Manley SNAPPER - Manual (Page 7)

More Tube Tawk (while we’re at it)...
How can I tell when I need to replace them? Most problems
relating to the output tubes will show up while performing the
bias procedure (on the next page). Tubes that cannot be
adjusted within the specified range or have a very unstable
reading are should be replaced. If the tube s plate (the grey
metal rectangular box-like part most visible from the outside)
is glowing cherry red or orange, then the tube is severely
overheated. Check its bias immediately; if unable to adjust,
then turn off the amplifier right away and replace the tube.
The input and driver tubes can become noisy (hiss) or the
amplifier may exhibit audible distortion; substituting known
good tubes is the best way find the bad one. You got 2
channels to play with! They all can’t be bad at once.
All tubes are microphonic to some extent; that is, they will
make ringing noises through the speakers when tapped or
vibrated. Here again, substitution will determine which one is
overly sensitive to mechanical vibration. Obviously, any tube
that is totally dark inside while powered up or is cold to the
touch (careful!) is defective, or not making good contact with
the heater contacts in the tube socket.
Most tubes have a silvery coating deposited on some area
inside the glass bottle. This coating is put there by the getter ,
and its job is to soak up or get contaminants, such as air
molecules left over inside the glass envelope during the tube s
manufacture, and help keep the vacuum hard. If the getter
material has turned white (compare to another tube), then the
tube has lost vacuum (or gained air!) and is definitely bad.
Replace at once. Don t turn the amp on. Throw the tube out.
Do I need to replace them all at once?
No, at least not with these amps, or unless all the tubes have
clocked some thousands of hours of use. Some tube amps do
require that if one tube has to be replaced that a complete
matched set put in. All Manley amps use individual bias trims
for each output tube which allows a single tube to be replaced.
Absolute best performance is achieved when the tubes are
most similar, both in bias requirements and transconductance
characteristics. We batch them and label each tube so that in
the event of a replacement you can get one from Manley of
similar characteristics as the others in your amp. We need that
hand written number on the top of the tube (Output tubes only.
We know what we need to give ya for input or driver tubes).
Does the sound of the amp change as the tube ages?
Yes, but not too much, and even then, given good tubes, it is
fairly strongly related to the amp design. The tubes can be
allowed to reach their technical life limit, or they may be
replaced more frequently depending on the listener s taste
and accompanying equipment. In general, the band edges will
suffer first, with very gradual loss of the deepest bass and
ultrasonic treble. The SNAPPER is designed to meet stated
power bandwidth specifications at 80% of rated output power
at the end of useful tube service life.
By way of contrary tube application contrasts, it is not like
big guitar amps where tubes are replaced every 6 months for
reasons of tone . The SNAPPER s tubes are arranged to
operate in a quite conservative operating regime, allowing a
very long life and less change between old and new tubes.
This is where that figure of 2000 hours, or 4 to 5 years of use
comes from. You may notice an improvement between tubes
this old and new tubes depending on how critical you are.
Keep in mind the sound of new tubes changes most in the first
weeks of use before they can be considered broken in . At
first they may sound a little tight and direct
(like some
people we know).
Is it difficult to replace a tube? Yes, but only if you have
trouble replacing light bulbs. It is super easy. Turn off the
power. Just let the amp cool a few minutes so that you don t
burn your pinkies. It helps to wiggle the tube gently rather
than pulling it out straight. Use some terry cloth material or
an oven mitt if time is pressing.
Even if you don t consider yourself technical you probably
have more technical ability than your parents and they used
to fix the family TV set by taking out the tubes and putting
them through the tube tester at the local pharmacy. It is
almost as easy to re-insert a tube. Just make sure it is correctly
lined up with the socket and you don t bend a pin. Notice that
the 9-pin miniature tubes have a gapped set of pins, making
a rotational installment error nearly impossible. The larger
8-pin or octal-based tubes have no gap in their pin sets, but
instead have a larger keyed center pin formed from the inert
plastic plug material. The key makes insertion of the tube into
the socket nearly impossible unless the key lines up with the
matching hole in the amp s octal socket. Notice that octal
tubes which have damaged or missing keyed center pins
should NOT be used, since some output tubes internal wiring
can cause dramatic equipment failure by short-circuit if
incorrectly fitted to the amp s sockets.
You can wiggle the tube when reinserting too. If you had a
solid state amp (heaven forbid!), transistor replacement
would merely be chapter 1 in the saga. You would have to
open it up, diagnose the bad transistors and burnt resistors,
de-solder ’em, find replacements (good luck on locating
those germanium beasties) re-solder ’em, and hold your
breath as you turn it on. Best have your Platinum credit card
handy for ordering more. Or you could send it back, be
without music for a few weeks, pay for service by the hour
and be ready to administer nitroglycerine tablets under the
tongue when it fries again.
That’s why TUBES RULE: If you need a tube, or set of
tubes, Manley Labs will be happy to sell you matched sets at
a good price. And if you prefer to send the unit back for repair
or adjustment, our warranty covers most everything except
tubes (6 months only please) and abuse (7 months only-- just
kidding). Plus we handle ground shipping back to you
(unless you live overseas, cuz there’s no ground service!)
Repairs usually take less than a week. Could we do more?
(That’s a rhetorical question. It’s late. Just keep reading...)
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