Author Topic: s700 flickering LCD screen, hissing and crackling noise from speakers  (Read 1599 times)

0 Members and 1 Guest are viewing this topic.

Offline jimmi V

Hello all,  so I'm having flickering LCD screen and hissing and crackling noises coming from the speakers on my s700, so I did a search on this sight and found some are people had this same issue, the thread was since 2009. 
http://www.psrtutorial.com/forum/index.php?topic=9027.0
http://www.psrtutorial.com/forum/index.php/topic,10037.msg66393.html

Some suggested that it may be an invertor or LCD screen going bad?  So, I was wondering if anyone found or knows a solution that I can maybe do by myself?

UPDATE:  The screen flickering happens intermittently, comes and goes when it wants.  The sounds coming from the LR outputs seems normal, but I do hear faint crackling from the headphone jack.

Thanks
« Last Edit: December 01, 2016, 02:06:03 PM by jimmi V »
 

Re: s700 flickering LCD screen, hissing and crackling noise from speakers
« Reply #1 on: December 18, 2016, 12:40:00 AM »
Before you assume its the lcd, try and find someone or a retailer local to you to test a different power supply, a bad psu could give the same results due to a faulty rectifier or capacitors on the dc side, as they act as a buffer after the bridge recitfier ( didoes to convert the ac current )

Think of the capacitors as shock absobers on a car. If they fail it gets very bumpy. Same is in a DC current, instead of it being a continuous +16v it could flip between +16v and 0 either 50 or 60 times a second (pending on input source 110v 60hz or 250ac 50hz)

And as the PSU is cheaper than a new lcd, most keyboard shops (ones ive visited in the uk anyway) will let you try a known good psu on your board. 

Offline travlin-easy

Re: s700 flickering LCD screen, hissing and crackling noise from speakers
« Reply #2 on: December 26, 2016, 07:32:24 AM »
I suspect that one of the ribbon connectors are loose that connects to the LCD display. The fix would involve opening the keyboard, then unplugging and replugging the connectors to the screen and the opposite ends where they attach to the mother board.

Good luck,

Gary 8)
Love Those Yammies...
 

Offline Dave Aho

Re: s700 flickering LCD screen, hissing and crackling noise from speakers
« Reply #3 on: December 27, 2016, 03:21:21 PM »
I used to own 2 S700's . . . one did essentially what is  described here.  I took it apart and checked all of the connections as Gary suggested but never really fixed it.  I performed with it every day for about a year by reducing the overall volume a bit with the interior graphic equalizer and, of course, using an exterior amplifier which helped but it never became perfect, in my opinion. 

I bought an S900 and sold the S700 on EBay with no call back so it may still be working fine for all I know.  The other S700 was no trouble whatsoever but the S900 LCD went out and I had to replace it a few years ago. It is still working now  with the replacement although I only use it for a backup because I replaced the good S700 with an S910 that is my main machine now in my abbreviated retirement schedule.  But the sound quality is not anything to brag about even with the fix so I'm even more convinced of the correlation between the audio and video components. 

I determined the the problem with both the S700 and the S900 was heat related on the right side and although the LCD's were not the same, (mono/color) I still think the right channel power transistor was the root cause of the originalproblem in both models. I also used a couple of different power supplies on these machines and although I couldn't completely rule out "filtering" because I no longer have a oscilloscope, I think it still was proximity heat buildup between the audio power  and sensitive color video components in the stacked PC boards that took out the S900 LCD and not the S700 screen because I could change the symptoms by cooling the temperature in the right hand air vents of both machines. That's my story and I'm sticking to it!

Good luck,

Dave

Offline jimmi V

Re: s700 flickering LCD screen, hissing and crackling noise from speakers
« Reply #4 on: January 03, 2017, 10:16:22 AM »
Thank you all for you suggestions and sharing experiences.  I've since sold my s700 and got me an s950, luv it  :)