Tweet
I Just got this 3 channel mesa dual rectifier on the bench and darn do i love following the signal through all of those relays on the board!!!! Cough..
Well i started going through to see where the signal stopped and i think that the muting circuit is telling it to mute. because it looks like that’s where the signal gets grounded out on the center leg of the master pot right where it goes into one of the three muteing transistors. It looks nice and clean and strong before then on the first channel.
I tried removing those muting transistors (one of which was tied to the center leg of the master pot of ch. 1) to see if it let the sound thru again and what i noticed was it started drawing twice as much current roughly through the variac a nice normal amount current draw but still no output like i would except when it started drawing more current.
Does removing those transistors allow the signal to go thru unmuted or no?
I checked all the normal things before i removed the muting transistors like power rails, the tubes, visual inspections, bad connections, and so on. I am getting a pre amp signal but nothing is going to the power section. I'm seeing the pulses on the mute pulse pin when i do the channel select and i checked the voltages and they matched what was on the schematic for the muting circuitry and all the diodes and transistors i believe, unless it’s like an intermittent or leaky transistor or something that i cant test with a diode tester. My next attempt may be just to change out the lm3914 i.c. but im thinking since im seeing the pulse at least that its working unless im mistaken.
Any ideas as to what could be the trouble what i should do and if im incorrectly trying to disconnect the muting circuitry, thanks for the help.
Well i started going through to see where the signal stopped and i think that the muting circuit is telling it to mute. because it looks like that’s where the signal gets grounded out on the center leg of the master pot right where it goes into one of the three muteing transistors. It looks nice and clean and strong before then on the first channel.
I tried removing those muting transistors (one of which was tied to the center leg of the master pot of ch. 1) to see if it let the sound thru again and what i noticed was it started drawing twice as much current roughly through the variac a nice normal amount current draw but still no output like i would except when it started drawing more current.
Does removing those transistors allow the signal to go thru unmuted or no?
I checked all the normal things before i removed the muting transistors like power rails, the tubes, visual inspections, bad connections, and so on. I am getting a pre amp signal but nothing is going to the power section. I'm seeing the pulses on the mute pulse pin when i do the channel select and i checked the voltages and they matched what was on the schematic for the muting circuitry and all the diodes and transistors i believe, unless it’s like an intermittent or leaky transistor or something that i cant test with a diode tester. My next attempt may be just to change out the lm3914 i.c. but im thinking since im seeing the pulse at least that its working unless im mistaken.
Any ideas as to what could be the trouble what i should do and if im incorrectly trying to disconnect the muting circuitry, thanks for the help.
Comment