Hi Everyone, Sorry to be posting a question as soon as joining up. Iv just found this forum, I was a member on the Music Radar forum before it went down & Iv been a bit lost without it tbh. My name is Scott & I live in Pershore, Worcs. Anyway back on topic. I have a Marshall JCM 800 2204. I have just treated it to some NOS Mullard ECC83 and a matched pair of Winged C EL34. I have a problem getting the Bias current low enough on the EL34s. I have measured Plate Voltage at 435v measuring at pin 3 and ground but I cant get the bias current below about 55mA with the pot wound right down as far as it will go. My calcs are (25x0.7/435=0.040) are my calcs right? If so a tad too hot. Also Im getting a variation of 5mA between tubes. Does the amp need looking at (maybe a resistor value has wandered) or could it be the tubes. Im wondering if its time for a good service on the old beast. In the mean time should I get in touch with the seller of the EL34s or just take the amp in. I thought about contacting the seller to see if he has a cooler pair, would that fix it, Thanks in advance Scott
Comments
"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
Actually I would just change them. This is the single most common problem I find on these amps, it's more of a surprise if they *aren't* leaking.
"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
Bandcamp
Spotify, Apple et al
"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