Problems with my Tri-Vista 300--Need some help

My new Tri-Vista integrated has worked beautifully for a month, but yesterday, for the first time, I discovered that no sound is coming through the right terminals into the speaker. I tried shifting speakers and cables around and found that it has to originate with the amp. The amp has two sets of binding posts, but in changing the speaker cables to either of them, I've still gotten no sound out of the right side. Could this be a problem with an internal fuse, and if so, and since I have no MF dealers here in Korea (I bought off the net), what might be my options in terms of getting the amp repaired? Any suggestions?
But cant MF supply you with the spare tubes ? I thought they had one extra set per amp manufactured or was it the Nu Vistas ? I cant remember....Perhaps you can try Wim Bouwman at Mr Valve in South Africa,my local tube supplier,chances are slim but I think worth a shot ...mail is
Thanks Chris. Looks like I may have finally hit paydirt over here. Triode Electronics in Chicago finally came through after two weeks it seems. Going to have these tubes on Friday. I was getting worried after substantial waiting that they wouldn't be able to get them. Ordered ten for six dollars each. Cheapest I've seen:

MF will supply the tubes but they want to see the originals first. At least that's what the dealer said in Hong Kong. Pretty inconvenient. I'll post again after I get them by fedex next week and take them to the shop.

They probably want to see the originals if they are going to replace for free. I was told when I bought my TriVista that I could order a second set any time, that they set aside an extra pair for each unit.
I want to thank everyone once again for your replies on this thread. I managed to get my amp back today with new tubes. Indeed, the original trivistors were faulty and are now replaced. Probably the first instance of bad tubes on this gear.

Secondly, there is indeed a big problem with the source selector on this machine now. Wasn't when I initially took it into the shop, but I don't doubt the repairman's integrity. I brought it back home and when i turn it on, it travels the circuit around the sources, but rather than settling on the most recent source, as normal, it starts to click repeatedly against either the top or bottom of the source array. I finally grabbed the selector and tried to forceably put it on the proper source. Finally, it stopped this strange behavior and I could listen to music again. I'm going to have to get a new selector chip and replace it in the amp. Has anyone else had a similar problem with this amp? Thanks.
My Denon does the source selector thing! The most annoying thing! I had been extremely busy, and then very tired, and then when I felt up to dealing with it it stopped as mysteriously as it started. Funny thing- I thought I would be relieved to read that someone else had this problem, and I am in part. But it is frustrating not to understand how my amplifier works- as it must be for you, especially when everyone must seem miles out of reach and real information a real commodity. It puts my situation in a new light, and I thank you for that. I wish I could tell you I had your amplifier( for all sorts of reasons) and that I knew why the source selector behaves this way and what to do about it. I would love to tell how to deal with that. I would love to be of some help! All I can really do though is admire the intelligence and patience you have displayed in sorting out your problems. The input selector chip seems a reasonable quess. Hopefully others here have had this problem and will be able to help you figure it out, and that MF will offer some insight too. In the meantime, even as my lowly, but much beloved Denon is behaving itself I am resolved I will learn something about these amplifier related quirks, and if I learn anything soon enough and reliably enough I will try to pass on what I have learned. I am sorry you have to put up with all this ( my long post included) and I wish you luck.