Search found 3629 matches

by 1024MAK
Sat Jun 12, 2021 9:37 pm
Forum: Hardware
Topic: Help with installing a LM386 Module 20 Times Gain Audio Amplifier Module F Raspberry Pi Arduino, on to a ZX board
Replies: 11
Views: 962

Re: Help with installing a LM386 Module 20 Times Gain Audio Amplifier Module F Raspberry Pi Arduino, on to a ZX board

Sorry, it’s hard to tell. Strangely audio amplifier manufacturers don’t design amplifiers or provide specifications for use with 1980s home computers… Can you hear the loading sounds from the internal speaker in the Spectrum that is not loading? If however it’s working fine with one Sinclair compute...
by 1024MAK
Sat Jun 12, 2021 3:38 pm
Forum: ZX BASIC
Topic: Cheryl Ladd on ZX81
Replies: 11
Views: 444

Re: Cheryl Ladd on ZX81

If you have this Cheryl Ladd program for BBC Micro it would be great. Could you check? :D Sorry, you misunderstood what I said (or what I intended to say). If I had known about the radio broadcast, then I may have recorded the BBC Micro programs, but I did not know about it, hence I did not record ...
by 1024MAK
Sat Jun 12, 2021 11:13 am
Forum: ZX BASIC
Topic: Cheryl Ladd on ZX81
Replies: 11
Views: 444

Re: Cheryl Ladd on ZX81

Good luck with your hunt. As well as home computer programs being broadcast via radio stations, some of the U.K. television stations also broadcast home computer programs. I remember Channel Four broadcasting ZX Spectrum programs via the TV audio in a show on I think Sunday mornings. One problem is ...
by 1024MAK
Fri Jun 11, 2021 11:33 am
Forum: Development
Topic: Let's talk about Hi-Res truth and myths, I'm angry.
Replies: 2
Views: 205

Re: Let's talk about Hi-Res truth and myths, I'm angry.

OK, I'm a little angry. I was eager to do some hi res experiment on my ZX81 and all I hear is that you only can do it with no memory extension or with a modified one. Not entirely true. The Sinclair 16k RAM pack and most third party RAM packs need modification for ‘true hi-res’ graphics. But most <...
by 1024MAK
Sun Jun 06, 2021 1:14 am
Forum: Hardware
Topic: How is the onboard RAM deactivated?
Replies: 7
Views: 378

Re: How is the onboard RAM deactivated?

If you look at the topic I linked to earlier (here’s another link ), RAM address decoding is discussed. In most low cost designs, /RAS for the DRAM chips is derived from a very slightly delayed /MREQ signal. Then after a further delay, the multiplexer control changes state, putting the remaining par...
by 1024MAK
Sun Jun 06, 2021 12:00 am
Forum: Hardware
Topic: How is the onboard RAM deactivated?
Replies: 7
Views: 378

Re: How is the onboard RAM deactivated?

I think I understand. So the slot RAMCS' is effectively between ULA and R2? Is that what the apostrophes mean, which "half" (which side of the resistor) the lines are on? If it's a straight connection to 5V on the 16k pack, that means it cannot snoop RAMCS' though. So is it purely looking at the ad...
by 1024MAK
Sat Jun 05, 2021 10:51 am
Forum: Hardware
Topic: How is the onboard RAM deactivated?
Replies: 7
Views: 378

Re: How is the onboard RAM deactivated?

Hello and welcome :D

In the 16k RAM pack, it’s a straight connection between +5V and /RAMCS’ (edge connector pin 2A). On the ZX81/TS1000 board, this is on the SRAM side of resistor R2, hence overrides the ULA /RAMCS signal on IC1 pin 12 but without damaging the ULA output pin circuitry.

Mark
by 1024MAK
Fri Jun 04, 2021 6:47 pm
Forum: SALES
Topic: Lardo buys another zeddy
Replies: 117
Views: 59488

Re: Lardo buys another zeddy

Of course it had to be the National Semiconductor MM5290N-2 that I did not list :lol:

These are similar to the 4116 DRAM chips in that they also need three separate supply voltages.

Mark
by 1024MAK
Fri Jun 04, 2021 3:32 pm
Forum: SALES
Topic: Lardo buys another zeddy
Replies: 117
Views: 59488

Re: Lardo buys another zeddy

I have a soft spot for those Stonechip memory packs, more reliable than Clive's offerings in my opinion. They use a different memory chip to the Sinclairs(Mark will know which ones) and if you pop the back cover off (clip on on not screwed) there should be a set of clips that take a 16k module whic...
by 1024MAK
Thu Jun 03, 2021 9:40 am
Forum: Hardware
Topic: ZX81 Troubleshooting
Replies: 8
Views: 871

Re: ZX81 Troubleshooting

Voltage reg outputting 4.9V So far all of the Z80 test pass with the scope showing exactly what you described There is activity on A14/15 and A0-13 D2 and D6 are not very active only tiny blips on the scope. The other data lines show activity. The SRAM is labelled MOSTEK MK4118N-4 8037 I tried with...