Manley JUMBO SHRIMP - Manual (Page 9)

TROUBLESHOOTING
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 “bal-
ance” 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, 5670, 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