[Galaxy Tab Q&A, Help & Troubleshooting] DrGolem1:
Thank you for this suggestion. Unfortunately it doesn't help. I downloaded Sbl image and run it, but it stacked somewhere in UART2 transmition.

Will try to connect to UART lines to see what's output there.

Here is my logs of OpenOcd session

connected and halted board

Open On-Chip Debugger
> halt
target state: halted
target halted in ARM state due to debug-request, current mode: Supervisor
cpsr: 0x600001d3 pc: 0x40205450
MMU: disabled, D-Cache: disabled, I-Cache: enabled

> arm disassemble 0x40205430 15
0x40205430	0xeb004b0f	BL 0x40218074	; ?? call some verification function
0x40205434	0xe1a03000	MOV r3, r0
0x40205438	0xe3530000	CMP r3, #0x0
0x4020543c	0x0a000004	BEQ 0x40205454	; result OK, jump _VerifyOK
0x40205440	0xe59f002c	LDR r0, [r15, #0x2c]
0x40205444	0xebfffdff	BL 0x40204c48	; printf "PBL: Error.. sbl verification failed.."
0x40205448	0xe59f0028	LDR r0, [r15, #0x28]
0x4020544c	0xebfffdfd	BL 0x40204c48	; printf "PBL: booting stop!"
0x40205450	0xeafffffe	B 0x40205450	; halt
; _VerifyOK
0x40205454	0xe59f3014	LDR r3, [r15, #0x14]	; r3 = 0x4053924c
0x40205458	0xe5933000	LDR r3, [r3]	; r3 = 0x40244000
0x4020545c	0xe12fff33	BLX r3	; call Sbl at RAM 0x40244000
0x40205460	0xe24bd004	SUB r13, r11, #0x4
0x40205464	0xe8bd8800	LDM r13!, {r11, r15}
0x40205468	0x402186e0	EORMI r8, r1, r0, ROR #0xd

lets insert NOP (0xe1a00000) at 0x40205450 to continue execution

> mww 0x40205450 0xe1a00000
> arm disassemble 0x40205450 3
0x40205450	0xe1a00000	NOP
0x40205454	0xe59f3014	LDR r3, [r15, #0x14]
0x40205458	0xe5933000	LDR r3, [r3]

one more thing, let's put a breakpoint at start of Sbl

> bp 0x40244000 4 hw
breakpoint set at 0x40244000
> resume

after a while board halted at breakpoint

target state: halted
target halted in ARM state due to breakpoint, current mode: Supervisor
cpsr: 0x600001d3 pc: 0x40244000
MMU: disabled, D-Cache: disabled, I-Cache: enabled

remove breakpoint

> rbp 0x40244000

let's check where we are

> arm disassemble 0x40244000 15
0x40244000	0xea000007	B 0x40244024
0x40244004	0xeafffffe	B 0x40244004
0x40244008	0xeafffffe	B 0x40244008
0x4024400c	0xeafffffe	B 0x4024400c
0x40244010	0xeafffffe	B 0x40244010
0x40244014	0xeafffffe	B 0x40244014
0x40244018	0xeafffffe	B 0x40244018
0x4024401c	0xeafffffe	B 0x4024401c
0x40244020	0x40244000	EORMI r4, r4, r0
0x40244024	0xe10f0000	MRS r0, CPSR
0x40244028	0xe3c000ff	BIC r0, r0, #0xff
0x4024402c	0xe38000d3	ORR r0, r0, #0xd3
0x40244030	0xe129f000	MSR CPSR_cf, r0
0x40244034	0xe59fd17c	LDR r13, [r15, #0x17c]
0x40244038	0xe3a00000	MOV r0, #0x0

load Sbl image and resume

> load_image Sbl.bin 0x40244000 bin

> resume 0x40244000

Tab still dead, no USB, no screen. If I halt it, it stacked at this function.

Code waits for transmit empty (UTRSTAT2), but UTRSTAT2 value always #0

40253394:	e52db004	push	{fp}	; (str fp, [sp, #-4]!)
40253398:	e28db000	add	fp, sp, #0
4025339c:	e24dd00c	sub	sp, sp, #12
402533a0:	e50b0008	str	r0, [fp, #-8]
402533a4:	e59f302c	ldr	r3, [pc, #44]	; 0x402533d8 r3 = 0xe2900810 (UTRSTAT2)
402533a8:	e5933000	ldr	r3, [r3]
402533ac:	e2033002	and	r3, r3, #2
402533b0:	e3530000	cmp	r3, #0
402533b4:	0afffffa	beq	0x402533a4
402533b8:	e59f201c	ldr	r2, [pc, #28]	; 0x402533dc r2 = 0xe2900820 (UTXH2)
402533bc:	e51b3008	ldr	r3, [fp, #-8]
402533c0:	e5823000	str	r3, [r2]
402533c4:	e3a03000	mov	r3, #0
402533c8:	e1a00003	mov	r0, r3
402533cc:	e28bd000	add	sp, fp, #0
402533d0:	e8bd0800	pop	{fp}
402533d4:	e12fff1e	bx	lr