TrendsAudio PA-10 Tube Headphone/Pre Amplifier - Manual (Page 6)

Trends PA-10 User Guide
Section 9. Troubleshooting / Section 10. Accessories 11
10.2 DC Bias Voltage Tuning
Since each tube may derivate a bit in parameters, especially from different series, it
needs to re-tune the DC bias voltages to guarantee the machine is working in the best
point and performing the best sound quality.
There are two blue precise adjustable potentiometers (R3, R13) for tuning the DC bias
voltage of each channel. The DC bias has been tuned in factory. But after run-in for a
period or changed another tube, it would be deviated that the fine-tuning is needed.
Before you tune these, you need a screwdriver (take off the case), a small screwdriver
(turn the screw of the potentiometer) and a (digital) multi-meter to detect the DC bias
voltage.
1.
Use screwdriver to take out the two upper level screws in the front panel &
another two screws in the back panel. Then, open the upper case.
2. Power ON the machine with no audio signal input.
3. Wait at least 5 minutes for the machine to run in.
4. Use the multi-meter to detect the DC voltage between the test point A(L) [red] in
the PCB & the GND [black] (e.g. the ring of the power switch or the outer ring of
those RCA sockets) of the LEFT channel.
5. Turn the screw on the top of the R3 potentiometer by a small screwdriver
clockwise or anticlockwise until the voltage as close as to +16.5V.
6. Then, repeat step 4 and 5 for the RIGHT channel by changing the test point to
A(R) [red] and turning the screw on the top of the R13 potentiometer.
7. Power OFF the amplifier.
8. Cover back the upper case and tighten the screws.
Trends PA-10 User Guide
Section 11. Regulatory Compliance / Section 12. Contact Us 12
1 1 1 1 . . R R e e g g u u l l a a t t o o r r y y C C o o m m p p l l i i a a n n c c e e
This device complies with Part 15 of the FCC Rules. Operation is subject to the
following two conditions:
(1) this device may not cause harmful interference, and
(2) this device must accept any interference received, including interference that may
cause undesired operation.
Warning: Changes or modifications to this unit not expressly approved by the party
responsible for compliance could void the user's authority to operate the equipment.
NOTE: This equipment has been tested and found to comply with the limits for a Class B
digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide
reasonable protection against harmful interference in a residential installation. This
equipment generates, uses and can radiate radio frequency energy and, if not installed
and used in accordance with the instructions, may cause harmful interference to radio
communications.
However, there is no guarantee that interference will not occur in a particular installation.
If this equipment does cause harmful interference to radio or television reception, which
can be determined by turning the equipment off and on, the user is encouraged to try to
correct the interference by one or more of the following measures:
-
Reorient or relocate the receiving antenna.
- Increase the separation between the equipment and receiver.
- Connect the equipment into an outlet on a circuit different from that to which the
receiver is connected.
- Consult the dealer or an experienced radio/TV technician for help.
1 1 2 2 . . C C o o n n t t a a c c t t U U s s
ITOK Media Limited (Trends Audio)
Address:
Unit E, 13/F., World Tech Centre,
95 How Ming Street, Kwun Tong, Kowloon, Hong Kong
Phone: +852 2304 0730 (9am-6pm, HKG Time)
Fax: +852 2566-5740
Email: [email protected] (Sales)
[email protected] (Support)
Web: http://www.TrendsAudio.com