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These notes are only intended for use by an engineer qualified to work with high voltage triodes like the 845/805. Owners
should refer any problems to a dealer or service agent.
The amplifier may be inverted by supporting the transformers on non abrasive surface (e.g. dense foam, books etc) which
allows space between the KT150’s and the work surface.
Safety
Before removing base disconnect the power cord. Always allow 20 minutes for the HT to discharge, or measure before
proceeding. Use a bleed resistor of around 5-10KΩ will speed this up, and check that the HT voltage has discharged.
Amplifier dead.
Check the 20mm mains fuse in the IEC socket at rear of the amplifier, if dead there is a spare included. Or the fuse in the plug
(if applicable). If not either check in-line power switch fuse adjacent to IEC socket.
Amplifier lit but not working.
There is a 500ma HT fuse located on the chassis, with spares attached to the base. If the fuse blows again a VARIAC or
variable transformer will be useful to operate the amplifier on reduced power in order the trace the fault or overload.
Make sure the bias for the KT150’s is correct. If the AC fuse is blowing with the HT fuse disconnected suspect the bridge
rectifier or power supply.
Also check that the 6SL7/6SN7 6.3v supply is working.
230v to 115v Conversion.
Take the precautions as above. It is necessary to change the primary power windings from series to parallel. Remove either AC
lead from the bridge rectifier and join it to the other terminal. The “centre” tap are the two leads that will be found joined
together. Replace with these two and solder to the first terminal. A larger value AC fuse will be needed in the IEC socket.
115v to 230v Conversion.
This is changing the two primary windings to series.
Remove either pair of AC leads from an AC input to the bridge rectifier. Join together and insulate. The other pair of AC leads
should be separated and soldered to each AC input of the bridge rectifier. A lower value AC fuse will be needed in the IEC
socket.
