NEED HELP- MAZAK T-2 control stops with no warning

[pa2262]

Hello All,
Looking for some suggestions on what may be causing my QT15 T-2 to just stop for no apparent reason.
Until recently, I could restart the machine and all would be well for several hours or several days.
Then the other day, after I had to completely shut it off to reset an axis alarm I couldn't restart it.
If I hold the ON button in, some digital displays light up on the control panel and the monitor tries to come on but it's only black and white static and won't stay on.
Nothing else comes on.
I checked anything I could think of: fuses,breakers, power supplies, and out of place relays.
I swapped out circuits boards and even the PD14C-1 power supply.... nothing made any difference.

And I just had a local service tech spend a few hours going over it. Somehow he got it to come on.
He claimed he pulled a relay (SB) checked it, then put it back in and the machine came on.
It stayed on yesterday for about 5 hours with no problems.

It turned on this morning and was on maybe 3 hours. Then without any warning it just stopped.

From what I'm understanding, the 24V is not getting through to allow everything to come on.
There's a small 24V power supply on the back panel door- LSS37-24 which appears to be sending out 24V.
And there's 24V at the socket of relay SB as well.
BUT there's no 24V at the PD14C-1. I took my unit as well as a spare one and installed in a friend's MAZAK.Both worked fine, so there must be something else going on.

One thing I did notice is, that the OFF button on the front panel stays lit regardless of pushing (and holding) the ON button in. It's supposed go out when the machine powers up
Could there be something wrong with those buttons or associated circuitry behind them ?
Weather permitting, another service tech is supposed to show tomorrow . But if I can help things along with some advice from someone who's been down this road before, I'd really appreciate any input.
TIA

[servtech]

Check the keyboard power supply, Lambda I think, the size of a 20 pack of cigarettes. I've had problems in the past where this 5v drifts up and down causing issues.

[pa2262]

Thanks for the reply. This keyboard 5V power supply is located where ? On the backside of the control panel ?
There is a Lambda LSS-24 power supply on the rear cabinet door, but that is putting out 24V

[servtech]

Thanks for the reply. This keyboard 5V power supply is located where ? On the backside of the control panel ?
There is a Lambda LSS-24 power supply on the rear cabinet door, but that is putting out 24V

My recollection is it's mounted on the keyboard rack the rack might be under the keyboard or in the electrical panel. It outputs smoothed 5v to the keyboard diaphragm buttons and led's.