Powering up old amps

From Dr.Distortio–(at)–bs.mhv.net Wed Jun 7 13:15:08 CDT 1995
From: Dr.Distortio–(at)–bs.mhv.net (Dr Distortion)
Newsgroups: rec.audio.tech,rec.audio.misc
Subject: Re: Powering up old equipment
Date: 7 Jun 1995 17:42:11 GMT
Xref: geraldo.cc.utexas.edu rec.audio.tech:16167 rec.audio.misc:9610

mark vanroojen (ms–(at)–nlinfo.unl.edu) wrote:
: Oh yeah, If the unit in question has a tube rectifier, the filter
: caps will not see much in the way of voltage until that rectifier
: starts to conduct. And it probably won’t conduct until after the
: voltage gets up to 50 volts or so. (Since the filament needs to heat
: up before it will conduct.) With a solid state rectifier, it
: will conduct right away.

I have a standard procedure I use when a piece of old gear that’s been
idle for years comes into my shop. First, I remove all the tubes, plug in
a solid-state rectifier in place of the tube rectifier (if applicable),
and bring up the line voltage gradually over the course of an hour or so,
monitoring voltages throughout the amp and keeping an eye on the filter caps.
While the caps are forming, I test all the tubes I’ve pulled out of the
amp for the usual parameters, using my trusty TV-7. Then I power off the
amp, re-install the tubes, hit the “on” switch and pray 🙂 It’s worked
well for me so far. While I have the amp open, I also clean out what
filth I can get at easily with a clean rag, a small vacuum and a can of
compressed air. I also dab any rusty transformer laminations with a soft
brush dipped in black Rust-Oleum.


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