Hot Rod Tweed Conversion for SF Bassman Head - The Blue Guitar
Hot Rod Tweed Conversion for SF Bassman Head - The Blue Guitar
Hot Rod Tweed Conversion for SF Bassman Head - The Blue Guitar
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<strong>Hot</strong> <strong>Rod</strong> <strong>Tweed</strong> <strong>Conversion</strong> <strong>for</strong> <strong>SF</strong> <strong>Bassman</strong> <strong>Head</strong><br />
B+5<br />
#2<br />
#1<br />
68k –<br />
120k *<br />
1.0M<br />
12AX7<br />
(EI)<br />
V3A<br />
33k<br />
1.0uF<br />
poly<br />
12AX7<br />
(EI)<br />
V1A<br />
33k<br />
1.0uF<br />
poly<br />
1k8<br />
1.67v<br />
1k8<br />
100k<br />
100k<br />
208v<br />
(213v)<br />
100k<br />
.022uF<br />
418P<br />
Volume<br />
1MA<br />
10uF<br />
+<br />
208v<br />
(213v)<br />
B+5<br />
+ 5uF<br />
.022uF<br />
418P<br />
1M<br />
Volume<br />
1MA<br />
51pf<br />
(SM)<br />
100k<br />
51pf<br />
(SM)<br />
100k<br />
1M<br />
10M<br />
Smooth Switch<br />
K1b<br />
22M<br />
.047uF<br />
1.34v<br />
1.0uF<br />
poly<br />
B+5<br />
195v<br />
(200v)<br />
100k<br />
.022uF<br />
418P<br />
V1B<br />
12AX7<br />
(EI)<br />
560pF (SM)<br />
470k<br />
470k **<br />
3.3M<br />
Ch Sw Relay<br />
12AX7WB<br />
(Sovtek)<br />
V2A<br />
K1a<br />
1.05v<br />
820R<br />
168v<br />
(173v)<br />
270pF<br />
100k<br />
100k<br />
** In lieu of Gain Switch<br />
use fixed resistor:<br />
150k Clean<br />
220k <strong>Blue</strong>s<br />
470k Crunch<br />
B+4<br />
304v<br />
(310v)<br />
V2B<br />
3.3uF<br />
poly<br />
110k<br />
Deep Switch<br />
680pF<br />
(SM)<br />
47k<br />
1M5<br />
.022uF<br />
418P<br />
.022uF<br />
418P<br />
330pF<br />
(SM)<br />
250kB<br />
Treble<br />
1MA<br />
Bass<br />
750pF<br />
(SM)<br />
25kB<br />
Middle<br />
470k<br />
470k<br />
Half-Power<br />
Switch (opt.)<br />
Master<br />
1MA<br />
100k<br />
To Output<br />
Section<br />
* 68k <strong>for</strong> BF specs<br />
120k <strong>for</strong> LP input<br />
Bright Switch<br />
Ch Sw Relay<br />
1k5<br />
3k3<br />
470k<br />
220k<br />
Gain<br />
Switch **<br />
Notes:<br />
Wiring <strong>for</strong> optional tube rectifier<br />
& switch shown on layout drawing<br />
Tube rectifier voltages in Black<br />
SS rectifier voltages in Red Italic<br />
418P = Orange Drop cap<br />
SM = Silver Mica cap<br />
Channel Switching variation A<br />
(Preamp section)<br />
Designed by Steve Ahola<br />
Rev.01-21-00
<strong>Hot</strong> <strong>Rod</strong> <strong>Tweed</strong> <strong>Conversion</strong> <strong>for</strong> <strong>SF</strong> <strong>Bassman</strong> <strong>Head</strong><br />
B+5<br />
#2<br />
#1<br />
68k –<br />
120k *<br />
1.0M<br />
12AX7<br />
(EI)<br />
V3A<br />
33k<br />
1.0uF<br />
poly<br />
12AX7<br />
(EI)<br />
V1A<br />
33k<br />
1.0uF<br />
poly<br />
1k8<br />
1.67v<br />
1k8<br />
100k<br />
100k<br />
208v<br />
(213v)<br />
100k<br />
.022uF<br />
418P<br />
Volume<br />
1MA<br />
10uF<br />
+<br />
208v<br />
(213v)<br />
B+5<br />
+ 5uF<br />
.022uF<br />
418P<br />
1M<br />
