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Re: Fried Drake downconverter fix?



At 12:28 PM 6/1/2003 +0930, vk5akj@corprit.net wrote:
>On 31 May 2003 at 12:11, Ken Swaggart wrote:
>
>> Well, I finally did it. Transmitted 50 Watts into my Drake 2880 this
>> morning! Anyone have a web page with fixes for it? (Spare has been
installed
>> until the next smart move by the chief op.)
>> 
>> 73,
>> Ken, W7KKE
>> 
>Join the club.
>For circuit and info try
> 
>http://www.ghengineering.co.uk/g8ubn/drake/Drake1.jpg 
>
>He was an absolute goldmine for me, the transistors you most likey 
>need are a darlington pair nec2SC3357.
>No longer available for me, I used Phillips BFQ19 works 100%.
>The problem I had was the darlington config had great strife in 
>finding the burnt out one till got onto the above url.
>Re using an unmodified drake at 123mhz and the FT847 CAREFUL
>If you come out of satellite mode and forget and/or have 144-147 mhz 
>in memory and press the rotten mox button instead of the power button 
>POOF !
>
>moral get some spare transistors you WILL one day cook the duck.
>73 all ron vk5akj (acheyJ)

For FT-847 users: even a better move is to make the relatively simple
DL1MEA mods to isolate the receiver antenna.  I did that on my FT-847 and
no longer need to worry about transmitting into my Drake.

The top cover comes off with 5-screws and the "speaker" cover with
12-screws.  The 144 and 432 circuitry is readily accessible right on top.
I chose to solder RG-174 coax jumpers directly to the pcb connectors after
removing the internal coax jumpers (if one can find the special male coax
connectors used by Yaesu, you could make them up for the RG-174 and not do
any soldering).  The 144-Rx coax line goes to a flange-mount sma mounted in
the ventilation slots on the back panel (drilling two 2-56 holes)(if you
can find bulkhead hole-mount sma's then no drilling is needed)(or run the
RG-174 thru the vent and directly to the Drake).  A RG-58 sma to BNC cable
connects to either my EME preamp output or the Drake power inserter.    

I use another RG-174 jumper, with BNC connector, soldered to the T/R pcb in
the radio to restore the Rx for ordinary transceiver use.  Eventually the
144 Rx sma connection will route thru a surplus BNC 1P6T relay to feed my
several 144 MHz IF xtvr receive systems and position #6 on the relay will
reconnect the T/R circuit.  For now, I manualy connect either the EME,
Drake, or restoration line as needed.  BUT....Never have to worry again
about hitting the MOX, being in Sat-MODE, etc.

73, Ed - AL7EB

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