Manley ENHANCED PULTEC EQP1-A EQUALIZER - Manual (Page 9)

There are a number of possible symptoms of something not quite right, some may be interfacing, others we will touch
on as well. On the back panel are balanced and unbalanced inputs and outputs. Usually we connect balanced outputs to
balanced inputs (same with unbalanced) but usually we can also patch an unbalanced to balanced or balanced to unbalanced
with no problem (especially true with transformers) but some gear you can't. Check the manuals if you find a problem.
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. 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. Assuming that it was OK into the other unit it probably is still a wiring thing. The XLRs are transformer balanced
(isolated / floating) that require the LOW or negative part of the signal on PIN 3 to be connected to something, even when
driving unbalanced inputs. With unbalanced sends or returns are used with the EQ balanced inputs/outputs then PIN 3 and
GROUND should be connected together. The EQ's unbalanced outputs kill the balanced XLR signals to provide a
transformerless audio path. Once again, when using a balanced to unbalanced (or vice versa) don't forget to have PIN 3
connected to the SLEEVE of the 1/4" plug.
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. 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 you
have two and only one EQ exhibits this problem, it may be a problem in that unit. See the next item.
SIGNAL GONE EVEN IN BYPASS - The signal goes through the tube stage in "Bypass". Let's assume wiring has been
eliminated as suspect. There is about a 98% chance it is a tube. 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 (your parents)
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'. 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. 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. You can even pull a
tube or two from a guitar amp to verify "it was that one not glowing" but then get an exact replacement (substitution list on
previous page). Before you pull a tube, pull the power out, let the unit sit and cool and discharge for 10 minutes, 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. The good news is "easy" the bad news is, tube life is not very predictable.
HUM - Once again - several possibilities - several cures. Most likely it is a ground loop. If you are using the 1/4" unbalanced
inputs, try the transformer XLRs. Balanced inputs can reject hum from ground loops, but it would be good to break the loop.
The two most common procedures are: try a 3 pin to 2 pin AC adapter (about a dollar at the hardware store) which is better
than messing up the power cable by bending the ground pin until it breaks off. Method two - cutting the shield on one side
of the cable. This is usually done at every female XLR to "break" all loops. You may get a loop simply from the rack. All
the other gear in the rack is "dumping" ground noise onto the rack rails. Try removing the EQ from the rack so that it is not
touching any metal. You may have cured a non-loop hum. Some gear radiates a magnetic field and some gear (especially if
it has transformers) might receive that hum. A little distance was all it took. A cool method of reducing all sorts of hum and
noise is to use the new 60-0-60 balanced AC power transformers available from Equi=Tech and Furman. It costs more but
works best. Hum might be because of the unbalanced input but this hints at ground loops and questionable wiring.
TROUBLE-SHOOTING
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