Search found 563 matches

by 1024MAK
12 Jul 2019 19:17
Forum: GENERAL DISCUSSIONS
Topic: MTX on the road.
Replies: 6
Views: 285

Re: MTX on the road.

👍 👏 8-) :D

Mark
by 1024MAK
07 Jul 2019 19:32
Forum: GENERAL DISCUSSIONS
Topic: MTX 512 (debugging thread)
Replies: 48
Views: 2174

Re: MTX 512 (debugging thread)

The key-switches used suffer from similar problems to the keyboard switches as used on Acorn Electrons, BBC Micros and BBC Masters. The contacts inside become dirty, or a thin layer of oxide forms on the contacts. This results in either, the contacts not making electrical contact, or making intermit...
by 1024MAK
07 Jul 2019 09:15
Forum: NEW HARDWARE
Topic: ROTT 1600
Replies: 1
Views: 256

Re: ROTT 1600

Or ROTTon name :lol:

Good luck with testing :D

Mark
by 1024MAK
24 Jun 2019 15:37
Forum: PROGRAMMING
Topic: Bootstrap and boot blocks
Replies: 99
Views: 3291

Re: Bootstrap and boot blocks

I’m watching this with great interest :mrgreen:

Mark
by 1024MAK
23 Jun 2019 14:30
Forum: GENERAL DISCUSSIONS
Topic: MTX 512 (debugging thread)
Replies: 48
Views: 2174

Re: MTX 512 (debugging thread)

As the supply voltages on the 4116 DRAM chips are present and correct, then a failure of one or two of the 4116 DRAM chips is the most likely cause (assuming there is no PCB track damage). So I would not worry about looking for a short circuit on J12, as clearly no supplies are in short. Have we giv...
by 1024MAK
15 Jun 2019 15:54
Forum: GENERAL DISCUSSIONS
Topic: MTX 512 (debugging thread)
Replies: 48
Views: 2174

Re: MTX 512 (debugging thread)

4116 DRAM chips contain 16384 memory locations. But only one bit wide. Hence in the data sheet it says the chip is a 16384 bit memory. But we need the data width to be 8 bits wide (one byte), so eight DRAM chips are needed, each DRAM chip supplies one bit of the eight bit byte. Total memory will the...
by 1024MAK
15 Jun 2019 15:30
Forum: GENERAL DISCUSSIONS
Topic: MTX 512 (debugging thread)
Replies: 48
Views: 2174

Re: MTX 512 (debugging thread)

Piggy backing only works sometimes, and not very often. So I think it is not a very reliable method of testing. The problem is that DRAM chips are very complex devices and there are countless ways that they can fail. If the original fitted chip decides to output a logic low at the same time that the...
by 1024MAK
19 May 2019 16:05
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 226
Views: 10541

Re: Resurrecting an MTX500.

If the resistor is getting hot, yep, a new TIP2955 is needed.

Mark
by 1024MAK
19 May 2019 15:08
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 226
Views: 10541

Re: Resurrecting an MTX500.

Sometimes the people copying / writing the descriptions and specifications on the suppliers web site / catalogues don’t fully understand the datasheet. And sometimes the datasheets are misleading. The voltages and currents of PNP transistors are opposite compared to NPN transistors, so are normally ...
by 1024MAK
18 May 2019 23:56
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 226
Views: 10541

Re: Resurrecting an MTX500.

CMOS devices designed to work with 5V TTL systems should be okay with logic one/high levels of 2V and greater. So all the Zilog Z80 series CMOS devices, 74HCTxxx chips and all compatible EPROM, EEPROM and SRAM chips. However with modern EEPROM and SRAM chips, it’s best to double check with the data ...