I know the MRF-250 is not exactly made to hardwire to an IR in jack. Nor is it the greatest product. But I have a situation where I'd like to wire one directly into a Yamaha RX-V2700 reciever.

Can I just make a patch cable for 2.5 mm to 3.5 mm?

Is the output level too high? (Somewhere I remember reading about throwing a 330 ohm resistor in).

Usually I'll just use a MRF-300 or MRF-350 but I have an MRF-250 I'd really like to use here.

Yes the output level is too high. You'll need some sorta resistor, dont know the value off the top of my head.

The main issue is going to be reliability, not the RF output. Many agree that the MRF-250 should be discontinued. It simply isnt worth saving 30 bucks. Must admit, I used one on a job recently though just to get rid of the damn thing. All it has to do is turn a TV on and off, and i made goofy macro's to make it more reliable.
IE:
OFF- tv-off, delay .5, tv-off, delay .5, tv-off.

works like a charm now :)

I'm aware of the MRF-250's problems. It's an extra I have and don't feel like getting another one. (Don't worry, I'm a DIY'er, its for myself).

The interference isn't too much of a problem, I've gotten it to work well with the ferrite core thing plus removing the antenna.

I believe someone once mentioned 330 ohm...I'll try that first. If not I'll adjust accordingly. Or maybe I'll wire a Pot in for adjustable output...

The MRF-250 was more reliable then the MRF-300 for me... after adding RFI filters it may finally be perfect.

I use 4-5 MRF-250s a week. I am sure there are other dealers that use way more than me. Would you really buy an MRF-300 for a MX-350? They realy do have a lot of valid uses. Just not with an MX-3000 in a 50k dedicated theater where the gear is 100' away and the home is in the shadow of NASA'S program to communicate with aliens.

'
Uh oh, I saw this note but didn't realize that the output was too high on the 250. I have one, and made a little cable to plug directly to my pre amp and it seems to work fine. What bad things can happen? Or, how and where do I put in the little resistor?