Manley SHRIMP - Manual (Page 9)

It is rare that any of these problems occur but if they do here are some things to try.
HUM - Try a mains ground adapter if they are legal in your country. They are also called 3
pin to 2 pin adapters or "cheaters" and are available in hardware stores. There should be
one ground in your system and only one. If two or more pieces of gear have 3 pin AC
cables a ground loop can occur which will usually cause hum. The Shrimp is probably the
best single piece to ground as it is the center of your system. But you never know...
HISS - Usually one of the sources. This source may have a volume control that is turned
down and forcing you to turn up the volume of the Shrimp. Adjust the source so that it is
a similar volume as your other sources. If it seems to be the one channel of the Shrimp,
then it is probably an input tube (12AT7WA). Most tubes should last many years but
sometimes they get noisy prematurely for no good reason. To verify, you can swap the
two 12AT7s (with the power off) then test again. Be careful - tubes can be hot, don't bend
any pins and gently wiggle the tube to remove it or insert it. Force should not be needed.
BALANCE - The two speakers sound different - Assure that the BALANCE control is
centered. It may be the CD or source and the way it was recorded. First try a different
source. Next try swapping the inputs. Power down and swap left and right inputs. If it is
the source, then the problem will "follow" the swap. Return them to normal (L=L). Power
down again and next try swapping the Shrimp's outputs. If now the problem follows the
swap, then the Shrimp may have a problem and the tubes inside the Shrimp should be
swapped between left and right channels one at a time to see if a rogue tube is causing
this headache. If the Shrimp appears not to be the problem, then try swapping the speaker
connections by putting the left speaker wire in the right terminals and right wires into the
left terminals of your power amplifiers. If the problem switched sides then the power
amplifier on that side has a problem and you will need to contact the amplifier's
manufacturer. If the problem is still on the same side after all this swapping all the way
from source to speaker, then it is probably a damaged or fatigued speaker.
ONE CHANNEL DEAD - Usually just a bad connection or an interconnect is plugged in
wrong. Check your wiring. You can try any of the other 4 inputs and verify that both
channels work on other inputs or not. The Balance Control is centered? Do all those
swapping tests as outlined above in the "balance" section of this page to see who is dead.
If you determine the Shrimp has one channel dead, most likely problems is a bad tube
(12AT7 or 7044). Wait at least 15 minutes after turning off the preamp and unplugging
the power. There are plenty of high voltages running around inside the Shrimp when
power is on and it takes a while before the power supply capacitors discharge so there
could still be volts there even when unplugged - so be patient and let the power supply
discharge before taking off the top cover and poking around. There is a SHOCK
HAZARD unless you follow these directions. The current is low and it is DC which
means we are not talking "lethal" but it can hurt, arc and burn, not to mention make one
jump and yell nasty four letter words. Also, use one hand - not two. Wearing a cotton
glove insures that there won't be any surprises.
9
TROUBLESHOOTING