So I bought an old uniden has a knob on the back to control variable power. Inside was a piece of round plastic with 4 wires going on to it so I warmed it up and started slowly removing layer after layer it appears to be 5 diodes in a series. With 2 wires hooked to each end. Anyone seen a mod like this before? Giving my eyes a rest. Then going to continue trying to get to the values.
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Uniden Grant variable power?
- Thread starter Redbeard190
- Start date
yep, it was known as the "supermod".
its a way to lower the deadkey while keeping the max modulation swing.
you should see two wires coming from the kit that go into the PC board where a diode was. its a rectifier diode.
the idea is that each additional diode put in series with this diode lowers the voltage to the driver and final by .7 volts, thereby lowering the deadkey.
once the diodes are forward biased by going into TX mode, the modulation is put through at a 1:1 ratio so you get max forward swing.
LC
PS- it looks like both the driver and final bias controls have been maxed out or possibly turned all the way down. these need to be set properly to avoid blowing out the power transistors.
its a way to lower the deadkey while keeping the max modulation swing.
you should see two wires coming from the kit that go into the PC board where a diode was. its a rectifier diode.
the idea is that each additional diode put in series with this diode lowers the voltage to the driver and final by .7 volts, thereby lowering the deadkey.
once the diodes are forward biased by going into TX mode, the modulation is put through at a 1:1 ratio so you get max forward swing.
LC
PS- it looks like both the driver and final bias controls have been maxed out or possibly turned all the way down. these need to be set properly to avoid blowing out the power transistors.
Thank you very much for the reply. Yes I was looking at the way it's wired in. It kinda shocked me when I seen one of the wires coming from the on/off-volume knob. Good eye on bias will definitely take care of this radio. The man who owned it is now a silent key.