Follow the colors, and you know where the PCB trace goes. Also the U1000/U1001 pdf datasheet added. Good luck.
Thank you for the service port information. Do you think if I use TX,RX and GND signals (with an appropriate voltage bridge) I will get a correct output, in case the CP2102 is faulty? I have two DM800SE that have strange output in Putty. I changed Y800 but it did not help.Thanks
I've tried that with a rs232 module from a vu duo box to make it serial instead of usb but it not works. I think because it can't work when the usb chip is still connected to the rx/tx circuit. Without the usb chip I have still not tried. In any case it is not a normal rx / tx connection, it needs a chip.
Thanks for the reply. I think Rx/TX is a kind of UART connection. And U90 is a simple USB TO UART BRIDGE. I simply use Arduino Uno ( without the Atmel chip) as a USB bridge. I connect Arduino to my laptop via Usb, and RX,TX, GND connect to RX,TX,GND on a mainboard where I need UART output to be shown in putty. And it generally works. But my problem is strange character with this mainboard. You mentioned VU receiver, did you have a time or will you have soon to check if you are able to change a register's value of the CPU of VU and if it remains after rebooting? When I tried with BCM7405, the changed value returned to the default after restart. Thanks
Yeah okay, but what if the USB chip has a problem on the Rx / Tx CPU side, then a second chip on the circuit will show the same. At least, it seems to me logic. Maybe you can find some issue if you measure the rx/tx with ohm, and compare the values with a good one. And no, I have very little free time to pick out special cases. But I have discovered at the wrong 800se cpu, if I enable the debug, and Flash sector recovery in the bios, it seems to start further. Unfortunately I had not the time to examine it further because of the many repairs I have.
Yes, as I can see I must still learn from expert like you. But just to check th eproblem again I removed U90 and tried again with UART but the same. But I checked voltage ( and frequency ) on Y800 and it was only about 0.6V, while another DM800SE had about 1.3V on Y800. So I wanted to know where the voltage is coming from. I would say it is from CPU ( Correct?or wrong?)I found out the voltage from CPU is coming to R806 and R803, so I desoldered them and measured voltage.Again on the faulty DM800 was about 0.3V. Do you think CPU is faulty? Regarding faulty CPU you say: But I have discovered at the wrong 800se cpu, if I enable the debug, and Flash sector recovery in the bios, it seems to start further. I tried to set various options with BIOS( pressing S character to start BIOS) but after restart there was again the default value. Is it normal? Thanks
See this drawing for the tracks to the Y800. But, I advice to measure the ohm value between these two tracks, best is to do this without the crystal. Normally this doesn't matter because the crystal gives no ohm value, but by a defect it can. Also, best is to measure it between the R803 and the R806 cpu side, this to exclude the other parts. In any case, if you have a good measurement between these two tracks, you may assume that the tracks to the cpu dots are fine. That is, if the C801 is not shorted. If not, bad solder contact with one of the dots, or defect cpu.
Thanks for the reply. SO I measured : Good DM800SE: Between crystal 1.7k Ohm, between R806 and R803 1.6k Ohm Faulty DM800SE: Between crystal 1.9k Ohm, between R806 and R803 1.7k Ohm Do you think are values OK?
The ohm difference is not something to worry about. For example, Good DM800SE Ferrari RevD4: Between crystal 16.71k Ohm, between R806 and R803 16.51k Ohm. Good DM800SE Estar Rev9: Between crystal 14.94k Ohm, between R806 and R803 14.79k Ohm. Although you measure there a wrong vdc value, it seems not to be caused by this circuit. I think it only gives a indication that there is something wrong. I'm guessing a cpu issue, but it's not to say for sure.
Sorry I have overlooked it, No if you have saved the settings, it must stay. Only the Flash sector recovery setting disables after a reboot. Therefore you must enable this, as choose use this settings once. And, all these settings are stored into the U8 two-wire serial eeprom. More info about this ic see the datasheet. U8-FT24C04A Datasheet.pdf
Thanks for the info. I work like this: Start Putty program start DM800SE wait for "S" to enter BIOS Change values in BIOS I need I use one of the SAVE option (From the last menu in BIOS, ) ENTER Do you use the same procedure to save the changed values of BIOS?
Hello, Tell me, please, the value of resistors R808 and R809 ??? Ohms. Hi, Help my. Tell me, please, the value of resistors R808 and R809 ??? Ohms. DM 800 SE Thanks
Ohm value measured between the ground and the resistor Both are bridges, so both are 0 ohm resistors. R808 both sides 0.486k R809 is a ground bridge.