Monday, December 3, 2012

New project: Heathkit W-2 tube amplifier rebuild

Things are never quiet here at the 6th Street Bridge.  Having just finished up the 1625 amplifier, I decided yet another project was worth pursuing.  This time it's yet another rebuild of a vintage piece of gear - the Heathkit W-2.  This was a fairly popular "20W" mono amplifier made in the early to mid-1950s.  It uses the classic Williamson circuit with 6SN7 driver tubes, 5881 output tubes, and Peerless output iron - running in Ultralinear.  Another special thing to note is the separate chassis for power supply and the signal which is a great way to reduce hum.

The W-2  I received was in pretty good condition.  Popping the hood and the resistors and capacitors look to be in mint condition.  But sadly, the amplifier didn't work.  Not a single hum, burp, or anything out of the test speaker.  A quick diagnoses with the multimeter and it appears that the original builder had neglected to ground the two chassis together via the umbilical cord!  A short length of wire, two solder joints, and music was coming out the speakers.  It makes me wonder if I was the first to ever hear this particular amplifier.  Very weird to say the least.

Anyway, the sound - with almost 60 year old passive parts - was rather lifeless: undynamic with some treble roll-off..  Here's hoping that some coupling and power supply capacitor upgrades will bring this old amp up a couple of notches.  Of course I also need to score another unit so I can listen to stereo.