Re: Roadking series 1 bias issues

[i_want_the_chair]

Okay, so I tried unsuccessfully to do a bias mod to my RK ser 1.... now I have returned all back to it's original specs BUT... I am having massive issues with a 'floating' bias voltage. I am getting readings of up to 300mV (before I quickly turn it off) across all 6 power tubes (only reading 1 tube at a time though). The only way I can get it to stabilise around the 50mV range is to remove the 4 6L6's, so only the 2 EL34's are in the sockets and flick the amp to diode tracking. I have passive tested all the components on the power stage and none are showing any fault...... Any idea's?

 

[domct203]

Okay, so I tried unsuccessfully to do a bias mod to my RK ser 1.... now I have returned all back to it's original specs BUT... I am having massive issues with a 'floating' bias voltage. I am getting readings of up to 300mV (before I quickly turn it off) across all 6 power tubes (only reading 1 tube at a time though). The only way I can get it to stabilise around the 50mV range is to remove the 4 6L6's, so only the 2 EL34's are in the sockets and flick the amp to diode tracking. I have passive tested all the components on the power stage and none are showing any fault...... Any idea's?

What was un-successful about your original bias mod?

Are you 100% certain you did not damage the PCB? You may have destroyed a trace on the underside of the board, especially if you were repeatedly re-heating a joint to Mod/un-mod, or perhaps you have poor/cold solder joints.

How did you "passively" test the components, and why are you messing around in the power stage of the amp? If you were attempting to mod for adjustable bias you should only be working in the bias supply circuit.

Is there a schematic you were trying to follow?

Dom

 

[i_want_the_chair]

unsuccessful meaning it didn't work at all... I will check the solders again but I think they are all ok, passive test meaning without power on, so I wasn't testing voltage over a resistor, just checking that it was the value it is meant to be.

 

[domct203]

Maybe if you share exactly what you did we can help. The RK is a little different in the bias supply because of the Progressive Linkage. Where were you modding?

Dom