18wattandlife wrote:
I recently purchased and built the MkII kit. Everything works pretty darn good except one small thing. Through an 8 ohm 4x12 cab it is perfect. When going through a 16 ohm 2x12 it squeals when the volume is about 8 on both channels. Sometimes fiddling with the EQ will tame it. But if I remember reading correctly if I switched the phase of the OT transformer inputs at the power tubes it should solve the issue. Is that correct? Because I can't find where I read that exactly.
You can try reversing the OT leads. Explanation from the manual Troubleshooting section "Squealing/Feedback", read that for more details.
"5. If all that doesn't work reverse the output transformer leads on pin 7 on V4, V5.
Explanation: One of the primary leads is in phase with one of the secondary taps. In a high gain amp, this phase relationship needs to be maintained." If that doesn't work, other steps may need to be taken. One thing to do it to move the wires around with a chopstick . Separate them well away from each other & shorten where possible.
18wattandlife wrote:
Also I was messing around with a 1p2t switch to toggle out the two 47k(or 470k I don't have the schematic in front of me) on V2 to add a little TMB extra gain. Would I still need the grid stop resistor on pin 3 of V2? I would obviously need a different switch to achieve that. Just curious.
The two 470K resistors form a voltage divider to effect changes to the gain. You can experiment with them if you like.
Next I add a cascade switch.[/quote]
You wont need to change the voltage divider above if you do that. Check unimind's post on his Mk. II mods. He built in a cascade switch.
Login
Register
FAQ
Search
