(Reposting here as I suspect it will get seen by the right folks...)
I've got an original Elekit TU-8200 that I built back in 2016. It's developed a hum in the left channel, audible in the speaker as well as headphones. No change in volume based on volume control.
I've swapped all of the pre-amp and power tubes to no effect. Googling led me here and suggests I need to replace my FET(s).
I've measured the voltages at the documented test points, and several on the left channel are out of spec. Anything else I should check, or just order some FETs and swap them out?
Thanks!
Voltages (with 12AU7 and 6L6EH installed):
1 -> 3.8
2 -> 3.5
3 -> 3.6
4 -> 3.6
5 -> 123
6 -> 119
7 -> 127.1
8 -> 116.1
9 -> 220.2
10 -> 208.9
11 -> 1.1
12 -> 0.58
13 -> -20
14 -> -17.3
15 -> 0.03
16 -> 0
17 -> 0.46
18 -> 0.43
19 -> 285.8
20 -> 271.5
21 -> 285.4
22 -> 318.3
23 -> 291.3
24 -> 279.8
25 -> 287.4
26 -> -33.2
27 -> -34.5
28 -> 5.9
29 -> 6.2
Tangentially, and assuming I have to pull the board and solder on new FETs or other components, any must-have mods I should consider including? I built it stock 8 years ago, and was very happy with it new, but I also don't know what I may be missing.
Thanks all!
I've got an original Elekit TU-8200 that I built back in 2016. It's developed a hum in the left channel, audible in the speaker as well as headphones. No change in volume based on volume control.
I've swapped all of the pre-amp and power tubes to no effect. Googling led me here and suggests I need to replace my FET(s).
I've measured the voltages at the documented test points, and several on the left channel are out of spec. Anything else I should check, or just order some FETs and swap them out?
Thanks!
Voltages (with 12AU7 and 6L6EH installed):
1 -> 3.8
2 -> 3.5
3 -> 3.6
4 -> 3.6
5 -> 123
6 -> 119
7 -> 127.1
8 -> 116.1
9 -> 220.2
10 -> 208.9
11 -> 1.1
12 -> 0.58
13 -> -20
14 -> -17.3
15 -> 0.03
16 -> 0
17 -> 0.46
18 -> 0.43
19 -> 285.8
20 -> 271.5
21 -> 285.4
22 -> 318.3
23 -> 291.3
24 -> 279.8
25 -> 287.4
26 -> -33.2
27 -> -34.5
28 -> 5.9
29 -> 6.2
Tangentially, and assuming I have to pull the board and solder on new FETs or other components, any must-have mods I should consider including? I built it stock 8 years ago, and was very happy with it new, but I also don't know what I may be missing.
Thanks all!
A New FET will solve the issue. You need to replace the original 6L6GC
There are sevesal options to upgrade the amp
1. Coupling cap -- Mundorf EVO si;ver Gold
2. LundaHL ll2777b
3. Alps r27
There are sevesal options to upgrade the amp
1. Coupling cap -- Mundorf EVO si;ver Gold
2. LundaHL ll2777b
3. Alps r27
Just to follow up, Viktor was correct and new FETs solved my hum. I was able to confirm that one was indeed blown after I pulled them out. In case it helps anyone else, I went with Toshiba's TK3A65D as it seemed awfully closely spec'd.