Mirage A1015 Preamp?? - Elmers Forum at eHam.net

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Mirage A1015 Preamp??	Reply
by W5GNB on July 4, 2008	Mail this to a friend!
I have an old Mirage A1015 Six meter amplifier that works just fine except that the RX preamp is out. I have the replacement transistor for it but am not sure of the position of which to place it on the board. I do not have a schematic or any photo data on the unit so I didn't want to just solder in the new transistor without knowing at least how it should be placed on the board. I have been unable to obtain any schematic for the unit and even MFJ has not been too cooperative. I have heard that the RX amp is really not worth fixing anyway but since I have the part, I might as well give it a try. Any ideas???? Gary

RE: Mirage A1015 Preamp??	Reply
by KB1GTX on July 4, 2008	Mail this to a friend!
Does the transistor have four leads, if it does the lead with a cut angle will be the colector.

RE: Mirage A1015 Preamp??	Reply
by K0BG on July 4, 2008	Mail this to a friend!
Although they operate on different frequencies, all of the Mirage VHF amps are more or less the same. There is only one FET on the board, all of the rest as planers. Depending on the age, the FET is either 4 or 3 pins. If it is 4 pins, it should be glaringly evident where it "goes". If it is 3 pins, look at the nomenclature on the transistor itself. Or, you can follow the traces from the Preamp power switch, through the source choke, directly to the FET's location. Personally, I have never had MFJ refuse a request for a schematic. As long as your FCC database address is the address you're requesting it be sent to, there will not be a problem. By the way, if you want the new part to last, don't use RF keying. Alan, KØBG www.k0bg.com

RE: Mirage A1015 Preamp??	Reply
by WB2WIK on July 4, 2008	Mail this to a friend!
The A1015's preamp is pretty worthless, I wouldn't spend a minute replacing it. I have the A1015"G" (GaAsFET preamp) and it's also worthless. It has a LOT of gain and makes the S meter read about 20 dB higher. But that means nothing regarding sensitivity or the ability to hear a weak signal. Preamp "in" or "out," other than the S meter reading, there's no difference. The reason I wouldn't replace it is it's likely to blow again: The T-R bypass relay circuits are not properly sequenced to prevent damage. WB2WIK/6

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