Schematic needed please for 70's Randall Alpha II RG150-2 with two 8419 tubes. Thank you.

[Helmholtz]

There must be a short in the winding somewhere in the 8 ohm tap..

If there was a short in the 8 Ohm winding, it would also make the 4 Ohm winding look shorted caused by transformer coupling. The 4 Ohm winding is typically part of the 8 Ohm winding anyway. I rather suspect an open connection/ bad contact.

[dmeek]

If you ever lift the board again, please post a photo of the foil side. I'm curious about the second trimpot. The schematic from the other site shows only the bias trimpot.

https://music-electronics-forum.com/...1&d=1587154023

[The Dude]

...... There must be a short in the winding somewhere in the 8 ohm tap..... I'm still investigating the jack. It is the 4 ohm jack that has the switch......

No. There is not a short in the winding. There is a short across the winding when the 4 ohm jack is not used. The 8 ohm tap also uses the 4 ohm winding. So, when you do not plug something into the 4 ohm jack first, the OT secondary is partially shorted loading the output via the switching jack. If you want to be able to use the 8 ohm output by itself with nothing in the 4 ohm jack, you'll need to remove the connection to the switching part of the 4 ohm jack so that it does not ground the transformer winding. I admit, it's either a poorly thought out design, or someone has modified the jack configuration. I won't even get into discussing using two output taps simultaneously. That's a whole other mess.