Hi everybody,
i start a new thread here which is a kind of a continuity with the previous one that was title "troubleshooting a M40 with loud hum"(for beginers)
- thanks to members of this site i managed to remove this hum, it seems that it was due to faulty caps causing a DC leakage (and especially the 0.1uf like C23.)
-All the electrolytic caps are new exept the four 2nf caps behind the front pannel hooked to the input vol pots.
- Now the amp is working and have a descent sound, but there is this noise, white noise/parasitic oscillation that i can control with the main volume "lautstärke"
it's very loud, i can also control the tone of this noise with the trebble&bass pots..
it kind of sounds like a vintage radio when you're searching stations..
- Do somebody have some tips to get rid of this parasitic oscilliation noise?
- i checked the value of a lot of resistor in it and they seem ok
i already changed the 20k plate load resistor of Rö1&2
-i hope it is "just" a loud parasitic noise that's not gonna damage the amp..
- i soldered the 1Meg resistor between the ground & the tip, on the input jack, it has reduced the noise a bit
but i have lost the crunch..
in the attached pics this my work so far ( it's not neat, the filtering caps are temporary set)
cheers Nick
i start a new thread here which is a kind of a continuity with the previous one that was title "troubleshooting a M40 with loud hum"(for beginers)
- thanks to members of this site i managed to remove this hum, it seems that it was due to faulty caps causing a DC leakage (and especially the 0.1uf like C23.)
-All the electrolytic caps are new exept the four 2nf caps behind the front pannel hooked to the input vol pots.
- Now the amp is working and have a descent sound, but there is this noise, white noise/parasitic oscillation that i can control with the main volume "lautstärke"
it's very loud, i can also control the tone of this noise with the trebble&bass pots..
it kind of sounds like a vintage radio when you're searching stations..
- Do somebody have some tips to get rid of this parasitic oscilliation noise?
- i checked the value of a lot of resistor in it and they seem ok
i already changed the 20k plate load resistor of Rö1&2
-i hope it is "just" a loud parasitic noise that's not gonna damage the amp..
- i soldered the 1Meg resistor between the ground & the tip, on the input jack, it has reduced the noise a bit
but i have lost the crunch..
in the attached pics this my work so far ( it's not neat, the filtering caps are temporary set)
cheers Nick
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