Hello,

I have just disassembled the miner.
The voltage between coil and ground was:
10,5V on left side of coil when You look from fan side of the miner.
9,5 V on right side of coil.

The voltages are similar than other two hashboards (10,6V and 9,5V).

I have checked to crosscheck with other hashboard, to check if the problem is caused by controlboard or cables, but it looks there is problem on the hashboard.
The chips are cold during startup and on two next hashboards chips are hot at startup.

I think the chips have not power to startup...
What I saw TF LED not flash and on next two working boards it is flashing all the time.

Has somebody similar problem?
Do I have to solder 50k potentiometer?
Can somebody to sent the photo from first message of the topic because links not works right now?

Edited: I have soldered potentiometer but U2 was still on the board.
It was not helpful...

Next test - I have unsoldered U2 but there was no positive result.
Miner has to run with potentiometer 50k - it works.
I have still two "O" visible on one hashing board.
There is no other "O" or "X" visible on this board.
Total speed is 3.2 Thash/s.

Any person can help me in this case to speedup the miner??

Can You describe what choke coil do You mean?
Can You provide some photo of the choke coil? 

Is there some possibility to check it without disassembling the miner?

Hello,

I have only two "O" on one hashing board.
There is no other "O" or "X" visible on this board.
Do You know 50k potentiometer will work in this case?
https://imageshack.com/a/img923/7604/R6IfkG.png

I have tried to reduce the frequency but the problem was still occurred.