Drake R7 Mods

Discussion in 'Radio Circuits, Repair & Performance' started by AA7BQ, Sep 12, 2004.

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  1. AA7BQ

    AA7BQ QRZ Founder Administrator QRZ Page

    Drake R7 Modifications

    1. 24V & -5V multivibrator PS PCB ["19" board] was fed from the +10V regulated supply line on some models. Reconnecting the input to this board to the +13.8V supply removes some burden & switching transients from the +10V supply improving voltage regulation.
    2. Remove Q1301 from the RF filter-switch ["13"] board & place a jumper in the holes formerly occupied by its emitter & collector leads. This allows operation of preamp [Q1302] on bands 1, 2, & 3. Preamp is still controlled by the preamp enable switch.
    3. Replace incandescent RIT indicator lamp w/a red T1 or rectangular LED in series w/a 1K ohm, 1/4-watt resistor to end bulb burnouts here.
    4. Remove the no. 53 pilot lamps from the analog tuning dial & S-meter, break the glass bulbs & remove the filaments. Solder a high intensity white T1 3/4 LED in place of each filament w/the cathode connected to the shell of the lamp base & the anode to the center terminal. I left the lamp sockets wired in parallel & connected a 200 ohm, 10-watt resistor in series w/their +13.8 supply line. Although this resistor was much heavier than necessary it had the advantage of being able to mount to the R7 chassis. I tried soldering 1/2 watt series resistors to each of the old no. 53 lamp bases first but found they got too hot & made the new LED/resistor "lamp" assemblies too large so I removed them from the bases & fed them both w/the 200 ohm resistor from my junk box. In reality, anything 180-200 ohms, over 2 watts just to be safe will work here.
    5. This last mod. I haven't tried yet. It consists of outputting the R7's 3rd IF to an upconverter which changes it to 455 KHz., then this signal is buffered & fed to a Sherwood Engineering SE-3 MK III D AM PLL [phase locked loop] detector which is claimed to outperform Drake's PLL detector. This is an outboard unit & sells for about $744 w/all three components plus S&H. If Sherwood connects the 3rd IF output line there's an additional $45 charge. If you're interested more info can be found at: www.sherweng.com.

    Drawings showing these changes are available, for more info e-mail me at wireaddict1@aol.com.
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