Search found 2369 matches

by 1024MAK
Thu Jul 18, 2019 12:22 pm
Forum: Sinclair Misc
Topic: Why did Sinclair resist Floppy drives for it's computers ?
Replies: 3
Views: 96

Re: Why did Sinclair resist Floppy drives for it's computers ?

Sir Clive had a thing about continuous tape loop systems, hence he developed the Microdrive. It was intended that out of the box, ZX Spectrum computers would have built in support for his Microdrive system. All the user/owner would have to do, would be to buy a Microdrive. Unfortunately, the Microdr...
by 1024MAK
Wed Jul 17, 2019 7:21 pm
Forum: Hardware
Topic: 2732 to 2532 adaptation
Replies: 5
Views: 132

Re: 2732 to 2532 adaptation

Lift the VPP pin clear of the socket so it no longer makes contact with the socket. Then connect the VPP pin to +5V. Connect A11 to A11. Connect /E to PD. As per your diagram above. A12 being unconnected does not make any difference. All that will happen, is that the 4K bytes of the EPROM will appea...
by 1024MAK
Tue Jul 16, 2019 10:48 pm
Forum: Hardware
Topic: 2732 to 2532 adaptation
Replies: 5
Views: 132

Re: 2732 to 2532 adaptation

On the board, which enable pin is actively used, pin 18 or pin 20 on the 2732? Or are both used?
Only, some ROM chips and the 2532 only have one enable pin.

And yes, the A11 line needs swapping.
Connect VPP to +5V.

Mark
by 1024MAK
Tue Jul 16, 2019 7:18 pm
Forum: Hardware
Topic: Issue 3 Spectrum 48k no display no boot nothing
Replies: 4
Views: 128

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

Hi Ziggy All those voltages are good :D Now test on pin 32 of the ULA (IC1). This signal, if present will be a lower amplitude signal and the waveform is not very sharp. So I hope that your logic analyser can pick it up. Again, it is a 3.5MHz frequency. Ideally an oscilloscope is better for this tes...
by 1024MAK
Tue Jul 16, 2019 10:31 am
Forum: Hardware
Topic: Issue 3 Spectrum 48k no display no boot nothing
Replies: 4
Views: 128

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: 114

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: 99

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: 155

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: 52

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: 63

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...