Topic: MTX REMEMOrizer  (Read 4722 times)

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Offline Andy Key

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MTX REMEMOrizer
« on: October 20, 2012, 11:14:06 PM »
REMEMOrizer is an add-on for Memotech computers which I have designed and built a working prototype.
It provides memory upgrade (if you need it), extra memory (to use as RAM Disc), SD Card as disk, CP/M support, 80 column card (outputs to VGA) and virtual tape support.

Basically, it loads games in seconds...

Its very nearly ready, and I expect I'll end up making a small number of them for enthusiasts, which I'll make available at component cost price.

http://www.nyangau.org/rememorizer/rememorizer.htm
http://www.nyangau.org/memotech/memotech.htm

{{{ Andy

Offline AndyRCM

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Re: MTX REMEMOrizer
« Reply #1 on: October 20, 2012, 11:16:12 PM »
Nice work Andy - please do put RCM down for one please? :)
"I could see the faces of those who led pissing themselves laughing" - Funeral Pyre by The Jam

Offline questor

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Re: MTX REMEMOrizer
« Reply #2 on: October 21, 2012, 10:39:24 AM »
I like it....
Now if we could also fix our other MTXs (the ones with the display issues) we could have some spare working machines!

Offline Andy Key

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Re: MTX REMEMOrizer
« Reply #3 on: October 24, 2012, 12:39:11 AM »
What are the symptoms?
Black screen? Green screen? Blue screen? Tearing? Corrupt characters?
Humming noise? Silent?

My site has the Service Manual for download.
MTX Operators Manual has full schematics at the back.

Done any investigation inside the case?
Having an oscilliscope helps quite a lot, even if its one of those cheap ones.
Tried piggybacking known good ICs on top of suspect ones?
Got any spare 4116s to try on top of video memory chips?
Any particular components getting very hot?
Z80 and TMS9929 video chip will be hot, but not scalding.
Is R60 (resistor just above ROMs on bottom right) scaldingly hot?

{{{ Andy

Offline Panther

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Re: MTX REMEMOrizer
« Reply #4 on: October 24, 2012, 07:47:42 AM »
I know Phu tried repairing one of RCM's and Porchy looked at mine, as far as I know both had problems finding a repair solution.

Perhaps Phu can best describe the issue ?

Offline Phu

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Re: MTX REMEMOrizer
« Reply #5 on: October 24, 2012, 02:19:40 PM »
The fault we keep getting is a banding problem on the video output. A wide band moves down the screen at a steady rate. It starts off as a mild distortion, but as the machine is left on longer it turns into a solid black/grey/white band that starts interfering with sync levels and destabilising the picture.

Generally speaking, it affects the U and V outputs coming from the TMS9929, but not the Y output.

I checked all the power inputs and they are solid flat, so it's not a "wobbly" power issue. I did look at the dry capacitor approach, but the only electrolytics are the power supply caps and they seem fine (flat DC on all lines).

-- Richard
8 End of File, RCM:1

Offline Andy Key

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Re: MTX REMEMOrizer
« Reply #6 on: October 24, 2012, 11:08:40 PM »
Tried an alternative TMS9929A?
Tried swapping video daughter cards?
If you remove the daughter card, power up and leave the system to
warm up for long enough for problem to have shown (if you had still had the daughter board connected), do you still see problems with the U and V outputs from the TMS9929A?
4116 VRAMs getting hot?

In related news, I also have an MTX with dodgy video.
I found it possible to pick up a spare TMS9929A (eBay or retro IC eeb
site, I forget where).
In my case, I currently suspect the 4116 VRAMs, as swapping TMS9929As didn't help, and these ICs need strange voltage lines, one of which I think are drawing a lot of current.

{{{ Andy

Offline Phu

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Re: MTX REMEMOrizer
« Reply #7 on: October 27, 2012, 01:19:13 PM »
Tried an alternative TMS9929A from another MTX... no difference.
Distortion visible on oscilloscope with no daughterboard.
4116 VRAMS are warm, but I wouldn't have said they were hotter than expected.

Could be one to replace 4116s on... fortunately RCM recently acquired a small pile of these.

Unfortunately, they are not candidate for replacement for e.g. 4464s (single supply/a quarter of the chips) or static RAMs, due to the peculiar D/Q access the TMS9929 uses.

-- Richard
8 End of File, RCM:1

Offline Andy Key

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Re: MTX REMEMOrizer
« Reply #8 on: November 02, 2012, 05:33:55 PM »
@AndyRCM

I'm ready to ship.
Because my shipment of GALs from Taiwan seems to have gone astray, I now need to know what kind of MTX you will be connecting to.

MTX500?
PRINT PEEK(64122) = 0
motherboard probably has 8 4132 DRAMs or equivalent
might have half-working 4164s, but only use half of them

MTX512?
PRINT PEEK(64122) = 1
motherboard has 8 4164 DRAMs or equivalent
might actually be an MTX500 with 32KB extra memory on an expansion card

MTX512 S2?
PRINT PEEK(64122) = 1
motherboard has 8 4256 DRAMs, and yellow wires on the back)
rare

Something else?
Let me know

Also, I am assuming I should send to RCM address.

Let me know...

{{{ Andy

Offline AndyRCM

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Re: MTX REMEMOrizer
« Reply #9 on: November 02, 2012, 05:37:39 PM »
Hi Andy,
I will check the MTX on Sunday (out all day tomorrow) . . . and let you know.
I will send you a PM with my address details.
Cheers
Andy
"I could see the faces of those who led pissing themselves laughing" - Funeral Pyre by The Jam

Offline porchy

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Re: MTX REMEMOrizer
« Reply #10 on: November 02, 2012, 06:51:35 PM »
whats GAL's do you require Andy?

Offline Andy Key

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Re: MTX REMEMOrizer
« Reply #11 on: November 03, 2012, 09:51:15 AM »
I had originally planned to supply each REMEMOrizer with each of the possible GALs the user might need (GALs are needed for MTX500 or MTX512 S2 only).

So I ordered a cheap job lot, which ends up being shipped by carrier pigeon and donkey from Taiwan.

As most people have MTX512 and don't need a GAL, my new plan is to ship without and ask people to let me know if they need one.
I do have a couple, just not enough to send everyone 3 on the off-chance they might need one.

And of course, the .eqn files are on the website, so an impatient customer with PAL/GAL programmer and PAL/GALs can make their own quicker than the postal service.

{{{ Andy

Offline Andy Key

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Re: MTX REMEMOrizer
« Reply #12 on: November 12, 2012, 09:28:12 PM »
I wonder whether AndyRCM has received and tried his REMEMOrizer yet?

{{{ Andy

Offline AndyRCM

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Re: MTX REMEMOrizer
« Reply #13 on: November 12, 2012, 09:29:45 PM »
Received mate - not had chance to try yet though - but will soon . . . :)

"I could see the faces of those who led pissing themselves laughing" - Funeral Pyre by The Jam

Offline Andy Key

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Re: MTX REMEMOrizer
« Reply #14 on: November 25, 2012, 08:59:45 AM »
Tried it yet?

{{{ Andy