In February 2013 I start with my second linear with two GI7B. I was finish in May 2013.
I made experiments with microwave oven transformers. The problem is the overheating of this transformers. This transformers was build for impulse usage, and not for a permanent use. So I find a circuit in the internet from a other OM. He control this transformer with a LM393 IC. But you need a big transformer from a Moulinex Microwave oven.
You can make 800 Watts with this linear on 80m SSB. It works fine for a long time.
Here you can download the schematics for the power supply: netzteil-2GI7.sch
Here you can download the schematics for the RF part: HF Teil. 2GI7
It works with a microwave oven transformer, but the power supply make a noise like a beating heard, when he is regulated the voltage 🙂
I sold this linear, after a longer usage.