Volume<br />
1MA<br />
51pf<br />
(SM)<br />
100k<br />
51pf<br />
(SM)<br />
100k<br />
1M<br />
10M<br />
K1b<br />
Smooth Switch<br />
22M<br />
.047uF<br />
1.34v<br />
1.0uF<br />
poly<br />
B+5<br />
195v<br />
(200v)<br />
100k<br />
.022uF<br />
418P<br />
V1B<br />
12AX7<br />
(EI)<br />
560pF (SM)<br />
470k<br />
470k **<br />
3.3M<br />
Ch Sw Relay<br />
12AX7WB<br />
(Sovtek)<br />
V2A<br />
K1a<br />
1.05v<br />
820R<br />
168v<br />
(173v)<br />
270pF<br />
100k<br />
100k<br />
** In lieu of Gain Switch<br />
use fixed resistor:<br />
150k Clean<br />
220k <strong>Blue</strong>s<br />
470k Crunch<br />
B+4<br />
304v<br />
(310v)<br />
V2B<br />
3.3uF<br />
poly<br />
110k<br />
Deep Switch<br />
680pF<br />
(SM)<br />
47k<br />
1M5<br />
.022uF<br />
418P<br />
.022uF<br />
418P<br />
330pF<br />
(SM)<br />
250kB<br />
Treble<br />
1MA<br />
Bass<br />
750pF<br />
(SM)<br />
25kB<br />
Middle<br />
470k<br />
Half-Power<br />
Switch (opt.)<br />
470k<br />
Master<br />
1MA<br />
100k<br />
Note: Master Volume is<br />
essentially disabled in<br />
Clean mode.<br />
To Output<br />
Section<br />
* 68k <strong>for</strong> BF specs<br />
120k <strong>for</strong> LP input<br />
Bright Switch<br />
Ch Sw Relay<br />
1k5<br />
3k3<br />
470k<br />
220k<br />
Gain<br />
Switch **<br />
Notes:<br />
Wiring <strong>for</strong> optional tube rectifier<br />
& switch shown on layout drawing<br />
Tube rectifier voltages in Black<br />
SS rectifier voltages in Red Italic<br />
418P = Orange Drop cap<br />
SM = Silver Mica cap<br />
Channel Switching variation B<br />
(Preamp section)<br />
Designed by Steve Ahola<br />
Rev.01-21-00
<strong>Hot</strong> <strong>Rod</strong> <strong>Tweed</strong> <strong>Conversion</strong> <strong>for</strong> <strong>SF</strong> <strong>Bassman</strong> <strong>Head</strong><br />
B+5<br />
#2<br />
#1<br />
68k –<br />
120k *<br />
1.0M<br />
12AX7<br />
(EI)<br />
V3A<br />
33k<br />
1.0uF<br />
poly<br />
12AX7<br />
(EI)<br />
V1A<br />
33k<br />
1.0uF<br />
poly<br />
1k8<br />
1.67v<br />
1k8<br />
100k<br />
100k<br />
208v<br />
(213v)<br />
100k<br />
.022uF<br />
418P<br />
Volume<br />
1MA<br />
10uF<br />
+<br />
208v<br />
(213v)<br />
B+5<br />
+ 5uF<br />
.022uF<br />
418P<br />
1M<br />
Volume<br />
1MA<br />
51pf<br />
(SM)<br />
100k<br />
51pf<br />
(SM)<br />
100k<br />
1M<br />
10M<br />
K1b<br />
Smooth Switch<br />
22M<br />
.047uF<br />
1.34v<br />
1.0uF<br />
poly<br />
B+5<br />
195v<br />
(200v)<br />
100k<br />
.022uF<br />
418P<br />
V1B<br />
12AX7<br />
(EI)<br />
470k<br />
Ch Sw Relay<br />
560pF (SM)<br />
470k **<br />
3.3M<br />
12AX7WB<br />
(Sovtek)<br />
V2A<br />
K1a<br />
1.05v<br />
820R<br />
168v<br />
(173v)<br />
270pF<br />
100k<br />
100k<br />
** In lieu of Gain Switch<br />
use fixed resistor:<br />
150k Clean<br />
220k <strong>Blue</strong>s<br />
470k Crunch<br />
B+4<br />
304v<br />
(310v)<br />
V2B<br />
3.3uF<br />
poly<br />
110k<br />
Deep Switch<br />
680pF<br />
(SM)<br />
47k<br />
1M5<br />
.022uF<br />
418P<br />
