Search found 2365 matches

by 1024MAK
Tue Jul 16, 2019 10:31 am
Forum: Hardware
Topic: Issue 3 Spectrum 48k no display no boot nothing
Replies: 2
Views: 37

Re: Issue 3 Spectrum 48k no display no boot nothing

Hello Ziggy and welcome :D Im using a DC-DC converter set at 9v. When I powered it up (around 450MA draw) there was no display. I went ahead and done the composite mod with capacitor, to rule out TV, same thing no display , the voltages at the DRAMS 4116 -5V +12V +5V are ok. I trust that your power ...
by 1024MAK
Mon Jul 15, 2019 5:02 pm
Forum: Sinclair Misc
Topic: Alan Turing to appear on new £50 note
Replies: 3
Views: 66

Alan Turing to appear on new £50 note

Alan Turing to appear on new £50 note Quoting RetroTechie from World of Spectrum forums : Great when a giant of science & technology is honored this way: https://www.bankofengland.co.uk/news/2019/july/50-pound-banknote-character-announcement Just for laughs, they should wait until the note is 6-12 m...
by 1024MAK
Sun Jul 14, 2019 10:44 pm
Forum: Hardware
Topic: EPROM models for 8K ZX80 ROM
Replies: 2
Views: 80

Re: EPROM models for 8K ZX80 ROM

The socket in a ZX80 is a 24 pin DIL type designed for ROMs like/similar to the TMS4732 or D2364C (see here for a pin-out). The only EPROM that is close to being compatible is the TMS2532 (but these are only 4K bytes). This does not matter if you only want the 4K bytes ZX80 ROM. Most 8K bytes EPROMs...
by 1024MAK
Sun Jul 14, 2019 8:14 pm
Forum: Hardware
Topic: Jailbars on ZX80
Replies: 4
Views: 139

Re: Jailbars on ZX80

Assuming that the existing electrolytic capacitor in the external PSU is okay (if a Sinclair type), and the 7805 voltage regulator is okay, then it is just digital noise due to the use of low value decoding capacitors. The other Sinclair computers of the time (ZX81 and ZX Spectrum) also suffer a sim...
by 1024MAK
Sat Jul 13, 2019 6:19 pm
Forum: Hardware
Topic: Interference in Composite
Replies: 2
Views: 43

Re: Interference in Composite

The ZX Spectrum uses 4116 DRAM chips for the ‘lower’ RAM, part of which is the video memory. These actually run from a +12V DC supply. They also require a -5V bias supply. Hence the ZX Spectrum PCB has a DC-DC converter circuit. If the electrolytic capacitors have aged or dried out, this may well ca...
by 1024MAK
Sat Jul 13, 2019 4:45 pm
Forum: Hardware
Topic: Data interface on ZX
Replies: 2
Views: 55

Re: Data interface on ZX

The Sinclair Interface 1 includes a bit-bashed serial port. It uses a 9 pin D-connector, but with non-standard pin-out. SPECTRA also includes an Interface 1 compatible serial port. If you want a DIY system, the difficulty is the range of UART serial chips is rather limited these days. Zilog’s versio...
by 1024MAK
Sat Jul 13, 2019 4:31 pm
Forum: Hardware
Topic: Identifying Board Version
Replies: 3
Views: 99

Re: Identifying Board Version

The position of the heatsink only tells you if it is an issue 1 or issue 2 (not above the edge-connector) or is an issue 3 or later. Issue 5 and issue 6A boards use a second 40 pin glue chip instead of smaller 74LSxxx chips to control the “upper” 32K RAM, these are visible so you can distinguish bet...
by 1024MAK
Thu Jul 11, 2019 11:24 pm
Forum: SALES
Topic: Timex Sinclair 1000 with 64K
Replies: 1
Views: 110

Re: Timex Sinclair 1000 with 64K

Times Sinclair 1000 with 64K on Ebay ( item # 273916650306 ) Hi Aurelbois Welcome to our forum. Is this your eBay listing, or just one that you spotted? Although these RAM packs do contain 64K bytes of RAM, unless there is some bank switching arrangement, it is only possible to use 56K bytes of the...
by 1024MAK
Thu Jul 11, 2019 11:17 pm
Forum: Hardware
Topic: ZX80 from NTSC to PAL?
Replies: 3
Views: 151

Re: ZX80 from NTSC to PAL?

if I understand well, if D11 is present, the ZX81 is ready for NTSC (USA) while, if D11 is NOT present, the ZX81 is ready for PAL (EU), right? I presume you meant to say ZX80? But yes, if D11 is fitted, it is set up for use in the U.S.A., if D11 is not fitted, it is a U.K. / Europe model. Only this...
by 1024MAK
Wed Jul 10, 2019 10:08 am
Forum: Hardware
Topic: ZX80 from NTSC to PAL?
Replies: 3
Views: 151

Re: ZX80 from NTSC to PAL?

On both the ZX80 and the ZX81, the display is generated by the Z80 CPU following the instructions from either the ROM code (the firmware, the normal BASIC system) or from RAM (for example, a loaded high resolution program). In a ZX81, the ULA does have an input pin, whereby a resister (R30) is fitte...