I understand what you desire to do .... it is easier as an electronics experimenter to live in Hong Kong or Tokyo to have access to individual parts. My Chinese orders take 3 weeks to arrive, and US suppliers/retailers/distributors today are just larger Eastern Asian import operations.
I've found a TS-680s to play with, but noticed there was no PC tuning interface, so I'm designing my own using somewhat newer technology than Kenwood's IF-10 parts. I've actually got it a USB FIFO wired up to the TS-680's Z80 CPU and it is working on my breadboard.
THAT is why Piexx exists .... reduce the upfront costs for individual radio amateur to acquire individual parts, some requiring qty. 100 orders from off-shore (Eastern Asia) manufacturers.
TS-140 / TS-680 serial interface (IF-10c).http://www.piexx.com/index.php?main_page=product_info&products_id=21
Does anyone know a part number for CN8 and CN9 on the TS-140 and TS-680 and their corresponding connectors? I found the Kenwood part number in the service manual, but couldn't find a supplier for it.
OEM parts supplier to Kenwood, was Japanese based. Many of these Japanese OEM parts suppliers have limited distribution in North America, leaving Kenwood Parts (East or West) as your primary portal for Kenwood parts.
Same issue with Icom and Yaesu. Some of the original OEM electronics part manufacturers for the Japanese Big 3 (Kenwood, Icom, Yaesu) -- as well as the Japanese automotive industry (Honda, Toyota, Nissan), were located in Northern Japan prefectures, that were wiped out in March 2011 Earthquake and resulting Tsunami /Fukushima nuclear plant radioactive zone.
19,000 Japanese were killed or missing (washed out to sea); over 300,000 were displaced from their homes.
The Denver Post photo essay shows the devastation ... Villages, people and factories - Gone.http://photos.denverpost.com/2013/03/11/photos-japan-marks-2-year-anniversary-of-tsunami-earthquake/