I am posting the following as a service to all 817 owners. Even if you do not experience these 70cm transmit problems, I would not be surprised to find out that this fix also improves receive by making the radio quite a bit more quiet---here is my story
Recently I found that my 817 occasionally did not put out any power on 440 transmit when using a duck on the front BNC.
Further examination showed that when set to low power and the antenna was flexed just so the power meter would peak but actual output power dissappeared.
Some experimentation showed that grounding the big covered can on the main board solved the problem. A bit more investigating showed the bottom of the main board is not well grounded.
A little search work produced the official Yaesu fix document (the actual document used at Yaesu) along with part numnbers needed to implement the fix (avaliable from Yaesu, or you can send the rig to them and wait for them to repair it). Yaesu will fix the rig for free if it is under warantee. If not you will have to order the fix part (the part# is in the attached tiff file), dont worry it only costs .22 USD (22 US cents).
This is not a lot specific problem (according to Yaesu), and rigs as recent as a year 2001 lot 44 rig has the problem (A rig produced around the end of 2001).
PLEASE NOTE, CONTRARY TO THE OFFICIAL YAESU FIX SHEET, THIS PROBLEM WILL AFFECT THE 817 EVEN IF IT IS USING THE INTERNAL BATTERY PACK!!!
The official Yaesu fix is under the filename, 817ground.tif.