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I bought a used Green Heron RT-21 from Stan a while back. After receiving it, I did a power-up test and it seemed to work. Some time later I decided to install the RT-21 into my setup and the first thing I tried to do was use the RS-232 port to upgrade the firmware. Whereupon, I discovered the RS-232 port is dead.

So, I opened up the case to do some trouble shooting and immediately I found that someone had been trying to solder parts onto the main board - connectors are melted, a transistor had been swapped out, and a trace going to the transistor is torn up from the pcb.

I checked the V+/V- pins on the RS-232 IC (MAX232ECN) and I found they are dead (should be +/-8.5v). Clearly, someone has fried this unit and now I'm stuck with it.

Do not do business with Stan King W4KR - apparently, he wrecks his equipment, performs incompetent repair work, and dumps half-dead equipment onto the used market (for a like-new price).

I replaced the MAX232 part and the port is still dead. It turns out that the serial pins of the CPU are also smoked. Now I get to replace the CPU, as well.

The saga continues...

I replaced the main CPU. It brought the serial port back to life. The RT-21 unit seems to be mostly working.

However, now I see the display locks up after a while. I talked to Jeff at GHE (he's been very generous with his support) and we've decided I'll need to replace the display board, or at least the auxiliary CPU on the display board. I'll start with the auxiliary CPU.

Guys, keep your distance from W4KR - Stan King.

OK, I'm getting real close now. Jeff at GHE sent me a display-CPU. I removed the old one and soldered the new one onto the display board. Voila! The display seems to be working now. I can finally use this unit - keeping in mind there may be other silicon parts that are suspect. We'll see.

Gee, thanks Stan!