Roland Super Cube 100 LED

[bobloblaws]

In any event I went ahead and tapped off the secondary AC and used the existing components to implement the suggested fix. Working as advertised. Thanks for your help and patience guys!

[vintagekiki]

Draw how connected LED so we can learn something new too.

[bobloblaws]

OK, I just discovered something that should shed some light on this snafu. In my diagram I drew the one end of the 3.9K resistor as grounded based on a continuity check with the DMM. I'm not sure where the ground connection is but it turns out that end of the resistor is in fact already connected to the same leg of the bridge rectifier that I tapped for my AC voltage. So I've put both ends of the resistor back to their original places and left my jumper to ground connected to the cathode of the LED and everything is peachy keen. Why the cathode was connected to the 1nF cap on the circuit board instead of ground as in the other instances I've seen remains a mystery to me.

Thanks again for all your help with this.

[vintagekiki]

Why the cathode was connected to the 1nF cap on the circuit board instead of ground as in the other instances I've seen remains a mystery to me.

There is no 1nF capacitor in the schematic for the LED indicator (see attachments), only R47, D8 and D9 are connected in half seconds PT.
I have to ask. Are you sure understand schematic?
R47, D8 and D9 must not come with primary AC voltage of 117 VAC

[bobloblaws]

There is no 1nF capacitor in the schematic for the LED indicator (see attachments), only R47, D8 and D9 are connected in half seconds PT.
I have to ask. Are you sure understand schematic?
R47, D8 and D9 must not come with primary AC voltage of 117 VAC

I have to ask, have you been paying attention? Did you look at the diagram I made of the Super Cube 100?

[vintagekiki]

I have to ask, have you been paying attention? Did you look at the diagram I made of the Super Cube 100?

Yes I have paying attention and your diagram in post # 1 LED_circuit.jpg is incorrect.
Which is incorrect writes in post #4 and post #7.

People say who knows understands, who doesn't know he doesn't know.

[bobloblaws]

Yes I have paying attention and your diagram in post # 1 LED_circuit.jpg is incorrect.
Which is incorrect writes in post #4 and post #7.

People say who knows understands, who doesn't know he doesn't know.

I appreciate your willingness to help, VK.

[vintagekiki]

Thank you!

[g1]

it turns out that end of the resistor is in fact already connected to the same leg of the bridge rectifier that I tapped for my AC voltage. So I've put both ends of the resistor back to their original places and left my jumper to ground connected to the cathode of the LED and everything is peachy keen.

So it turned out the resistor was getting it's AC source from the PT secondary like in this schematic?
And you were missing the ground between the LED cathode and the 1nF ?
I'm going to guess someone installed 3rd prong ground, clipped the ground side of C31 ("death cap"), so you no longer had the ground for the power light circuit.
No part of the circuit should have ever connected to the primary, but someone clipped the wrong end of C31 and did not restore the ground to D9.

[Enzo]

So none of the parts were ever bad?

[vintagekiki]

Road to hell always has been paved with good intention.