"Schematic:

http://elektrotanya.com/files/forum/...eplacement.jpg "

WOW ! Now that might just save the day. Thanks. I notice a dot RO in the picture there, does that mean Romania ? I've been told by some from across the pond that alot of parts are very hard to get, it's not like the US. They have had to become more resourceful as a result.

So it pretty much boils down to do this unless I can scare up a jubnker with the IC. This looks highly doable. the only thing now is the selection of the MOSFETs. Voltage, current and frequency response are obvious, the only question is gain.

It's obvious that the 1K resistors set the gain to some extent, but the highest gain possible is not always best in tis type of application. Or is it ? a thousand ohms isn't much, maybe the highest gain within reason would be best. If you want to make a suggestion I am highly suggestable. The main thing I know is to get devices that will work in the linear region. That will probably mean looking at some datasheets because most linear applications I've seen are either audio or video amps and neither of them are going to have the frequaency response for this. At least not necessarily. Also, surely the devices exist, it's just that I haven't seen them in the stuff I've worked on.

I actually thought of a retrofit myself, but I was going to stick more to the original, using bipolar. Of course that was not thiknking outside the box in a way - we only need this to do a certain thing, if FETs work, use them and make it easier. I would guess devices like that were not available when they built that unit, but they are now !

:-)