Recently my longtime trusted Eico 1030 regulated high voltage DC power supply succumbed to a catastrophic failure — a shorted transformer winding. The power transformer has a separate winding that supplies screen voltage to the 6L6 pass tubes. This is a half-wave circuit that was rectified by one original 1N4006 silicon diode. Unfortunately, this old […]
Transformers can blow in the blink of an eye Read More »
I wanted to write about a unique problem in a Rockola model “O” jukebox amplifier (from a Rockola 1426 jukebox, vintage 1946). The amp is a very primitive design: class A, 4 tube operation consisting of 5U4 rectifier, push-pull 6L6’s, and 6J5 preamp tube. An interstage transformer drives the P-P 6L6’s instead of a more
rare Rockola jukebox amp hum problem Read More »
For tube fans, today’s Pluggers comic strip conjures memories of the NATIONAL RADIO NEWS magazine cover, Aug-Sept 1945 issue. The Pluggers comic is in today’s newspaper July 23, 2011, or you can enjoy the comic online at Comic Strip Nation, comic link is HERE. I mention this comic because many fans of old tube gear
Pluggers comic conjures ‘National Radio News’ Read More »
©2011, Bob Putnak. This post examines the performance (directly related to the input impedance) of low-cost meters; specifically, I explore a common multipurpose Colluck PM-128E DPM (digital panel meter) and a bargain-priced Cen-Tech #98025 multimeter. Limitations in the design of these low-cost meters can severely affect measurement accuracy. First of all, I prove that the
Limitations of cheap DPM’s and DMM’s Read More »
Meet the TubeSound TTM-1: Testing of almost all amplifying tubes (triode, tetrode, pentode, beam power) from antique 4-pin (such as a #10, #45, or #50) through 9-pin novar (such as a 7868). Socket configuration — 4-pin, 5-pin, 6-pin, 7-pin medium (aka 1625), 7-pin miniature, octal, loctal, 9-pin-miniature, and 9-pin novar. All tests use exact tube
TubeSound TTM-1 Tube Tester & Matcher Read More »
