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Drake Converter



Good Evening to All,

I'm working on a Drake converter that got flooded.  When I took the cover
off there was standing water inside.  The PCB track to the IF connector
had been burned (or corroded) away and there was extensive corrosion on
the PCB, most of it in the P/S section.  I was able to clean it up pretty
well and now the voltages around the rf amp look OK so I think that part
will work if I can get the oscillator going.  I managed to get the 8 mhz
oscillator working by replacing the crystal trimmer with a 5 pf fixed
capacitor but I still have no mixer injection.  I think I have found the
culprit but I don't know what it is!  There are two 4 terminal SM devices
between the oscillator section and the mixer with "R27" stamped on the
package.  The device that is about half way up the oscillator injection
trace to the mixer does not appear to be working.  I think these devices
are bipolar but they could be some form of FET.  They seem to have dual
emitter (or source) connections.  The one under the small shield appears
to be a follower (source or emitter) and I think the other is a straight
amplifier.  The follower has 10 volts on the collector (or drain), 2.6
volts on the base (or gate) and 2 volts on the emitter (or source).  The
other one has 10 volts on the collector (or drain), 3 volt on the base
(or gate) and zero volts on the emitter (or source).  The level of the
voltages on the one that's working (at least as far as DC is concerned)
leads me to believe that these are bipolar devices but I haven't a clue
about what to replace them with.  Can anyone offer any help?  Even an
educated guess would help.

Thanks,

73 - de Jess - W4MVB
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