MP-1 no display or LED's

[andtimebegins]

It came on like in the video while I was testing, but I'm not sure if I was physically touching anything when it came on.

I tried pressing down on some of the IC's on the right... no luck

So I noticed just probing all the pins on U40 and U41 that only a handful of the pins actually showed a reading. So do you think I should go ahead and replace those?

Also, that reading on pin 20  of the eprom seems to really fluctuate a lot.

[MarshallJMP]

Yes that's correct, U40 p 4,5,6, the rest is used in the reset circuit and stays at the same level after startup, same for U41, only p 1,2,3,4 will change. So you could try to replace them since they are cheap parts. On the other hand it could be something else. Could be a bad chip that is hooked to the address or data bus. If one of those inputs is pulling the bus down you can get some very weird behaviour. So it can be an adventure sometimes. 
But I'll try my best to help you out the best I can, and I hope we can solve it.

[andtimebegins]

Would you like me to post pictures of all the data and address bus pin readings for the Eprom or the ram, or both?

[MarshallJMP]

No that would be too much work I guess.Just check to see if you have have signals.

[MarshallJMP]

So any updates?

[andtimebegins]

So any updates?

I've been kinda busy.. had to put my mp1 in my storage shed for a bit.

I'll definitely be back at it soon!

Thanks MarshallJMP!

[MarshallJMP]

Ok just let us know.

[andtimebegins]

Well, sorry for the long delay in replies on this one... I ended up fixing the Mp-1!

Here is what happened:

A good deal on a working Mp-1 came up near me, so I bought it. I figured I'd try swapping out chips to see if that would make the broken one work... nothing. Then I figured I'd try swapping the transformers out just to be sure. I installed the working transformer into the broken Mp-1, and it started working!! :headbanger:

I figured I'd try the removed "broken" transformer into the other Mp-1 I had just gutted.. and now that one worked!! I noticed a bad crimp when removing the little wire connector on the white wire coming from the transformer. The wires weren't tightly connected to each other. I'm pretty sure that was the issue all along! So now I have two working MP-1's!!! YAY! :banana: :headbanger:

[rnolan]

 

[MarshallJMP]

Well that was strange, but hey it's fixed !!! Great job you did.

[Iperfungus]

We've a specific way, here in Italy, to indicate such blatant luck...  :lol: