Notes on Power Transformer T7

T1 is the power transformer. There at least three varieties:

1. The earliest version had some terminals and some wire connections.
2. A limited edition version had a large boxy case without the Hallicrafters metal cover. It had all terminals.
3. The most common and last version had all terminals and a metal box with the Hallicrafters logo to protect the top.

Type One

Part number 52-033

	Pins/wires

	6.3 Filament: pins 3 and 11
	5.0 Filament: leads
	Primary: pins 5 and 9
	High voltage: leads

	Ohm meter reading between pins/wires:

	3-11     0.07 ohm
	5V leads 0.08 ohm
	High voltage: leads, 33 ohms end to centertap, 39 ohms other end to centertap

	

Type Two

My one example of this part is in a working radio (#5)

Type Three

Part number 52B033.
This type seems identical to type one with the addition of the additional terminals in place of wires.

	Pins/wires

	Primary: pins 5 and 9
	5.0 Filament: pins 2 and 4
	6.3 Filament: pins 3 and 11
	High voltage: pins 8, 10 (center tap), and 12

	Ohm meter reading between pins:

	2-4      2.1 ohm
	8-12     71.8 ohm
	8-10     35.4 ohm
	10-12    38.4 ohm
	3-11     2.1 ohm
	5-9      4.0 ohm
	7, 6     no connection
	

Page: /T7_pwr/T7.shtml

Last modified: Thursday, 7 May 2026