Search found 239 matches

by stephen_usher
Sun May 12, 2019 10:02 pm
Forum: Terriblefire's channel
Topic: Logic Analyser Died
Replies: 12
Views: 291

Re: Logic Analyser Died

:-(
by stephen_usher
Sun May 12, 2019 11:07 am
Forum: 8 BIT CORNER
Topic: My next challenge: Memotech MTX500.
Replies: 23
Views: 543

Re: My next challenge: Memotech MTX500.

P.S. It's so nice to have this working again after 31 years!

Here's the same machine back in 1985. :-)
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by stephen_usher
Sun May 12, 2019 11:01 am
Forum: 8 BIT CORNER
Topic: My next challenge: Memotech MTX500.
Replies: 23
Views: 543

Re: My next challenge: Memotech MTX500.

PhilC wrote:
Sun May 12, 2019 9:47 am
Well done Stephen. Very happy to see you bought it back to life.
Must get myself one at some point.
As with most things, they're going for silly money on eBay, and there's no guarantee that they even work!
by stephen_usher
Sun May 12, 2019 11:00 am
Forum: Terriblefire's channel
Topic: Logic Analyser Died
Replies: 12
Views: 291

Re: Logic Analyser Died

OK, so what's the third thing to go wrong?
by stephen_usher
Sun May 12, 2019 8:37 am
Forum: 8 BIT CORNER
Topic: My next challenge: Memotech MTX500.
Replies: 23
Views: 543

Re: My next challenge: Memotech MTX500.

I found a hack to allow 4164 RAM chips to replace 4116 RAM and replaced the faulty VRAM chip and, success! IMG_1459.jpg I now just have to wait for a replacement 74LS273 as the dead flip-flop stops part of the keyboard scan from working. Then I've got to see if I can stop a lot of the keys on the ke...
by stephen_usher
Sat May 11, 2019 7:15 pm
Forum: 8 BIT CORNER
Topic: My next challenge: Memotech MTX500.
Replies: 23
Views: 543

Re: My next challenge: Memotech MTX500.

I had a breakthrough on this project today. Having traced the ROM select problem back to one of the flip-flops in a 74LS273 I swapped this over and suddenly the machine came to life, well mostly. The PAL video adapter board was still shot and it was obvious from the display that at least one of the ...
by stephen_usher
Fri May 10, 2019 9:31 am
Forum: Terriblefire's channel
Topic: Logic Analyser Died
Replies: 12
Views: 291

Re: Logic Analyser Died

That's annoying. How easy are those particular DS units to find? Some of the older ones are still available but the newer ones discontinued (a problem for those trying to keep Sun Ultra workstations running, but older SPARCstations are just fine as the 42T02 is still in manufacture). Given how often...
by stephen_usher
Thu May 09, 2019 3:44 pm
Forum: 8 BIT CORNER
Topic: My next challenge: Memotech MTX500.
Replies: 23
Views: 543

Re: My next challenge: Memotech MTX500.

Oh, I forgot to add that I'm having to fix the PAL video daughter board after the 'scope probe ground wire crocodile clip jumped off the modulator shield I was using as the ground and bounced over the solder side of the board. Now the display doesn't sync properly. Hopefully it's not the 1889 chip a...
by stephen_usher
Thu May 09, 2019 2:07 pm
Forum: 8 BIT CORNER
Topic: My next challenge: Memotech MTX500.
Replies: 23
Views: 543

Re: My next challenge: Memotech MTX500.

Well, I'm still working on this. After at one point somehow getting 12V on a couple of address lines (I have no idea how to this day as there are no shorts) I've had to replace the CPU, Z80 CTC and many of the other LS chips. Still no go. I've possibly traced the problem down to the PAL chip which g...
by stephen_usher
Tue Apr 23, 2019 6:53 pm
Forum: CHAT FORUM
Topic: Obtained today...
Replies: 2
Views: 115

Obtained today...

Today I visited my friends Chris and Meriel who have been known to horde old computer componets... So I picked up 32 64Kx1 chips, some SIMMs, four Z80Bs and three 68000s...
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