SDA

LA2A day

Author: matthew; Published: Nov 13, 2008; Category: Outboard Gear; Tags: , ; No Comments

Problem – Two of the Teletronix LA2As are behaving badly. One is noisy and one is not compressing appropriately.

Solution – Both compressors have noisy/scratchy gain pots, so I cleaned them with Deoxit. The box that isn’t compressing well gets a new T4-B and R25 because it’s handy, but nothing changes. I test the tubes on the non-compressor and find that both 12ax7s are pretty bad and the 6aq5 is really bad. I grab (and test) a good 6aq5, but we’re out of 12ax7s. I order some 12ax7s and a new FP-type filter cap from Antique Electronics. The now non-noisy LA2A is back in service with the non-compressing one standing by waiting for tubes and filter caps.

LA2A schematic

LA2A schematic

Thermionic Culture Vulture

Author: matthew; Published: Nov 8, 2008; Category: Outboard Gear; Tags: , , ; No Comments

Problem – The Thermionic Culture Vulture isn’t passing signal on the right side.

Solution – This thing eats an EF86 tube about every seven months. I replaced the one on the right with a known good one and the piece soldiers on. I tried the bad tube on the left and it made the left bad. Troubleshooting! The tube is operating within spec and there aren’t any physical problems I can see that would cause it to fail.