JTAG connection to control board
My problem is that I don't know where to connect JTAG connector. 


There may not be a JTAG connector on the board. Some designers deliberate don't include them (or even the relevant tracks) on production PCB layouts.


  There is no 14 pin header on the control board


That is just one of several "standard" JTAG pinouts - 10 and 20-pin headers are other common types. (I don't think that the TMS320F2808 uses SWD - but if it did, that uses only 2 pins + Gnd, making it even easier to "hide" them amongst other traces on a PCB.) Therefore don't assume you are looking for a 14-pin header, or even any header at all.


  Can somebody give me an advice how could the connection point for JTAG look like?


No, because there is no guarantee what those connections will look like on your PCB and, as I said, a JTAG header or connection points might not even be provided on the PCB! If the designer didn't want to make later JTAG connection easy, then they may have deliberately obscured those connections (even if they exist), so we couldn't tell you what they will look like.

You could start by looking for any silkscreen markings on the PCB, with the names of the JTAG signals.

If you supplied photos of the top &amp; bottom of the PCB, then readers here might spot something - but might not.


  I haven't any schematic to this board.


Therefore you will need to reverse-engineer some of it.

If the TMS320F2808 on the board is in a QFP package, then it is easy to look at the JTAG pins on the package and see if there are any traces leading from those pins, to test pads or other connection points. If not, then it is possible to carefully solder wires onto the QFP pins themselves.

However if the TMS320F2808 on that board is in a BGA package, then finding any unmarked JTAG traces (if they exist), or finding connection points for the JTAG signals, could be much more difficult and require X-ray or BGA removal techniques, for example.

If you want help from readers here, the next step is for you to supply those photos that I mentioned (clear, close-up, in focus, and taken from directly overhead the PCB), both sides. If that is not possible due to commercial confidentiality, then you may need to pay for someone with reverse-engineering skills to help "in person".

Finally: I don't know the TMS320F2808, but on some ICs it is possible to disable the JTAG pins after programming, as an anti-reverse engineering technique. If that applies to that IC, you might find that the JTAG interface is not actually usable.