The Brimistor (Brimar Resistor)

14-10-65 Brimistor added.

Above, serial no. 6023 - the brimistor can be seen at the front of the chassis on two standoffs to the right of the mains transformer. For further pictures, .

Serial no. 4282 - no brimistor - and no holes for the standoffs or the feed-through for the underchassis wiring. Pot codes for this amp are "GM" = July 1965. For further pictures see .

The Brimistor was added by Vox to solid state rectified AC50s (and AC100s) as a means of delaying the inrush current when the amp was first switched on - an attempt to mimick the "slow start" provided by the GZ34 valve rectifier - the idea being that the heaters of the output valves had time to warm up before the rest of the circuit rose to operating levels.

A further hope may have been that the brimistor would protect the main filter capacitors from higher currents when AC50s were used in America. The American market was a large one.

The type of brimistor adopted was the "CZ4", the highest rated that Brimar produced.

Above, an extract from a Brimar brochure of the early 1960s. The full text .

Implentation evidently ran from around the date registered on the schematic until the end of the JMI in early 1968.

Whether the brimistor really worked as intended is a moot point - but the idea at any rate was an ingenious one.