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Filament Transformer

Filament transformer

This 22 pound big-boy has a turns ratio of 30:1. With 225 VAC 60 Hz on the primary, the secondary will have 7.5 VAC at 75 amps. The secondary is center tapped to prevent cathode current from saturating the core, and also inducing 60 Hz hum into the RF. The secondary is isolated to 1500 VDC for use with a grounded screen 4CX10000D tetrode which has the filament circuit at -1250 VDC to the chassis.

This transformer is rated from 50 Hz through 400 Hz, so at 60 HZ, the primary can be boosted up to 270 VAC without saturating the core to give 9.0 VAC on the secondary for tubes that use that voltage. The 30 VAC Variac in another box on this page is for adjusting the filament voltage and works to boost the line voltage up to 270 VAC. This transformer will also handle 5.0 VAC at 90 Amps with 130 VAC on the primary.

Two sold, I now have 2 of these transformers left.

3 Phase Transformer

3 phase Power Transformer

The primary is 208 VAC, 50/60 Hz, 3 phase, and the secondary after rectification yields 250 VDC. It came from a 32,000 Watt sonar amplifier. The weight is about 250 pounds.

Variac Powerstat

30 VAC Variac

This is a Powerstat brand similiar to Variac. The primary is 120/240 VAC and the secondary is 0 - 30 VAC. The transformer is about 1 KVA, and was designed to feed the primary of the filament transformer for a 4CX10000D tetrode to fine-adjust the voltage. This Variac is plenty big enough to vary the plate and filament supplies of any amateur amplifier.

Sold 2, have 2 units left.

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