Mx135 subwoofer not working???

Hello. Ive tried everything to get the sub working in the pure stereo mode. I am using analog inputs. Speaker size set to small, subwoofer: yes. The sub works fine in ANY other dsp mode...cinema, music123 etc. so i know the sub out is working. Also updated to latest firmware. Any thoughts? Thx!
I owned an MX135 but it's been a few years, so forgive my "guess
from faded memory". But I seem to recall that you must set the cross
over in the 2 channel settings menu, but I really seem to recall that the
"pure" excludes the subwoofer. Also if you haven't experienced
this, I definitely do remember having to do a capacitance reset, by
unplugging the unit and press every switch and turn the knobs while it is
unplugged. That allows the processors to return to their default settings,
and sometimes that helps get a setting change to be accepted.
Good luck, but look at your manual, I really do think that the subwoofer is
not used in pure mode. But could be wrong, dang that could hurt! :)
If the mx-135 is designed similarly to my mx-120, then Pure Stereo mode should output a sub signal, and 2-channel mode, no sub signal. Did you try doing a hard reset?

if you want the best sub in the market, sell your current sub and buy a REL. These are the most musical sub out there.
Everything else is a waste of money. Keep me posted & Happy Listening!
I'm convinced Jafant is an auto spambot that searches for the word subwoofer, and adds irrelevant non sequiturs to REL products.

Be sure to keep it posted.
Still having no luck. But have noticed that sub out does work for 10-15 minutes, the gradually fades to no output. Again, this is only in pure mode. I have ruled out the subwoofer itself. Sub out works great in any DSP mode, just not analog stereo. Perhaps it is a heat or capacitance problem?

That's a bummer Tom. It sounds like you might need to enlist the help of a service tech for this fix. Audio Classics in Vestal, NY could help you out. Give Ryan a call. These guys are extremely knowledgable and do great work. Best of luck!
Tom, it does sound heat related. I would call McIntosh, they are very good at helping you diagnose and also in the past they done repairs for me, and although out of warranty, it was still free. I just paid the shipping to them and they sent it back at no charge. Not saying it is policy, but worth a try.
They never indicated it would be free before I sent it, it just worked out that way. They are a great company to work with.