Williamson 202-20 Schematic

R

26

0Ω

C

10

AOT

C

8.2nF

in

polystyrene

R

1

1MΩ

0.5W

R

33kΩ

1W

2

V

a a

310-320V

R

3

47kΩ

2W

85-105V

ECC81

1

2V

R

4

220Ω

0.5W

C

47µF

500V

310-320V

1

R

22kΩ

1W

R

22kΩ

1W

6

7

V

a a

C

2

22kΩ

C

*

200-210V

ECC81

87-107V

*

R

5

1W

C

2

47-100µF

500V

C

220nF

630V

V3+V

ECC81

170-180V

3

V

R

8

470kΩ

0.5W

R

9

470kΩ

0.5W

a a

R

10

180Ω 0.5W

a a

V

C

4

220nF

630V

Items marked in orange are changes

from the original schematic

C*= 1.0µF — 4.7µF Polypropylene

(MKP) bypass capacitor which may

improve high frequency definition!

4

3

4

2V

170-180V

C

47-100µF

500V

R

11

47kΩ

2W

R

13

47kΩ

2W

420 - 440V

5

C

*

C

6

220nF

630V

R

14

470kΩ

0.5W

R

19

470kΩ

0.5W

C

7

220nF

630V

all other resistors 5%

100Ω 1W

1kΩ 0.5W

100Ω 1W

R

100Ω

2W

100Ω 1W

1kΩ 0.5W

R4 and R

R

R

R

17

R

R

R

100Ω 1W

25

CH

1

30H > 20mA

( Sowter 8609 )

R

1kΩ 1W

CH

1

23

15

16

R

21

100Ω 2W

18

20

24

1%

V

5

a a

R

22

150Ω 3W

a a

V

6

C

8

68-100µF

500V

440 - 460V

KT66

35-40V

KT66

10H > 150mA

( Sowter CA15 )

220nF 630V MKT

for 50Hz mains

180nF 630V MKT

for 60Hz mains

T

2

C

*

CH

2

C

hum

8-22µF

630V MKT

( Sowter 8950

set to 15Ω )

Output

R

15

1.2kΩ√Z

4.7kΩ 0.5W

C

9

out

0V

0V0V

Note: This schematic
contains changes from the
original, refer to: www.dc-

daylight.ltd.uk for original

values.

T

1

5V

@ 3A

V

7

425V

@ 150mA

425V

@ 150mA

a

6.3V @ 4A

a

F

315mA AS

1

a.c.

mains

in

This link may be

replaced with

<4.7Ω 1W resistor

to prevent hum

loops

L

N

E

The Williamson Amplifier “new version”

The Williamson Amplifier “new version”

from Wireless World August 1949 p. 282

from Wireless World August 1949 p. 282

Redrawn 1996 by Keith Snook

Redrawn 1996 by Keith Snook

d.c. ~ daylight ltd

d.c. ~ daylight ltd

.

.