turmoil
Active member
A friend of mine took his 5150 II to a tech within the past year to have it serviced. Apparently the tech was supposed to get a re-tube kit from euro-tubes, re-bias the amp, and that would be it. Fast forward to yesterday, my friend wanted me to look at his amp because he said it was making some humming/noises and the tech who worked on it is nowhere to be found and won't return his calls or e-mails.
He definitely got a re-tube kit for the amp, but i'm thinking he may have ordered one for the 5150, not the 5150 II. My reason for stating this is because the amp has 4 JJ 6l6GC power tubes, which is normal, but when i checked out the preamp tubes, there are 5 JJ 12AX7's (from left to right) and only 1 Electro Harmonix 12AX7 in the V6 spot, which is closest to the input jack. I know the 5150 has 5 preamp tubes, so I would guess it's possible that he got the wrong kit. Even if he did order the kit for the 5150, it shouldn't make that much of a difference as long as the power tubes are biased properly, correct?
I took the amp out of the headshell and fired it up with my weber bias rite to take some readings. The plate voltage and current seem to be normal, but there is an awful lot of noise on the lead channel when the Post control is above 2. I haven't owned a 5150 in a few years, so is this fairly normal for this amp?
Further, the one group of power tubes is reading about 5 to 6 mA less than the other set. The plate voltages, however, are about the same for both groups.
I took a recording on my cell phone, which captures the humming/noise, as well as the plate voltage and currents for both groups of power tubes. There was a delay pedal in the loop, which is that delay you hear when i switch channels, and i had a guitar plugged into the amp, which had it's volume knob turned to zero.
Assuming this level of noise is normal for the 5150 II, can anyone think of anything else that would/could be an issue?
My friend is a really nice guy and I want to be sure that everything is fine before i give it back to him so he can start ripping on it.
Thanks guys
He definitely got a re-tube kit for the amp, but i'm thinking he may have ordered one for the 5150, not the 5150 II. My reason for stating this is because the amp has 4 JJ 6l6GC power tubes, which is normal, but when i checked out the preamp tubes, there are 5 JJ 12AX7's (from left to right) and only 1 Electro Harmonix 12AX7 in the V6 spot, which is closest to the input jack. I know the 5150 has 5 preamp tubes, so I would guess it's possible that he got the wrong kit. Even if he did order the kit for the 5150, it shouldn't make that much of a difference as long as the power tubes are biased properly, correct?
I took the amp out of the headshell and fired it up with my weber bias rite to take some readings. The plate voltage and current seem to be normal, but there is an awful lot of noise on the lead channel when the Post control is above 2. I haven't owned a 5150 in a few years, so is this fairly normal for this amp?
Further, the one group of power tubes is reading about 5 to 6 mA less than the other set. The plate voltages, however, are about the same for both groups.
I took a recording on my cell phone, which captures the humming/noise, as well as the plate voltage and currents for both groups of power tubes. There was a delay pedal in the loop, which is that delay you hear when i switch channels, and i had a guitar plugged into the amp, which had it's volume knob turned to zero.
Assuming this level of noise is normal for the 5150 II, can anyone think of anything else that would/could be an issue?
My friend is a really nice guy and I want to be sure that everything is fine before i give it back to him so he can start ripping on it.
Thanks guys
