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For those members that want to replace missing, damaged or corroded MTX case screws, here are the details of suitable replacements :D The original type are M3 thread size, black, 8mm long socket button head machine screws. Replacement 8mm screws are a bit hard to get. But on most machines, 10mm long...

:arrow: Do members like the colour scheme of the forum? :?: Is the red coloured text okay for you? :?: Do you think that having a black background with red and with white coloured text is easy or hard to read? :?: :idea: Let's have your comments :mrgreen: Mark PS if there is any other area that you ...

Note that the following images are large. Modified 3 ROM 4000-05 PCB top http://farm8.staticflickr.com/7422/9951691073_77ec39ddaa_o.jpg Modified 3 ROM 4000-05 PCB bottom http://farm6.staticflickr.com/5477/9951704173_1ddd6dbcfc_o.jpg Modified 3 ROM 4000-05 PCB bottom close-up http://farm4.staticflick...

While working on a faulty MTX board at Memofest 2013 (yesterday, Saturday 21st September), we were confronted with an unfamiliar EPROM chip. The chip was type 25P64 as shown in this picture. photo 25P64 (p).JPG A quick search of the web for the data sheet was unsuccessful. However, a data sheet for ...

It still looks like a failure of the power transistor Q4 TIP2955. I will post a simple test circuit for testing TIP2955 transistors "out of circuit" later today ;-) Mark :oops: Oops, I never did remember to post up this circuit. Never mind :roll: Anyway, to close out the power issue and t...

Here are some useful information sources:-

Wikipedia - DRAM
Memory Basics
Memory Devices
DRAM TECHNOLOGY
Introduction to DRAM
Z80 INTERFACING TECHNIQUES
1984 MOS Memory Data Book
Understanding DRAM Operation
Ram Guide


Mark

It's all done by special mirrors and dilithium crystals inside the DRAM chips via a RAS hyperlink thread. When the Z80 wants to perform a refresh, via a pulley, it tugs the RAS line and (assuming no snags occur, which would result in a meltdown failure) this tilts the mirror which allows the dilithi...

The video display processor (VDP) chip in MTX machines is a TMS9929. This has it's own 16k byte memory made up of eight 4116 DRAM chips (the video RAM or VRAM). One problem that some users face, is that of the 4116 DRAM (VRAM) chips failing :-(. These are 16k bit DRAM chips that store a single bit a...

Bottom of PCB picture edited and converted to a monochrome image...

Mark

It still looks like a failure of the power transistor Q4 TIP2955.

I will post a simple test circuit for testing TIP2955 transistors "out of circuit" later today

Mark