Version 1.32
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down (anti-clockwise) so that the voltages are not affected by the output signal. The
voltages can be measured with the amplifier stood up on one end. Be careful here as
standing on its end is very unstable and catching an amp that is falling when switched
on could present a shock hazard. Prop the amp up and make sure that it is secure
before switching on.
WARNING: CARE MUST BE TAKEN WHEN CARRYING OUT THIS PART OF
THE PROCEDURE AS THERE ARE DANGEROUS VOLTAGES INSIDE THE
AMPLIFIER. IF UNSURE, PLEASE SEEK ASSISTANCE FROM A QUALIFIED
ENGINEER.
Please note that these voltages may vary slightly due to variations in the mains
supply, and valve and component tolerances. Note: a variation of approximately 10%
is acceptable without any detrimental problems.
1.
On the power supply PCB measure the voltage between X17 (ground), and
X18. For PSE mode this should be approximately 460V- 490V DC. For Push
Pull this should be approximately 460V DC. Depending on mains voltage.
2.
The Cathode bias voltage (pin 8) for each EL34 should be approximately 35V
DC. This is measured across the 470R 7W resistors, and is relatively important
to prove current flow through the valve.
3.
The anode voltage for each EL34 should be approximately 430V- 450V DC.
This is measured between ground and pin 3 of each EL34.
4.
The smaller tubes can also be checked top and bottom for bias voltages.
Final Assembly:
Disconnect from the mains.
The last two feet can be fitted to the bottom cover plate using M4 screws and
nuts. The holes in some of the cover plates will need drilling out to fit the M4 screw.
If using the larger feet, for the standard feet it will be fine.
Last of all the top cover plate must be fitted. The front of the panel tucks under the
front chassis panel and is secured by three M3 screws at the rear. If the top cover does
not tuck under the front panel the corners may need trimming off as shown in figure 8
below.
