Owner`s manual
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. Or try one anyway unless you
fear the Electricty Police. A mains ground adapter is also called a "3 pin to 2 pin adapter" or a
"cheater" and is available in hardware stores. There should be one ground to the wall 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 Stingray is probably the best grounded single piece as it is the
center of your system.
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 Stingray. Adjust the source so that it is a similar volume
as your other sources. If it seems to be the one channel of the Stingray, then it is probably an
input tube (12AT7WA). Most tubes should last many years but sometimes they get noisy
prematurely. 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 - 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 speaker connections by putting the
left speaker wire in the right terminals and right wires into the left terminals. If the problem
switched sides then the Stingray is suspect, if the problem stayed on the same side 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? You might try swapping the speaker
interconnects at the Stingray end. If the problem swaps sides then it may be the Stingray. The two
most likely problems is a bad tube (12AT7 or 6414) or a blown 250 mA (MDL 1/4) B+ fuse
located in the Stingray. If you get NO BIAS READING on all 4 tubes on a channel, then you
have blown that channel's internal B+ fuse located on the PCB inside the amp. Wait at least 20
minutes after turning off the amp and unplugging the power. There are about 400 volts DC on
these fuses 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 bottom 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 you 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.
TUBE GLOWS CHERRY RED. This is where you can see the plate area of the tube glowing red hot
(they are normally gray or black and are the most visible part inside the tube).This indicates a bias
problem or a bad tube; immediately attempt to re-bias the tube in question (see page 15). If the
bias cannot be adjusted on that tube, immediatley turn off the power; the tube will have to be
replaced. It is normal to see a slight blue glow that seems to coat the inside of the glass. It is also
normal if a tube "flashes" bright white on turnon. Do not worry about this.
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