You might inquire on eHam or look in QST. Unfortunately the TS-830S is an older unit and Kenwood probably doesn't carry the unique boards and parts any longer. I know that support for the TS-930S and TS-940S I owned at one time were discontinued. It's a pain. Good luck.
You might want to check with Kenwood to see if they can still service your 830. They have a center in CITY OF INDUSTRY, CA (phone is (626) 333-2443), which may be pretty convenient to you.
There are also several independent repair centers that handle Kenwood Amateur Radios (these are from a Google search and I can't vouch for their quality):