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P a g e
any signals may interfere with the Bias settings. Switch t
he amp ‘ON’ using the rear
illuminated mains switch and then after 60 seconds, switch the front panel toggle
from PREHEAT, (centre position) to HIGH, (top position).
Now put the black meter probe, (-ve) into the Black centre GND Bias socket and the
red meter probe, (+ve) into the RED (V4-V7) Bias socket. Using a small flat blade
screwdriver in the Bias adjustment POT, turn this so you get 5.6Vdc on the
mult/-0.25V.
We are measuring this voltage across a 47 Ohm resistor so Ohm law, V=IxR (Voltage
= Current x Resistance) gives us Current = 5.6V/47Ohms which = 120mA for all 4
valves. Dividing this by 4 gives us a maximum Bias current of 30mA per valve.
SPEAKER OUTPUTS
PLEASE NOTE: The lightning flash with arrowhead symbol, within an equilateral
triangle, is intended to alert the user to the
presence of uninsulated ‘dangerous
voltage’ within the product’s enclosure that may be of sufficient magnitude to
constitute a risk of electric shock. Terminals labelled as “Speaker Outputs” must be
connected to a speaker cabinet of the designated load rating using an un-shielded
two conductor cable for speaker use at all times during operation. Never use a
guitar cable to connect the amplifier to a speaker as this presents the amplifier with
a ‘capacitive load’. This can cause instability or oscillation wh
ich may seriously
damage valves and/or the expensive output transformer.
Always ensure a speaker is connected to the amplifier before powering up or
damage to the output transformer may result. Never unplug a speaker when the
amplifier is ON as this is even more likely to damage the transformer and the
output valves.
The output transformer in the VC35 has 2 separate secondary windings; a 16 Ohm
and an 8 Ohm. This makes it easy to connect different combinations of speakers.
There are three speaker output jacks: 2 x 8 Ohms, (wired in parallel) and 1 x 16
ohms.
Here are the possible combinations:
1.
For a single 8 Ohm cabinet, use either of the 8 Ohm sockets.
2.
For a single 16 Ohm cabinet, use the 16 Ohm socket.
3.
For a pair of 16 Ohm cabinets, use both of the 8 Ohm sockets.
It is possible to use a pair of 8 Ohm cabinets with the VC35 but a special series
lead needs to be used.
