Yaesu ft2800m hum during tx

The problem is likely the TX/RX relay. If it is old (and I am sure it is) the contacts likely need to be cleaned, or the relay replaced. It is a common enough relay if you want to replace it. Also, pull each PCB card and clean the contacts with a pencil eraser. Pink erasers are OK but the white ones are better as they aren't as abrasive.

Hope this helps, VE3CMQ

I would like to help, but your question doesn't make any sense what-so-ever. Could you please explain it better?

I have had this occur when either my keyer paddle or cw key is pressed as if sending. In other words you are in transmitting mode.

I am not sure, but this usually indicates that the PLL has lost lock. These days, it could be as simple as a poorly soldered connection. I don't recommend that you try repairing this yourself as there are essentially no user serviceable parts in radios these days.

Radio repairs these days have come down to board swapping because the parts are so tiny that humans have a hard time replacing (and in some cases, seeing) the parts. Yaesu US has a very good reputation for quality repairs so I'd suggest you send it there. They will likely just swap a board out, but that will be less expensive than having someone spending 10 hours trying to find the problem and repairing it. I know, as I work in a radio shop, and if it isn't something real simple, all we can do is do a board swap.

Here is a link to a forum that has instructions for how to make the modification: http://www.worldwidedx.com/threads/expanded-tx-mod-for-ft-1900r.37171/

bad mic cable, bad capacitor somewhere

maybe some bad connection on RF output from final modul, resolder RF dioda n hot area arround them

You have probably a faulty VHF/UHF relay. It is RL5016 in LPF unit.
73 JOSE EB5AGV

has it been opened up to talk on

this address should help you out http://www.ham.dmz.ro/yaesu/vx-1r-ext-mic-diagrams.php
as for the service manual you will have to order that from yaesu or see if the local Ham radio sevice shop has an extra one they will sell.