RichardH
Bodging pleb
Around 1986 Linn started putting this zener/resistor/zener circuit as stock on the Valhalla. It is very easy to install and is the second most cost-effective upgrade you can make to an LP-12 (after the "bolt" mod).
It doesn't turn your Valhalla into an Armageddon but is well worth the cost and effort. When reselling or buying a used Valhalla, it's also an indicator to its age.
The Zener Diode Mod is quite simple to do. Only three parts are required; one 12k resistor (1/4 watt is OK) and two zener diodes. These parts are very common and available everywhere. The only tricky part is ensuring the dark band marker end of the zeners are soldered to the resistor. Trim the excess leads. Then just loosen the blue and grey motor screws and install. Tug gently on the motor wires and zeners to be sure everythings secure and that's it. On later stock Valhallas, this mod is actually part of the circuit board soldered right next to the motor lead screws.
For a diagram of the mod, visit the Analogue Addicts LP12 FAQ and search for "zener" on the page. They recommend zener diode 1N5266B.
Source: Ron the Mon
It doesn't turn your Valhalla into an Armageddon but is well worth the cost and effort. When reselling or buying a used Valhalla, it's also an indicator to its age.
The Zener Diode Mod is quite simple to do. Only three parts are required; one 12k resistor (1/4 watt is OK) and two zener diodes. These parts are very common and available everywhere. The only tricky part is ensuring the dark band marker end of the zeners are soldered to the resistor. Trim the excess leads. Then just loosen the blue and grey motor screws and install. Tug gently on the motor wires and zeners to be sure everythings secure and that's it. On later stock Valhallas, this mod is actually part of the circuit board soldered right next to the motor lead screws.
For a diagram of the mod, visit the Analogue Addicts LP12 FAQ and search for "zener" on the page. They recommend zener diode 1N5266B.
Source: Ron the Mon