Hi all, I acquired an older linear, it's labeled GOLD 150 and I have also seen them labeled DYNAMO GOLD 150. It's a nice little solid state amp and works very well except when you turn on the preamp the receive drops out so I am hoping someone is familiar with the amp and perhaps someone has a schematic and can tell me what component(s) may be bad. Thanks for any help. Adam
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Help with preamp in Gold 150 linear amplifier
- Thread starter Adamf
- Start date
Not familiar with this brand and model, but preamps are not so different from one brand to the next. They're not built to tolerate any significant surge energy. When you key the mike on AM, there is a small delay for the relay to respond and unhook the preamp from the full power of your transmitter. For a short instant the preamp. a circuit meant to amplify nanoWatts is getting fed a billion times that much power, coming up into its output the wrong way. But the relay responds after ten or so milliseconds, making this a short burst of surge current. You'll usually find a protection diode that keeps the preamp transistor from blowing out so long as the surge is brief.
But sooner or later someone tries to use sideband with the preamp turned on . That sideband switch causes the relay to slow down. And before long that surge of RF when you key up lasts long enough to blow out the preamp transistor and its protection diode, both.
Feel free to test parts in the preamp and replace the blown ones.
But don't expect the preamp to last terribly long. Circuits that would make it last longer cost money and won't make it sell any better. As a result they get left out.
73
But sooner or later someone tries to use sideband with the preamp turned on . That sideband switch causes the relay to slow down. And before long that surge of RF when you key up lasts long enough to blow out the preamp transistor and its protection diode, both.
Feel free to test parts in the preamp and replace the blown ones.
But don't expect the preamp to last terribly long. Circuits that would make it last longer cost money and won't make it sell any better. As a result they get left out.
73
