Yaesu FT-227-R Memorizer
Reviving an old work horse
Being new to the world of Amateur Radio discoveries run rampant. I was milling around at a local HamFest (only the second one I've attended) and saw the words "Inop - Parts only" written on masking tape on the top of an obviously old radio. (As it turned out, it's so old that it was made when I graduated from High School!)
After picking it up and trying to figure out what it was, the guy behind the table says, "I think I've got the manual and schematic for that."
My salivary glands started to tingle -- It's the combination of "Inop" and schematic that does that to me.
I spent the next week discovering that this FT-227 was "leading-edge technology" in it's time and still has a cult following. I was able to browse up all sorts of info regarding modifications and such. Here's a few links...FT-227-R Links
The first thing I liked about this radio is that it was obviously meant to be worked on, the way that the PLL board flips up without having to remove any wires. Like the hood of a car, but unlike most modern cars it's simple, straight forward and everything is accessible...no emission control crap. The first thing I found wrong was some cracks in the circuit board around one of the screw mounts. It had obviously been dropped. I bridged the broken traces with wires and solder and it powered on.
|The receiver worked, but no transmit. I was immediately suspect of the relay. The schematic showed that it is used to switch the 8 volt power supply back and forth from receive to transmit. Sure enough, the voltage at the output of the relay was low on the RX side and non-existent on the TX contact. Rather than fuss with cleaning or replacing it I figured I'd come up with a solid state version to eliminate the possibility of the next one going out in the next twenty five years. Here's what I came up with. FT-227-R Solid State Relay|
After getting the TX/RX power supply problem taken care of there was still no output. TP1 showed the proper voltage and responded when I tweaked T201. Out came my scope. The FM signal was getting to the initial two transistors in the PA stage but no further. The last driver (Q207) before the final amp (Q208) was open. It's a 2SC730 RF driver. I had a 2N3866 out of an old Heathkit HW-202 that is similar enough. (The HW-202 also uses an equivalent output device as the FT-227, so I've got a backup.) Replaced the driver and Voila! RF output.
A little tweaking of the caps and the most I've been able to get out of it so far is 6+ Watts. As far as I can tell the 2N3866 has the same gain factor as the C730. I'm not quite sure why I'm not getting the full 10. Any ideas? Not to worry, it's enough to get to our local repeater and/or drive an amp.
|I've already moved on from that problem to working on a CTCSS tone board. I need something to fill up this empty space. FT-227-R PL Tone Board|