Problem with riff box?

[Mirco]

I can't connect the phone. although previously connected. I started to check everything and noticed that the VCCQ line is only 1.35V and when you try to change the program, it does not change. Constantly remains 1.35V. Could there be a problem?

[Legija]

Try to reconnect box and restart PC, if problem remains it could be faulty regulator.

[Mirco]

tried, restarting the computer does not help. On the VCCQ line, it's still 1.35. What kind of regulator is meant?

[Mirco]

here are the voltage measurements from the box

[mtk6572s4clone]

Try replacing the "V2" regulator.

[Mirco]

ok I'll try

[Legija]

First, remove all that mess you installed on box board, because nothing there is according to instructions.

[Mirco]

There, in fact, everything is done as in the instructions, installed resistors for tightening CMD and CLK. It worked like this for more than a year. Regulator V2 replaced, no result. What could be the problem? Why does only 1.35V come to the regulator? As far as I understand, 3.3 should come there and the required voltage should be issued through the control. Am I misunderstanding something? By the way, I took away all the so-called "mess" - there is no result.

[Legija]

V2 is power regulator and it's input voltage level is 5V (or whatever level is at USB port). It's output voltage level is variable (from 1.6 to 3,.3) and it's controlled by digital resistor U4.

On "mess" of course that you did there things wrongly, you connected 4.2v from V3 to I/O pins over resistors, which is of course wrong.

[Mirco]

take a look at the photo I posted to the V3, nothing is connected to me. In the photo there just hangs a disconnected cable from the track where the VCCQ is fed, according to the instructions installed in the boxing program itself. Probably that's why it seemed to you that I connected something to the V3. If I understood correctly then the problem may be in the resistor U4, what it should be there, can I get the marking? I had a thought that there might be a problem with it just right, but I don't know its labeling to try to replace.

[Mirco]

can you provide the marking of resistor U4?

[Mirco]

noticed that at the time of connection to the PC all the voltages on U2 are normal. And as soon as the PC is assigned, immediately the voltage VCCQ drops to 1.35v. And at the same time the input stabilizer U1 and logic xc95288xl start to heat up quite significantly. Probably a problem with logic, then along the way I can not do anything and unfortunately I will not repair the box. Apparently, I can't wait for your comments.