.022uF<br />
418P<br />
330pF<br />
(SM)<br />
250kB<br />
Treble<br />
1MA<br />
Bass<br />
750pF<br />
(SM)<br />
25kB<br />
Middle<br />
470k<br />
Half-Power<br />
Switch (opt.)<br />
470k<br />
Master<br />
1MA<br />
100k<br />
Note: when Clean channel is selected<br />
highs will be boosted at low settings<br />
of Master Volume. [EXPERIMENTAL]<br />
To Output<br />
Section<br />
* 68k <strong>for</strong> BF specs<br />
120k <strong>for</strong> LP input<br />
Bright Switch<br />
Ch Sw Relay<br />
1k5<br />
3k3<br />
470k<br />
220k<br />
Gain<br />
Switch **<br />
Notes:<br />
Wiring <strong>for</strong> optional tube rectifier<br />
& switch shown on layout drawing<br />
Tube rectifier voltages in Black<br />
SS rectifier voltages in Red Italic<br />
418P = Orange Drop cap<br />
SM = Silver Mica cap<br />
Channel Switching variation C<br />
(Preamp section)<br />
Designed by Steve Ahola<br />
Rev.01-21-00
<strong>Hot</strong> <strong>Rod</strong> <strong>Tweed</strong> <strong>Conversion</strong> <strong>for</strong> <strong>SF</strong> <strong>Bassman</strong> <strong>Head</strong><br />
56k<br />
From<br />
Preamp<br />
4k7<br />
0.1uF<br />
418P<br />
.022uF<br />
418P<br />
10k<br />
0.1uF<br />
418P<br />
Presence<br />
25kB<br />
1M<br />
12AX7WA<br />
(NOS GE)<br />
V4A<br />
1M<br />
470R<br />
38.7v<br />
V4B<br />
100pF<br />
232v<br />
(238v)<br />
82k<br />
223v<br />
(229v)<br />
B+3<br />
100k<br />
.033uF<br />
418P<br />
.033uF<br />
418P<br />
Bias<br />
220k<br />
220k<br />
6L6GC<br />
(Svet)<br />
V6<br />
1500<br />
1500<br />
5<br />
V5<br />
6L6GC<br />
(Svet)<br />
5 4<br />
8<br />
8<br />
4<br />
3<br />
3<br />
B+2<br />
1k/5W<br />
1k/5W<br />
B+1<br />
Brown<br />
<strong>Blue</strong><br />
Ext Spkr<br />
Main Spkr<br />
4 ohms<br />
Polarity <strong>for</strong> OT shown<br />
<strong>for</strong> <strong>Bassman</strong> head built<br />
after 1965 using positive<br />
feedback loop.<br />
Black<br />
120vac<br />
Power<br />
White<br />
Power<br />
Switch<br />
2.0A SB<br />
Fuse<br />
100R<br />
100R<br />
Standby<br />
Switch<br />
100uF<br />
350v<br />
100uF<br />
350v<br />
To filaments<br />
& pilot lamp<br />
B+1<br />
B+2 B+3 B+4 B+5<br />
439vdc 438vdc 350vdc 303vdc 287vdc<br />
(452vdc) (451vdc) (360vdc) (313vdc) (295vdc)<br />
Choke<br />
220k/1W<br />
220k/1W<br />
470R / 1W<br />
20uF<br />
500v<br />
100uF<br />
100v<br />
12k/2W 10k/2W 10k/2W<br />
20uF<br />
500v<br />
20uF<br />
500v<br />
Bias Adj<br />
10kB<br />
15k<br />
20uF<br />
500v<br />
Bias<br />
-48.7v <strong>for</strong><br />
~32.5mA<br />
(6L6GC's)<br />
0.22uF<br />
630v<br />
(opt.)<br />
Notes:<br />
Wiring <strong>for</strong> optional tube rectifier<br />
& switch shown on layout drawing<br />
Tube rectifier voltages in Black<br />
SS rectifier voltages in Red Italic<br />
418P = Orange Drop cap<br />
SM = Silver Mica cap<br />
Channel Switching variation<br />
(Power amp section)<br />
Designed by Steve Ahola<br />
Rev.01-21-00
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