Manley TNT MICROPHONE PREAMPLIFIER - Manual (Page 19)

TROUBLESHOOTING
There are a number of possible symptoms of something not quite right; some may be interfacing, others we will touch on
as well. If you suspect a problem, the following paragraphs should help.
NO POWER, NO INDICATORS, NADA - Probably something to do with AC power. Is it plugged in? Check the fuse
on the back panel. A blown fuse often looks blackened inside or the little wire inside looks broken or it’s resistance meas-
ures higher than 2 ohms. A very blackened fuse is a big hint that a short occurred. Try replacing the fuse with a good one
of the same value and size. If it blows too, then prepare to send the unit back to the dealer or factory for repair. The fuse
is a protection device and it should blow if there is a problem. If the unit works with a new fuse, fine, it works. Some-
times fuses just blow for unknown reasons.
LIGHTS BUT NO SOUND - First try plugging the in and out cables into each other or some other piece of gear to
verify that your wires are OK. If not fix them or replace them. Assuming that cables passed sound - it probably is still
a wiring thing. The output XLRs are transformer balanced which require both PIN 2 and PIN 3 to be connected some-
where. When driving an unbalanced input (inserts on some consoles) PIN 3 needs to be grounded or connected to PIN
1. Same with the unbalanced 1/4 inch jacks - if driving a balanced input you can’t ignore the negative side. It needs to
be connected to the sleeve of the phone plug. Another way to do basically the same thing is join PIN 1 and PIN 3 on the
XLR male at the destination. Easiest way - Use the balanced with balanced, unbalanced with unbalanced. That is why the
options are there.
LEVELS SEEM TO BE WRONG, NO BOTTOM - Several possible scenarios. Manley uses the professional standard
of +4 dBm = Zero VU = 1.23 volts AC RMS. A lot of semi-pro gear uses the hi-fi reference of -10 dBm = Zero VU. This
is a 14 dB difference that will certainly look goofy and may tend to distort. Often there are switches on the semi-pro gear
to choose the pro reference level. If the loss looks close to 6 dB and it sounds thin then one half of the signal is lost. The
cause is probably wiring again. One of the two signal carrying wires (the third is ground / shield on pin 1) is not happen-
ing. Check the cables carefully because occasionally a cable gets modified to work with a certain unit and it seems to
work but its wrong in other situations. If only one side of the TNT exhibits this problem, it may be a problem in the TNT.
HUM - Once again - several possibilities - several cures. Most likely it is a ground loop. Ideally each piece of gear
should have one ground connection and only one. However, the short list of grounds include the AC mains plug, the
chassis bolted to a rack with other gear, each input and each output. The two most common procedures are: try a 3 pin to
2 pin AC adapter (about a dollar at the hardware store).This while legal in many countries can be dangerous. Method two
- cutting the shield on one end of each cable. This is done by some studios at every female XLR to “break” all ground
loops. All the other gear in the rack is “dumping” ground noise onto the ground. Try removing the EQ from the rack so
that it is not touching any metal. You just may have cured a non-loop hum. Some gear radiates a magnetic field and some
gear (especially if it has audio transformers or inductors) might receive that hum. A little distance was all it took. It is
worth a few placement experiments if you notice hum.
IT MAKES NOISES WHEN THE FRONT PANEL IS TAPPED - An easy one. Some tubes become microphonic
over time. That means they start acting like a bad microphone. Vibration has caused the supports for the little parts in the
tube to loosen and now the tube is sensitive to vibration. Easy - Replace the tube. Which one? The one that makes the
most noise when you tap it. Usually this will be the smaller tube closest to the front. The TNT will have to be on, con-
nected and speakers up but not too loud for the sake of your speakers.
Further Questions? Please contact our Service Department:
+1 (909) 627-4256 x325
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