Section 2
PREPARING THE ETO 91ß FOR OPERATION
Transformer Installation (See Figures 2-4)
Remove the amplifier top cover to install the transformer. Only one possible transformer
orientation allows mating all its connectors without straining leads. Lift the transformer high
enough to dear the right side chassis lip and move it sideways into the chassis. USE CAU
TION! PROCEED SLOWLY to avoid damaging wires or components. From underneath,
insert the supplied bolts with washers through the clearance holes in the chassis and into the
nuts in the transformer base. CAUTION! Mate transformer connectors carefully and gently
to insure that all connector pins engage correctly and fully.
Inspection of Tubes & Chimneys
While the top cover is removed, make sure tubes are firmly seated in their sockets, rubber
exhaust chimneys are fully and correctly installed, and anode connectors are tightly clamped
to tubes.
The silicone rubber chimneys installed on the 4CX800A/ GU74b tubes are absolutely essential
parts of the cooling system. Make sure the chimneys are straight and fully installed so that
the bottom of each chimney is firmly against the tube deck and completely covers the airflow
openings in the deck. Tube cooling air must exit only through the tube anode fins; it must not
be allowed to escape outside them. Failure to ensure proper cooling airflow may result in
tube damage or destruction which is not covered under warranty.
AC Primary Connections & Amplifier Grounding
Primary voltage taps are selected at the terminal strip numbered "1" to "7" and located on
the chassis center divider, left of and above the transformer. Connect the two wires labeled
"A" and "B" for the line voltage to be used, as shown in the following table. The two short
jumper wires supplied are not used on 200-250V, but must be connected as shown for opera
tion on 100-120V mains.
PRIMARY
"A" to terminal
4 (factory setting)
"B " to terminal
Tumpers
Not used for
190 to 250V
230-250V
210-230V
190-210V
110-130V
90-110V
4
5
4
5
2
3
3
6
6
operation
1 -> 2,6 -> 7
1 -> 3,6 -> 7
Power Cord Connections — WARNING!
To avoid hazard of potentially fatal electric shock and/or severe damage to the ETO 91fi
and other equipment, always use an AC plug which is appropriate for the primary mains
voltage, current rating and configuration. NEVER use 120V-type plugs and power recep-
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