SB-230 Retrofit Using the GI-7B
by K4POZ September - October, 2006

Please note: This was an early effort at retrofitting the SB-230 amplifier. Since this particular amp was worked on, many lessons have been learned. The first is that the power supply in the SB-230 is not capable of supporting two tubes with any improvement in operation or power. Secon is that mounting the tube vertical creates a space problem that can only be delt with by moving the RF sub chassis forward. For these reasons we do not recommend following these pictures to do your retrofit. Instead, look at the pictures of the single tube SB-230 with the tube mounted on the right side wall.

1
Front Panel

2
Rear Deck before blower cutout.

3
Before moving chassis forward.

4
Deck removed, layout started

5
Deck moved forward 1 inch

6
Another layout view

7
Sockets, rear view showing filament choke.

8
Sockets in place, fan cutout covered with copper gutter screen, blower shock mounted.

9
Old plate choke shown above with new plate choke shown below.

10
New plate choke

11
Plate choke end

12
RF Deck. Note the plexiglas air dam between the tubes and the tank circuit. The resistive input pad is in the upper right corner of the chassis as viewed here

13

14
Left view. You can see the bias board above and left of the power transformer.

15
Bias board mounted

16
Warming up


17
Socket wiring
.
18
.
19
.
20