Twin Build Questions

[benoit]

1. On the Fender AB763 Schem from the TAB, the schem says all resistors 1/2 watt unless other wise marked. Does this apply to pots?

2. What does RA mean on a pot? A is audio and L is linear, correct?

3. Some pots have more values than just type and resistance, like 50k - RA - 2 - 35 for the intensity pot. What do the 2 and 35 represent? I'm guessing watts and something else?

4. Any recommendations for the recto diodes? I don't even know where to begin there in terms of necessary voltage/current rating. Obviously I need diodes that can take at least 340v (PT secondary voltage) but how much margin do I need, and are there current or power ratings involved?

[Beerman]

Check the Schem and Layout for Weber's 6A20..... might have more information.

[Darkbluemurder]

1. On the Fender AB763 Schem from the TAB, the schem says all resistors 1/2 watt unless other wise marked. Does this apply to pots?

2. What does RA mean on a pot? A is audio and L is linear, correct?

3. Some pots have more values than just type and resistance, like 50k - RA - 2 - 35 for the intensity pot. What do the 2 and 35 represent? I'm guessing watts and something else?

4. Any recommendations for the recto diodes? I don't even know where to begin there in terms of necessary voltage/current rating. Obviously I need diodes that can take at least 340v (PT secondary voltage) but how much margin do I need, and are there current or power ratings involved?

1. Not sure but in good designs (such as the Twin Reverb) there is no significant DC going through the pots.

2. RA = Reverse audio

3. no idea

4. A typical arrangement would be 3 IN4007 diodes in a row. Wiring diodes in series increases the PIV (peak inverse voltage). There are diodes with higher PIV rating than IN4007. 1kV should be good.
BTW I always wondered why tube rectifiers should be more prone to failure than solid state rectifiers. Since I started working on amps (only since December 2001) I have blown 2 solid state rectifiers but never a tube rectifier.