Search found 2892 matches

by 1024MAK
Sun May 31, 2020 10:20 am
Forum: Hardware
Topic: I think I killed her.. :_(
Replies: 3
Views: 81

Re: I think I killed her.. :_(

I don't know much about this machine, but if you shorted pins on a power transistor or regulator and one pin was the unregulated input and the other pin was the regulated output (+5V for TTL computer logic supply), even a briefly, it causes an over-voltage on the regulated supply. Some chips when op...
by 1024MAK
Sat May 30, 2020 11:08 pm
Forum: Hardware
Topic: ZX80 Jumper A - B or A - C, purpose?
Replies: 6
Views: 166

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

Take some good quality photos from various angles before you disconnect or remove it.

Mark
by 1024MAK
Sat May 30, 2020 11:06 pm
Forum: Hardware
Topic: I think I killed her.. :_(
Replies: 3
Views: 81

Re: I think I killed her.. :_(

If you have two RAM chips that are the same age and type and one is getting very hot, renew it.

If however it is just slightly warmer than the other one, it may be okay.

Mark
by 1024MAK
Sat May 30, 2020 10:23 am
Forum: Hardware
Topic: microdrive head
Replies: 2
Views: 79

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: 6
Views: 166

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: 6
Views: 166

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: 6
Views: 183

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: 370

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: 370

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: 370

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...