Superlite TMB First build
Posted: Thu 01/08/15 8:45 am
Hello.
By the end of summer i bought a homemade 18W amp. The guy who was selling it advertised it as a 18watt Marshall clone without the tremolo channel (instead there was TMB). I guess the amp was ok build because it worked. One day i started to notice that i couldnt get preamp distortion from the amp (when i cranked the preamp and left master volume kind of low it would only get pretty loud but there was little of breakup. Only when i maxed out the preamp and master it started to distort). What im trying to say is that the MV had to be cranked for preamp to work. Watching some videos on youtube from the other builders i have seen that they did not have this problem. The amp was dirt cheap (the guy sold me fully loaded chassis with cabinet and speaker with cabinet for 200$) and i was aware i would have to invest in it to sound like it should. I swapped the speaker and tubes and even though it sounded better still it felt like something was holding back the preamp volume, like it was having too much of a clean headroom and it sounded dull.
Upon further inspection into the chassis i have found a wire jungle. There was no turret board, components were hanging in air while some of them were soldered directly to tube sockets and the tube sockets looked like rotten teeth. I could not compare it to any 18w layout as the components were having some crazy values (can capacitor was 200+100+50uF)
I replaced everything except the chassis, output and power transformer and rebuild it following this layout
http://rh-tech.org/public/18-Watt/18W_S ... ut_new.jpg" onclick="window.open(this.href);return false;
I did almost everything stock with the layout except 0.01 cap before and after 33uF capacitor i have placed 0.1uF and instead of 500uF i have placed a 470uF cap (i only replaced them because that was available to me at the time).
So finally, whats the problem ?
When i powered the amp tubes light up and the status led was lit but after one second it went dead (did i mention this is my first tube amp build, and while soldering the board i have foolishly removed the resistor from the status indicator). Other than the status indicator not working the fuse did not blow and the tubes stay lit, and while there is some amount of hum coming from the speaker the sound from my guitar does not.
only when i max the preamp volume, master volume and treble some high frequencies bleed through to the speaker and fade away like tiny sounds. Sounds like there is a massive block somewhere in the circuit. There was no burning smell and no smoke when i powered the amp and as i can see the components on board look fine.
Sorry for the long writeup but as i checked everything and compared the layout of my build with the layout from this forum i really have no idea what might went wrong so any suggestion is more than welcome.
thanks in advance.
By the end of summer i bought a homemade 18W amp. The guy who was selling it advertised it as a 18watt Marshall clone without the tremolo channel (instead there was TMB). I guess the amp was ok build because it worked. One day i started to notice that i couldnt get preamp distortion from the amp (when i cranked the preamp and left master volume kind of low it would only get pretty loud but there was little of breakup. Only when i maxed out the preamp and master it started to distort). What im trying to say is that the MV had to be cranked for preamp to work. Watching some videos on youtube from the other builders i have seen that they did not have this problem. The amp was dirt cheap (the guy sold me fully loaded chassis with cabinet and speaker with cabinet for 200$) and i was aware i would have to invest in it to sound like it should. I swapped the speaker and tubes and even though it sounded better still it felt like something was holding back the preamp volume, like it was having too much of a clean headroom and it sounded dull.
Upon further inspection into the chassis i have found a wire jungle. There was no turret board, components were hanging in air while some of them were soldered directly to tube sockets and the tube sockets looked like rotten teeth. I could not compare it to any 18w layout as the components were having some crazy values (can capacitor was 200+100+50uF)
I replaced everything except the chassis, output and power transformer and rebuild it following this layout
http://rh-tech.org/public/18-Watt/18W_S ... ut_new.jpg" onclick="window.open(this.href);return false;
I did almost everything stock with the layout except 0.01 cap before and after 33uF capacitor i have placed 0.1uF and instead of 500uF i have placed a 470uF cap (i only replaced them because that was available to me at the time).
So finally, whats the problem ?
When i powered the amp tubes light up and the status led was lit but after one second it went dead (did i mention this is my first tube amp build, and while soldering the board i have foolishly removed the resistor from the status indicator). Other than the status indicator not working the fuse did not blow and the tubes stay lit, and while there is some amount of hum coming from the speaker the sound from my guitar does not.
only when i max the preamp volume, master volume and treble some high frequencies bleed through to the speaker and fade away like tiny sounds. Sounds like there is a massive block somewhere in the circuit. There was no burning smell and no smoke when i powered the amp and as i can see the components on board look fine.
Sorry for the long writeup but as i checked everything and compared the layout of my build with the layout from this forum i really have no idea what might went wrong so any suggestion is more than welcome.
thanks in advance.