Voyager volume envelope fault. No right output

The Moog Forum Minimoog Forum
1

Hello

My voyager has developed a fault, can anyone help me track down the cause?

a few weeks ago, the right channel output stopped working, at the same time the dials for the volume envelope stopped working. It now operates as if there is no attack, and full decay at all times.

When the fault occured, I had the headphone output connected to the pan CV input.

I am pretty handy with a soldering iron, and would be comfortable effecting my own repair, however I am totally unfamiliar with the internal circuits, and help would be greatfully recieved.

Many Thanks
Dan

2

You killed U49 (LM837) on the analog board. It’s not a good idea to use a mono plug into the headphone jack cause the right channel is shorted.

Rudi

3

Rudi, I love you! thanks

Is it possible that anything else further along the line has suffered damage?

I have also used the headphone O/P to drive filter, and Vol CV’s. Do I risk similar damage, or is this limited to just the pan input?

Thanks again.

4

The headphone output is low impedance to drive 32-600 Ohm headphones. When you make a short with a mono plug the opamp of the right output gets hot and this opamp is only one of a quad opamp. The other opamps controls for example the envelope for the master output. When all four opamps are dead you will get the faults as they are now on your Voyager. It’s really better when you are using the headphone outputs only for headphones.
Please cut all pins of the chip and desolder each pin carefully. I’m using an AMP socket for the new chip.
Have fun,
Rudi

5

Hi,

The repair is complete, and my voyager is back to full strength.

Many thanks for the help, I’d have been lost without it.

Dan
:smiley: :smiley: