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MTX500 upgrades....

Posted: 14 Aug 2012 19:19
by lezanderson
I recently experimented with selling some MTX500 upgrade kits on ebay, however as we found upgrading the poor old MTX500 to an MTX512 is perhaps not as simple as it first seemed.

My kits , just consisted of 64k x 1 bit DRAMs ( 8 of ) and a GAL16V8. I don't believe anyone yet as successfully upgraded their MTX500. Thus I've renamed my kits.. the 'MTX500' destruction kit... I shan't be selling any more on ebay..

If anyone has successfully upgraded an MTX500 circuit board to MTX512... please leave a comment letting everyone else know how you did it.

Re: MTX500 upgrades....

Posted: 17 Aug 2012 23:12
by AndyKey
My problem was that the board got damaged desoldering the old memory chips.
It may be repairable.
I suspect in general its a hard thing to do.
I think the process itself will work, as I think I understand the hardware itself well enough.

Perhaps another less risky option is to create a new
RAM upgrade board, with a few TTL ICs and an SRAM chip.

{{{ Andy

Re: MTX500 upgrades....

Posted: 17 Aug 2012 23:26
by Dave
I thought that I'd done a good enough job with the removal of the old chips and resoldering the new sockets...... but obviously not! I have not given up though and hope to be able to rescue mine too.

If only I'd known about Andy's hardware/software expertise beforehand, then an add-on board similar to what's in my "real" MTX512 would have been the way to go <sigh>.


Re: MTX500 upgrades....

Posted: 23 Oct 2012 21:59
by Dave

I think this thread is dead, but for the sake of completeness, here is my final update....

I can confirm that I did not damage the board during the upgrade attempt, although I may have had a tiny short between a couple of pins on the new IC sockets at one point. With the sockets installed, new 64k RAM chips fitted and the board board cleaned and checked, the system would not operate with the 64K RAM chips.

However, by removing the RAM, leaving the sockets in place and installing one of Andy's new RAM cards, the MTX now works again, now as an MTX512!

Thanks Andy!


Re: MTX500 upgrades....

Posted: 08 Aug 2014 18:25
by Dave
OK - I lied !

On two counts . . . . .

Firstly, the last post was not my final update :)

Second, I must have damaged the board during the upgrade attempt - as I have now fixed it!

Yes, a successful upgrade using one of Lez's kits and a GAL programmed for me by Andy.

Herewith the evidence - yes, it really is the same machine, now with a fully working 64K of on-board RAM
PAL_in_240.jpg (28.83 KiB) Viewed 3516 times

Full details here : ... pgrade.htm

Re: MTX500 upgrades....

Posted: 08 Aug 2014 22:40
by 1024MAK
Clap, clap, clap (never the right smilie is there...).
Well Done Dave 8-)


Re: MTX500 upgrades....

Posted: 09 Jul 2015 13:40
by lezanderson
After Dave & Martin's successful MTX 500 (64K)RAM upgrade some info for any Newbie wanting to do such an upgrade

To upgrade your MTX 500 to 64K RAM, you will need :

8 x 64k x 1 bit DRAMs these can be found / sourced from various sources the cheapest I saw was : ... 3a9877c42d

A GAL16V8 (Memory decoder) ... 2802e3bdc6

DIL sockets (16pin & 20pin) ... 5b14f932e8 ... 19d530accc

Then follow the instruction (carefully) on Dave's website: ... pgrade.htm