Sony with MBX-224 mainboard problem

[giove]

hi, i have a problem with the indicated motherboard. the power on led lights up but does nothing. the checks made are missing the + 5vrun and + 3vrun power supplies. precisely the anomaly should be in the part of the circuit indicated. I have inserted the power supplies in green. thanks

[Techtiger]

Re: Sony with MBX-224 mainboard problem

first check 3/5VALW is ok , then PQ29A Gate voltage? PQ47 & PQ27 Gate Voltage must me Aprox 9.89V to switch on the Gate

[giove]

Re: Sony with MBX-224 mainboard problem

hanks for the reply, the 3valw and 5valw voltages are correct 3v and 5v. on the gates of the PQ29A as shown in the picture there are 3.3v while on the gate of PQ27 e PQ47 there are 0.4v.

[Techtiger]

Re: Sony with MBX-224 mainboard problem

hanks for the reply, the 3valw and 5valw voltages are correct 3v and 5v. on the gates of the PQ29A as shown in the picture there are 3.3v while on the gate of PQ27 e PQ47 there are 0.4v.

test the voltage on PR130 PA131 both side's PQ47 Drain side ?

[giove]

Re: Sony with MBX-224 mainboard problem

I have indicated them are 0.4 v both

[Techtiger]

Re: Sony with MBX-224 mainboard problem

PQ31 Source need +12V if it's not there trace it back when this Fet switch on with the help of SUS ON PQ31 Drain gets +12_1 this Voltage pull up from there to PQ131 in put side
PR130 need +5VALW if it' not their tarce it back or put a jumper form +5VALW , PQ47 Drain must have +5VALW if it's not there trace it back , Do a continuity test PL16 to PR130 PQ47

[giove]

Re: Sony with MBX-224 mainboard problem

as I indicated the voltages 12V_1 5valw 3valw are present and are respectively 13v, 5v and 3v

[Techtiger]

Re: Sony with MBX-224 mainboard problem

as I indicated the voltages 12V_1 5valw 3valw are present and are respectively 13v, 5v and 3v

change (PQ29) PQ29A Drain should be Negative voltage you have 0.4 when than Negative voltage reach Gate of PQ29B that fet get off letting +12V to gate of PQ47

[giove]

Re: Sony with MBX-224 mainboard problem

so do you confirm that I need to replace pq29AeB 2n7002dw?

[giove]

Re: Sony with MBX-224 mainboard problem

I replaced the component but unfortunately does not go. compared to before it stayed on now after 1 second it goes off. the other does not allow me to take measurements ...what can i do?

[giove]

Re: Sony with MBX-224 mainboard problem

but should the "xVALW" voltages always be present? I noticed that when I plug in the power cord they are present and after about 20 seconds they disappear and when I press the power button they reappear and then disappear after 20 seconds

[mcplslg123]

Re: Sony with MBX-224 mainboard problem

Lots of sony mb has this feature like mbx223/224/269. The +3V/+5V ALW will appear on coil for 10-20 seconds and will go away. thats the feature of this mb. So dont worry about that. your problem lies elsewhere. I'm 100% sure of what i'm writing as yesterday only i repaired a very complicated case of MBX-223 which came after several attempts to repair by earlier technicians.

[giove]

Re: Sony with MBX-224 mainboard problem

thanks. What can I check?