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Gb 100 base amp
- Thread starter Staybolt
- Start date
I had one that the receive preamp didn't work, but the amp worked well. Gave it away to a new operator who bought a Melaka from me.
Other than that I don't know much about them.
MRF455 X 2
Other than that I don't know much about them.
MRF455 X 2
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The one I had worked except for the receive pre-amp. I didn't know how to repair it although I think I did at some point replace some transistors. I'm not a tech or anything, and I have several other amps, so I left it as is and it went with the Melaka I sold with that understanding.
The Reverend BDW, grey electronics.
The power supply is not regulated, so it floats at about 19 volts unloaded then pulls down when keyed.
No bias so it's going to be iffy on SSB, the switch on the front just adds a delay to the relay.
73
Jeff
The power supply is not regulated, so it floats at about 19 volts unloaded then pulls down when keyed.
No bias so it's going to be iffy on SSB, the switch on the front just adds a delay to the relay.
73
Jeff
This amplifier is famous for blowing out the RF power transistors. The high unregulated voltage is the cause. Most of them we have seen used a toroid power transformer, rather than the conventional one in the pics here.
As for "iffy" on sideband, I would characterize it more like a mouthful of sandpaper. The designer did NOT have sideband in mind, and didn't spend the extra money to make it happen. When a customer asks about the switch marked "SSB" I tell him that it's just a fig leaf over the private parts.
The dominant failure mode seemed to happen when you unkey. The unregulated power supply voltage would jump up, and a RF transistor would break down. Turns out getting them hot from a normal load reduces the voltage needed to make them break down and fail.
We tamed them by adding a 30-Amp automotive relay between the RF transistors and the power supply. The new relay gets keyed with the original relay. The unregulated power supply drops to a safe level when the transistors are turned on and drawing load current. The added relay just removes power from the RF transistors until you key the mike, and the transistors draw down the voltage. Removing power from the expensive transistors when you unkey fixed this hazard.
73