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by 1024MAK
11 May 2019 21:51
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 226
Views: 17698

Re: Resurrecting an MTX500.

You can also use HM4816 or equivalent DRAM chips...

Mark
by 1024MAK
11 May 2019 10:48
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 226
Views: 17698

Re: Resurrecting an MTX500.

You can also feed the Y output from J12 pin 2 to a composite monitor or SCART TV. The signal needs to go through a resistor to form a voltage divider as the 9929 outputs a nominal 3v peak voltage, and composite 1v (on SCART at least) 470R is the resistor value I found "on the net". That to me seems...
by 1024MAK
11 May 2019 02:13
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 226
Views: 17698

Re: Resurrecting an MTX500.

With the PAL video board, if using the baseband / composite video output, you can by-pass the LM1889 by removing link 'a' and fitting link 'b'. You should then get a monochrome video output. Note that C52 is deleted and replaced with C63, 100uF 16V or 25V (I recommend 25V). Note that C51 is deleted ...
by 1024MAK
11 May 2019 01:43
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 226
Views: 17698

Re: Resurrecting an MTX500.

8k ROM decode for Z80 CPU using a single 74xx138
8k ROM decode for Z80 CPU using a single 74xx138
8k ROM decode for Z80 CPU using a single 74xx138
8k ROM decode for Z80 CPU using a single 74xx138.png (37.21 KiB) Viewed 756 times
Mark
by 1024MAK
11 May 2019 00:52
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 226
Views: 17698

Re: Resurrecting an MTX500.

8k ROM decode for Z80 CPU using a single 74xx32 8k ROM decode for Z80 CPU using a single 74xx32.png While you were taking measurements, I drew this in case it helps. It only decodes the one 8k ROM. So use it in addition to the GAL/PAL and replace the ROM CS with the output of this circuit (use a tes...
by 1024MAK
10 May 2019 23:48
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 226
Views: 17698

Re: Resurrecting an MTX500.

What is the state of the other inputs to the GAL/PAL (6A)?

Mark
by 1024MAK
10 May 2019 22:49
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 226
Views: 17698

Re: Resurrecting an MTX500.

You mean this book...
Cover of Z80 Applications by James W. Coffron.
Cover of Z80 Applications by James W. Coffron.
BE125876-8869-47D0-9583-E39C5E593510.jpeg (280.34 KiB) Viewed 799 times
Mark
by 1024MAK
10 May 2019 00:15
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 226
Views: 17698

Re: Resurrecting an MTX500.

I’ve always found Phil at Retroleum to be quick, if he has an item in stock.

Maybe he had an extended bank holiday weekend...

Mark
by 1024MAK
06 May 2019 22:02
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 226
Views: 17698

Re: Resurrecting an MTX500.

Never mind that, my brain is still trying to work out how Stephen got a cable to go inside the front of his ‘scope. Look, you can see it through the screen! :lol:

Mark