Dead Amp Checkout

Fender

In <19980204075001.CAA1838--(at)--adder03.news.aol.com> myoshi--(at)--ol.com
(Myoshi3) writes:
>
>OK, I know someone can help me out here! My SF DR (late model with
the
>push-pull volume boost standard) has just died on me. There is no
output at
>all. The tubes still light (nice healthy red glow with a bit of blue
on the
>center beam), the pilot light still lights, but nothing comes out...
Not even
>the usual 60hz hum that I've grown to love. Anyone know what this
might be?
>
>Thanks in advance,
>Mike

Lord Valve Speaketh:
Well, if you have blue in the power tubes, you have B+. Orange means
you have filament voltage, also confirmed by the fact that the pilot
lamp is lit. I'm assuming you've tried to play through both channels,
and that neither worked. So...possible problems, in order of
likelihood:
1) Open speaker wire. (Broken, or disconnected from terminal.) If you
find that this is the problem, check the power tube sockets for arc
tracks between pins two and three. If you see any, you MUST
replace the socket, AND THE TUBE THAT'S IN IT. This may show up
on either side of the socket, so you'll have to take a peek inside
the amp to be sure.
2) Open voice-coil. (Also check the sockets as above.)
3) Shorted speaker wire. (This will knock all the hum off the output,
but if you play with the amp turned way up, you'll still be able to
hear a little bit of very fuzzy-sounding output from the speaker.)
4) Bad phase-inverter tube. This is the 12AT7 right next to the power
tubes.
5) Shorted output transformer secondary. It'll give the same symptoms
as #3.
6) Open output transformer secondary. Again, check the sockets for
arcing.
7) This might sound stupid, but I've seen it many times. Check to see
if the speaker wire is plugged into the "SPEAKER" jack, and NOT the
extension speaker jack. If that is the case, it'll give the same
results as #3.

Lord Valve
Website at: http://www.freeyellow.com/members2/lord-valve/
"I got the chop...I'll never get popped." - Tower of Power

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