Iv got the chance to pick up a nice 1981 Marshall JMP 2204 (one of the last ones) Iv asked for photos of the chassis, it all looks very nice and untouched, however I have noticed that there are no 1k 5w resistors over pins 4 & 6 of the EL34 valve bases, I have seen this before but would it have left Marshall factory like that? Is there risk of damage upstream if a valve goes bad without them. Also the bias caps look the wrong voltage to me. They are 10uf 100v but saying that they also look original. Other than that it looks a great amp and If it ticks the box when I try it out tomorrow, i will deffo buy it. Cheers in advance
Comments
The bias caps are correct, but make sure they haven't started to leak - if you can't get the bias voltage up high enough to go slightly too cold then they need replacing. This is more common than the main caps failing, in fact.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Try squeezing the terminal rivet hard onto the track board with a pair of fine-nose pliers and see if the reading goes down to 1M.
If it does, try it back in the amp - and also bridge the rotor to the CW terminal, which will stop the pot going open circuit if it's actually a rotor contact problem - this is good practice with any pot used as a variable resistor.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein