18
In order my preferred places would be Fig. 28 or 29 and lastly just to chassis depending on the
board’s generation.
1.) Between a +24V pick point and the filament center tap or filament lead (shown below in fig
28 and 29)
2). Near the filament CT (white lead) that is accessible, such as
on the Zener’s
3.) Between a filament pin and ground on a tube socket
This would be a suitable alternative resisto
r location on the Zener’s prepped for installation
when the resistor is not in the preferred location. (Remember one Zener for amplifiers that
have a string of bias diodes.)
Figure 27 Zener's with 100k (avoid dropping back panel or early Gen I board)
There was an intention in revised boards to 24 to +30 Vdc as a standby bias offset
reference. There is a pick point for this reference on the later boards. The 100K 2W resistor
connects between that 24+ point and any nearby easiest accessible point of the filament
winding.
The tap point I provided for bias or accessory use can be identified by looking for two small
rectifier diodes near one of two small electrolytic capacitors. If you have the back panel down
Warning:
Ameritron has some transformers that are out-of-spec on the LV control
winding. The LV control winding was specified to produce 12-14 Vdc output from a
capacitor input filter system. Due to transformer errors, so later unit can have DC
voltages almost 50% beyond the specified voltage. I am trying to get an idea how
many bad transformers are out in the field. Please contact me if you have one.
