The missing sockets are for diagnostic chips
The reason no blue back light and the wine os the backlight has failed and now there is very low resistance and the transformer is taking the load and is sqealing as ots trying to drive the backlight
The noise you spoke of is the small black box
Wjen you mentioned about the cpu making a noise a capacitor can make those wineing noise to and why I said check the bypass caps
But you explained the backlight inverter as the cpu
Yes you can get correct voltages but you need a scope to check the ripple for this you need to measure the dc lones as a ac signal and you can measure the ripple the smoothing caps after the rectifiers are the best place to check as you can use a dual trace for the ripple before the caps and test the ripple on the emax psu connectors
On the psu it gives you the voltages for the pins on the connectors
Check for 5v on the cpu
And see if youre getting the voltage on the screen and on pin 3 which should be .6 lower than the 5v max and it can have a range of 0-4.2-4.4 for the angle
If there is no voltage there you wont get any thing on the screen
I would bell out the connections to the screen as inthe past I have had broken leavers in the grip connector on keyboards
Racks dont suffer from this as they are hard soldered
Sent from Samsung Mobile
-------- Original message --------
From: "schtom83318@yahoo.com [emax]" <emax@yahoogroups.com>
Date: 21/12/2014 23:00 (GMT+00:00)
To: emax@yahoogroups.com
Subject: Re: [emax] Emax II service manual
I really want to apologize for any unrest in the group I might have caused. I really appreciate everyone's replies. I just want to get this Emax II up and running. Its a keyboard that has been on my bucket list. So could the power supply be giving the correct voltages but still have a problem with it?
I have the main board out and I don't see any caps by the processor. The only caps I see on the board are the x2 25v 10uf and the one 16v 47uf.
The CPU is in IC90 I have figured. I don' have a chip in IC4 or IC64-99 or RN6.
On the expandable memory board PC357 I have only chips in sockets IC54-57.
This is a model 2212. It really does not show any signs of someone messing around inside of it.
I just have that blank screen. I do see the blue backlight in it.
I did find the piece of the metal floppy cover in the floppy drive flopping around. I got that out. I'll check on seeing what happens when I unplug the floppy and power it up.
thanks,
Tom