Search found 2879 matches

by 1024MAK
Sat May 30, 2020 10:23 am
Forum: Hardware
Topic: microdrive head
Replies: 2
Views: 30

Re: microdrive head

A microdrive head should look like a cassette tape head (as that is what it is).

Mark
by 1024MAK
Fri May 29, 2020 7:38 pm
Forum: Hardware
Topic: ZX80 Jumper A - B or A - C, purpose?
Replies: 3
Views: 58

Re: ZX80 Jumper A - B or A - C, purpose?

The A-B / A-C link selects between the normal ZX80 black on white and an inverted white on black display. This is ahead of the mixer that adds the sync. French analogue TV has a different signal polarity compared to PAL and NTSC, hence a transistor is used to invert the video signal after the sync s...
by 1024MAK
Fri May 29, 2020 6:48 pm
Forum: Hardware
Topic: ZX80 Jumper A - B or A - C, purpose?
Replies: 3
Views: 58

Re: ZX80 Jumper A - B or A - C, purpose?

Did it come from France?

Mark
by 1024MAK
Fri May 29, 2020 3:30 pm
Forum: Hardware
Topic: PSU and regulators
Replies: 4
Views: 91

Re: PSU and regulators

Increasing the output voltage of a 7805 using a Zener diode
Increasing the output voltage of a 7805 using a Zener diode
Mark
by 1024MAK
Fri May 29, 2020 7:03 am
Forum: ZX BASIC
Topic: TS1000 error code 2 keeps happening
Replies: 22
Views: 210

Re: TS1000 error code 2 keeps happening

An unexpanded ZX81 or TS1000 operates with a ‘collapsed screen’ (D_FILE) to keep RAM usage to a minimum. When there is plenty of spare RAM (e.g. a 16K byte RAM pack is fitted), the screen (D_FILE) is expanded to full size. The fully expanded screen RAM size is 793 bytes (32x24 + 25 HALTs, almost occ...
by 1024MAK
Fri May 29, 2020 12:28 am
Forum: ZX BASIC
Topic: TS1000 error code 2 keeps happening
Replies: 22
Views: 210

Re: TS1000 error code 2 keeps happening

Alas, an internal RAM upgrade is slightly more complex than just fitting a larger capacity chip. But it’s not difficult. See this post for the relevant links ;-)

Mark
by 1024MAK
Thu May 28, 2020 10:12 pm
Forum: ZX BASIC
Topic: TS1000 error code 2 keeps happening
Replies: 22
Views: 210

Re: TS1000 error code 2 keeps happening

The Sinclair/Timex RAM packs use eight 4116 (or equivalent) one bit x 16K DRAM chips. One physical chip stores one bit of a byte. So to store a whole 8 bit byte, you need eight chips. There are various versions of the Sinclair/Timex RAM packs, the earlier version uses two circuit boards and multiple...
by 1024MAK
Thu May 28, 2020 9:29 pm
Forum: Hardware
Topic: PSU and regulators
Replies: 4
Views: 91

Re: PSU and regulators

Yes you can use a 7808 voltage regulator to drop the voltage down, then feed it to the computer. Only third party RAM packs that use the 4116 or equivalent DRAM chip need the +9V rail to be at around 11V. All others should be fine with a lower voltage on the +9V rail. Rather than a hard to get 7808,...
by 1024MAK
Wed May 27, 2020 8:47 pm
Forum: Hardware
Topic: Controlling relays from exp port, I/O.
Replies: 3
Views: 148

Re: Controlling relays from exp port, I/O.

I work the address out to be 0x3FE1 or 16353 decimal.

On a ZX Spectrum address line A0 has to be high (1) otherwise the ULA will respond. Hence 0x3FE1 or 16353 decimal.

Mark
by 1024MAK
Wed May 27, 2020 6:02 pm
Forum: Hardware
Topic: Controlling relays from exp port, I/O.
Replies: 3
Views: 148

Re: Controlling relays from exp port, I/O.

As you are asking the question in relation to a ZX Spectrum, I have moved this to the ZX Spectrum hardware area. On a ZX Spectrum, use: OUT a,d Where a is the address the interface is mapped to, and d is the data byte you want sent to it. Both are in decimal. See the manual for more information. To ...