Sphere MP-1 Mk.3.3, Руководство пользователя

Страница: 8 / 10

TROUBLESHOOTING TIPS
Front panel LEDs on the power supply don't light up: Check the rear panel fuse
and verify that the power cord is plugged in.
Buzz, hum: Make sure that the power cord is plugged into a properly grounded
outlet. The MP-1 supports the AES file 48 (balanced line standard) however a
lot of other high end audio products do not. This can result in ground loops.
If you are trying to operate the output of the preamp with single-ended
equipment, buzz may occur if the conversion from balanced to single-ended is
not handled properly. Contact Atma-Sphere for assistance. In some situations
an isolation transformer can be helpful.
Distortion: Check the output tubes (6SN7, upper right in diagram) and the
associated 6SN7 in front for defects. If any of the output pins of the main
output XLR connectors other than pin one is at ground potential, distortion
may result. Also check the circuit board fuses in the power supply:
One or both channels out: Check all tubes. If OK, there are two fuses located
on the right side of the power supply circuit board (as you face the front of
the unit), one for each channel. Replace with the same type slow blow fuse (1
Amp for 117 Volt units, 0.5 Amp for 230 Volt units). If you are not qualified,
do not remove the cover. Hazardous or lethal voltages are present with the
cover removed. Refer service to qualified service personnel.
Noisy phono section: Replace the 12AT7s in the phono section. AVOID 'NOS' (New
Old Stock) TYPES AT ALL COST! Despite claims to the contrary by NOS tube
suppliers, all NOS 12AT7s are just too noisy if you intend to use low output
moving coil cartridges. Mullard- Telefunken- don't care. They are too noisy.
The quiet ones were purchased decades ago.
Low output from one channel: Check tubes.
DC Offset LED lit up continuously: Check the 6SN7s (rear right two on circuit
board) in the channel associated with the LED.
NEVER, EVER, USE TWEEK OR ANY CONTACT ENHANCER ON TUBE SOCKETS! Tweek is
resistive at vacuum-tube voltages. This will destroy the tube sockets and
possibly the circuit boards!
If none of these suggestions help, contact your dealer or ATMA-SPHERE MUSIC
SYSTEMS.
MORE TIPS AND TWEAKS
For use with subwoofer and other bi-amplified systems: Have your crossover
updated with correctly balanced inputs. If this is not possible, a specialized
balanced-to-unbalanced subwoofer-optimized line transformer is available from
Atma-Sphere and works quite well. If you do not use one of these techniques,
it is likely that you will encounter a buzz.
When ordering from any source, specify tubes for a differential circuit
(matched tube sections). The 12AT7s at the input of the phonograph section and
the 6SN7 at the input of the high level section (right front on circuit board)