Oh, you mean just like this then ?
http://www.primrosebank.net/computers/m ... mavram.htm
Resurrecting an MTX500.
Re: Resurrecting an MTX500.
You can also use HM4816 or equivalent DRAM chips...
Mark
Mark
![Exclamation :!:](./images/smilies/icon_exclaim.gif)
![Exclamation :!:](./images/smilies/icon_exclaim.gif)
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
![Exclamation :!:](./images/smilies/icon_exclaim.gif)
Looking forward to summer being good this year
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
Not as many MTXs as Dave!
![Laughing :lol:](./images/smilies/icon_lol.gif)
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Re: Resurrecting an MTX500.
Oh! YesDave wrote: ↑11 May 2019 21:41 Oh, you mean just like this then ?
http://www.primrosebank.net/computers/m ... mavram.htm
![Smile :-)](./images/smilies/icon_e_smile.gif)
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Re: Resurrecting an MTX500.
So, I removed the original chip, fitted a socket and modified a 4164...
Success!
However, it's not reliable. The machine starts up with either a blank screen or corrupted graphics on screen a lot of the time. It's probably due to the 4164 being 150ns RAM and the ITT stuff being a heck of a lot slower (they look like they're 300ns???)
Success!
However, it's not reliable. The machine starts up with either a blank screen or corrupted graphics on screen a lot of the time. It's probably due to the 4164 being 150ns RAM and the ITT stuff being a heck of a lot slower (they look like they're 300ns???)
Re: Resurrecting an MTX500.
There is no problem using faster RAM
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Re: Resurrecting an MTX500.
OK, so I don't know what's causing the issue then.
Anyway, 99% there. Once the new 74LS273 appears on Tuesday hopefully all the keyboard will work. I'm not sure about this one as it came off the machine I fixed a couple of years ago and seemed iffy, so I swapped the keyboards over. Anyway, we'll see.
Anyway, 99% there. Once the new 74LS273 appears on Tuesday hopefully all the keyboard will work. I'm not sure about this one as it came off the machine I fixed a couple of years ago and seemed iffy, so I swapped the keyboards over. Anyway, we'll see.
Re: Resurrecting an MTX500.
That’s good progress
Is the power on reset circuit working okay? It’s formed by R18, D13 and C11 (10uF) on the input to IC 9C (4070B).
Mark
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
Is the power on reset circuit working okay? It’s formed by R18, D13 and C11 (10uF) on the input to IC 9C (4070B).
Mark
![Exclamation :!:](./images/smilies/icon_exclaim.gif)
![Exclamation :!:](./images/smilies/icon_exclaim.gif)
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
![Exclamation :!:](./images/smilies/icon_exclaim.gif)
Looking forward to summer being good this year
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
Not as many MTXs as Dave!
![Laughing :lol:](./images/smilies/icon_lol.gif)
Re: Resurrecting an MTX500.
If the machine previously worked well, then the following may be a red herring, but . . . . .
Have a look at page 46 of the Service Manual available on this page :
http://www.primrosebank.net/computers/m ... anuals.htm
Memotech made a modification to the timing chain circuit to help intermittent start up problems
Probably not needed, but since you have the machine in bits anyway, it might be worth doing
Have a look at page 46 of the Service Manual available on this page :
http://www.primrosebank.net/computers/m ... anuals.htm
Memotech made a modification to the timing chain circuit to help intermittent start up problems
Probably not needed, but since you have the machine in bits anyway, it might be worth doing
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Re: Resurrecting an MTX500.
My machine is from after October 1984 so should already have the modification.
I've just noticed that I need to change Link 7 though!
P.S. Having checked the GAL programming this isn't necessary as that pin is ignored anyway.
I've just noticed that I need to change Link 7 though!
P.S. Having checked the GAL programming this isn't necessary as that pin is ignored anyway.
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- Posts: 326
- Joined: 27 Nov 2016 19:58
Re: Resurrecting an MTX500.
Having had the machine burning in running Andy Key's "Reveal" (loaded from the CFX interface) all afternoon it's been stable.
It smells a bit warm, but that might just be the new components evaporating off the volatiles as they get gently roasted by the power circuitry and VDU.
I hope the switch cleaner I have on order will fix the keyboard switch "chatter" so that I don't have to replace most of the keyboard switches.
It smells a bit warm, but that might just be the new components evaporating off the volatiles as they get gently roasted by the power circuitry and VDU.
I hope the switch cleaner I have on order will fix the keyboard switch "chatter" so that I don't have to replace most of the keyboard switches.