird ringing modu sound...
If anyone has, or is going to try to do this... you HAVE to replace the single 820 ohm resistor with two 1k5 resistors to keep those preamp tubes at the proper bias, and seperate the common cathodes.
A few weeks ago my fender blues delucxe started acting funny. Basically, When you turn it on, the tubes will glow and the amp will sound fine...after about 15 minutes or so, the sound will cut off. There is no hiss or hum, and the tubes will still glow. It acts almost as if the standby switch was flipped. Sometimes the amp will go back to sounding fine again without notice. Do you have any idea whats going wrong, and where?
It may be loosing its signal at J3, the power amp in. So that the preamp signal isnt getting to the poweramp, ive seen this happen before, the jacks in the Fender bluess' were pretty cheap for the make of the amp. There also is another potential problem I can think of, here are 2- 330 Ohm (later issues had 470 ohms) 5W resistors used to drop the voltage to several points within the amp's solid state section (switching and reverb). These resistors have a problem overheating and causing the solder joints beneath them to go faulty.
I cant find the email, but my friend asked me about modding his Bassman so that the guitar out from the 2nd tube stage runs into the bass input, when he did this he got a weird ringing modu sound...
If anyone has, or is going to try to do this... you HAVE to replace the single 820 ohm resistor with two 1k5 resistors to keep those preamp tubes at the proper bias, and seperate the common cathodes.