130XE mmu

[TXG/MNX]

 

Hi

 

I am troubleshooting an 130XE

 

I have a question the MPD pin14 of mmu to which chip pin should it be connected?

It also goes to R15 but I cannot find that resistor on the board.

 

Solved.

 

So far pin 15 has no connection so that needs to be fixed.

 

Only pin 15 needs a new connection. Pin 14 need to be connected to the near via.

 

Fingers crossed [emoji41]

 

 

 

 

 

 

[Rybags]

Do you have the 130XE schematics?

 

/MPD is Math Pack Disable and is an input from the ECI, so doesn't go to any other chip on the computer.

/BE is Basic Enable which comes from PB1 on the PIA.

/MAP is from PB7 on the PIA - Self Test Rom select.

REN is from PB0 on the PIA - OS Rom enable, note it's active high unlike the other Rom selects.

 

Link for handy system board and chip info https://www.atarimax.com/jindroush.atari.org/atech.html

[TGB1718]

Have a look at these circuit diagrams

[TXG/MNX]

Have a look at these circuit diagrams

Thanx i had that only but it was a puzzel to find exactly where some traces would go. But I found two issues I will fix and test.

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[Mathy]

Hello TGB1718

 

9 hours ago, TGB1718 said:

Have a look at these circuit diagrams

 

Why not use the original ones here?

 

Sincerely

 

Mathy

Edited June 17, 2020 by Mathy

[TGB1718]

Thanks for the link, but I think the "Left Side" is missing part of the circuit at the extreme left edge.

 

But also more good infor on other Atari gems

[Mathy]

Hello TGB1718

 

I just checked.  You are correct.  But this is how they apparently came from Atari in the Netherlands.

 

Sincerely

 

Mathy

[Marius]

With all the respect for mr. Sobola's work, I can not remember I ever used a schematic from his hand that was not faulty. So please be careful with just using that schematic without checking everything twice or more.