Hi,
I'm not sure that this is the appropriate thread for this, but here goes.
I've got an LG OS-5020 oscilloscope that I recently purchased (my first scope). It apparently had a blown channel 2. I did a little poking around and decided to swap what I'm pretty sure is a JFET between channels 1 and 2. After swapping this component (labeled "304 E7G" - photo attached), channel 1 worked and channel 2 didn't. The channel that doesn't work doesn't have a trace at all. I don't have a schematic, but there is one available for a similar scope, the OS-9020G. This schematic lists a part "2SK304E" and is the only FET in the parts list.
It doesn't seem like this part is available anymore, so I bought an ON Semi "MFP4393" which seemed to be fairly similar. The pinouts are different, so I had to do some creative bending of the legs to make sure the S/G/D pins are in the right holes (marked on the circuit board even, which is nice). There's no change with this part in place; the failed channel still doesn't display. And yes, I checked and the legs weren't shorted against each other. I even tried a MOSFET (Fairchild BS170) to no avail. I guess there's no standard pinout for FETs because the BS170 actually does have the same pinout as the supposed original.
One other piece of information is that I measured the resistance between legs of each of the two components. Assuming I have the pinouts correct, the bad one measures: S-D: 204 Ohms, S-G and D-G are both about 10K. The good one measures: S-D: about 60K and S-G and D-G are open.
I was hoping that someone might be able to confirm that this part is in fact a JFET.
If anyone has any other advice on what might be a good replacement, it would be appreciated.
-David