MP-1 no display or LED's

[Iperfungus]

Well, bad news guys.... it didn't work.

I ordered 2 of the same chip. Both with the same results as before.

NNNOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  :dunno: :dunno: :dunno:

[MarshallJMP]

Could be that it's either the device before the nand gate or the RAM (although I doubt that).

[andtimebegins]

First pic is pin 8 of u44 with new chip
Second pic pin 13 of u44 with new chip

Pin 8 seems to be behaving a bit different than with the original chip in.

[MarshallJMP]

What about pin 9?

Also measure on pin 3 of U41, since you have 2 channels measure with ch 1 on pin 3, with ch2 on pin 4. Since U41 is an inverter the signals should be exact the same but inverted.

[andtimebegins]

I'm sorry. I said pin 8. But meant pin 9.

I'll check those others now.

[andtimebegins]

Not much room to hook my probe on those pins, but here were my readings on pin 3 and 4 of u41. Bottom is pin 3, top is 4.

[MarshallJMP]

Mmm very hard to see, does it still changes when you start up vs a second later?

[andtimebegins]

That fade in and out was on pin 9 of u44

It does not do that anymore.

[MarshallJMP]

But it still does the same thing, it starts up with the leds on the left then on the right and stops?

Long shot, but try to pull the RAM out (U31, either 5864 or 6264) and put it back in, this will clear the RAM. Do this with the unit off!!

[andtimebegins]

Yes, the LED's behave the same. I notice the LED's only do that when the unit has been powered down for a while. If you start it up quickly after its been powered down, the led's don't really come on. Same with the screen.

I pulled out the ram. No change.

[MarshallJMP]

Ok, check all the data and address lines on the eprom and RAM chip. Just look for activity on each pin.

[andtimebegins]

Seems to be activity on each pin of the data and address channels. Im not sure whether its proper readings but my scope reacted to each pin.

Id say if anything ,pin 2 (A12)of both chips seem to have a very faint /weak reading..

[andtimebegins]

So interesting... in the middle of testing, the screen powered on for about a minute. It said no  and I pressed the edit button and it had a 9. I could see that it was trying to come on all the way. Then it faded out again. Thats the longest I've seen it come on. 

MarshallJMP. I was able to catch a video of this. I'll send it over.

Also. I notice the amount of time the screen stays on in the initial power up is longer than it was with the old u44.

[andtimebegins]

 I'm noticing pin 20 of the eprom seems to fluctuate between looking like this(see first attachment) and how it did earlier in this thread(see second attachment). So pin 20 of the eprom is not consistent.

[MarshallJMP]

Pin 20 is also a chip select line (CS). Just like the RAM. Now these 2 have U41 in common. Just a suggestion, try to replace U41 and U40 if you can, see if that helps.

Edit;I just saw the video you send me, did this happen al of a sudden or when you were measuring? Maybe a bad contact somewhere? What happends if you push on the pcb near the ram/eprom or more to the right on one of those digital 74 IC's? Maybe a bad through hole somewhere?