User Manual
TROUBLE-SHOOTING
NO POWER, NO INDICATORS, NADA - Probably something to do with AC power. Is it plugged in? Murphy's Law.
Check the fuse on the back panel. A blown fuse often looks blackened inside or the little wire inside looks broken. A very
blackened fuse is a big hint that a short occured. 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. Check the MAINS VOLTAGE SELECTOR if one is fitted. Some
of our models are able to have them and some don't. It should be set correctly for your mains voltage.
LIGHTS BUT NO SOUND - First try plugging the in and out cables into some other piece of gear to verify that your wires
are OK. Next check the front panel, try the PHASE (0-180) switch or PHANTOM. If you have sound now it might be a good
idea to turn up the levels to about 1 o'clock (rather than fully counterclockwise which is "minus infinity". The XLR inputs
and outputs are transformer balanced and floating. "Floating" refers to a very useful feature of transformers where they can
be used without a ground reference - this prevents ground loops before they happen rather than electronically cancel them.
Transformer "floating" inputs and outputs do not tie ground to the center tap. It allows the output to be equally happy driving
balanced or unbalanced inputs. This Preamp has both transformer floating outputs and transformerless unbalanced outputs
with +4 dBm nominal levels. The XLR outputs require that both PIN 2 and PIN 3 be connected (but not to each other). To
interface to unbalanced units you should connect PIN 3 to Ground or PIN 1. Brainless solution - use the 1/4" unbalanced inputs
and outputs to interface to unbalanced gear. Some low cost consoles use a stereo 1/4" jack for INSERTs. This has caused lots
of grief. These are unbalanced for both send and recieve. With transformer floating inputs and outputs PIN 3 must be grounded
(or connected to PIN 1) when used with unbalanced lines but not for balanced. No -10 dBv output is provided, but you can
turn down the input if you can live with 14 dB more hiss than should really be there
LEVELS SEEM TO BE WRONG, NO BOTTOM - Several possible scenarios - most likely a broken cable. 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 dBv = Zero VU. Generally RCA phono jacks are unbalanced -10dBv levels and most XLRs are balanced or pseudo-
balanced. This does not imply that all unbalanced lines are -10 or all XLRs are +4 or should be balanced. Manley provides
unbalanced +4 outputs on most of the pro gear. If one chooses to use this unbalanced output to drive a unit expecting -10 levels
(ADAT RCA jacks) expect plenty of level. 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. We do not provide that kind of switch because
of inevitable compromises in the signal path. 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
happening. 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 we are discussing the same levels, in most cases, you can use an unbalanced output
to drive a balanced input and a balanced output to drive an unbalanced input. Some pseudo-balanced op-amp circuits may
have problems driving an unbalanced input and also have problems driving transformers or 600 ohm inputs. The thing to really
consider is the levels appropriate for each input and output and not jump to conclusions because it says balanced or
unbalanced. Unbalanced simply means there is a signal and ground - balanced means 3 wires, 2 signals (opposite phase) and
ground.
ONE SIDE WORKS FINE BUT THE OTHER SIDE IS DEAD - Let's assume this is not wiring. We are pretty sure it is
the MIC PRE. If it were solid state you would generally send it back for repair. Being a tube unit, you can probably find the
problem and fix it in a few minutes. Not too many years ago, people could "fix" their own stuff by taking a bag of tubes down
to the corner and checking said tubes on a tube tester. These are practically extinct but no prob'. Most Manley gear is two
channel meaning you can swap tubes to determine the bad boy. Do two at a time just watching that they are the same number.
Be careful - there are some high voltages inside the chassis and tubes can get pretty warm but if you can replace a light bulb
you should be able to cruise through this. Just remember tubes use high voltages - Don't grab the circuit board! Before you
remove a tube, just take a look at them powered up. They should glow a bit and they should be warm. If one is not, you have
already found the problem. The tube's filament (heater) is burnt out or broken like a dead light bulb. The other big visual
symptom is a tube that has turned milky white - that indicates air has gotten into the tube or we joke "the vacuum leaked out".
Either way replace the tube. They are not hard to find - even Radio Shack carries a fair tube stock and Manley can ship you
a tested one. Back to swapping - before you pull a tube, pull the power out, let the unit sit and cool and discharge for a minute
or two, then swap, then power, then check. Gentle with those tubes, don't bend the pins by trying to insert them not quite right.
A little rocking of them as you pull them out or put them in helps. When the problem follows the tube you found the problem
- a bad tube. No soldering, no meters, one screwdriver - easy. 9 times out of 10 you can "fix" tube gear by replacing a tube
and you can verify that the tube is bad by swapping with the other channel.