Search found 1113 matches

by Paul
Thu Dec 03, 2020 6:54 pm
Forum: Development
Topic: New prototype ZX-deluxe+
Replies: 11
Views: 178

Re: New prototype ZX-deluxe+

zxhenk wrote: Thu Dec 03, 2020 6:13 pm So only kits or completly build.
So, I'm not interested :ugeek:
by Paul
Thu Dec 03, 2020 4:40 pm
Forum: Development
Topic: New prototype ZX-deluxe+
Replies: 11
Views: 178

Re: New prototype ZX-deluxe+

zxhenk wrote: Thu Dec 03, 2020 12:04 pm The ZX-deluxe is in its prototype stage and I was wondering if there are others who would be interested in this design.
I am very interested in a PCB only. I have the MX switches, keys, wiznet etc.
Please PM me about the conditions.
Kind regards Paul
by Paul
Thu Nov 26, 2020 12:20 pm
Forum: Development
Topic: ZX21 Project ZX81 Replacement PCB
Replies: 26
Views: 1038

Re: ZX21 Project ZX81 Replacement PCB

To limit RAMTOP isn't sufficient. You need the correct RAM-Shadows as well. Which means you have to disconnect the unused RAM addresslines and use pull-ups or pulldowns instead.
by Paul
Thu Nov 26, 2020 5:51 am
Forum: WANTED
Topic: Wanted alphacom 32 power supply
Replies: 14
Views: 3056

Re: Wanted alphacom 32 power supply

Yes it does work with 24 volt as well.
See https://forum.tlienhard.com/phpBB3/view ... 587#p45587
by Paul
Thu Nov 26, 2020 5:36 am
Forum: Development
Topic: ZX21 Project ZX81 Replacement PCB
Replies: 26
Views: 1038

Re: ZX21 Project ZX81 Replacement PCB

Is there much software that needs more than 32K? There is no commercial Software I know of that uses more than 32K of RAM There is quite some commercial Software that formerly used an EPROM in the 8-16 K area that can be used in RAM at the same place. That's why ZXPand can select the 32K beeing fro...
by Paul
Wed Nov 25, 2020 4:57 pm
Forum: Development
Topic: ZX21 Project ZX81 Replacement PCB
Replies: 26
Views: 1038

Re: ZX21 Project ZX81 Replacement PCB

fordp2002 wrote: Wed Nov 25, 2020 12:52 pm Which RAM chip would you propose for 56K?
For example AS 6C1008-55PCN or 628128.
I also like small dil32 cache chips.
Dip-32 Retro IS61C512-20N
by Paul
Wed Nov 25, 2020 12:20 pm
Forum: Development
Topic: ZX21 Project ZX81 Replacement PCB
Replies: 26
Views: 1038

Re: ZX21 Project ZX81 Replacement PCB

I looked at your schematic.
You state ULA 2C210E which has a backporch and add a backporch to it.
Is the additional backporch optional for 2C184 ULA?
Also you add a 32k RAM, why not 56K? Will it be possible to jumper to 1K, 2K, 16K, 32K?
You seem to use ULA /RAMCS which means 16 only.
by Paul
Thu Nov 19, 2020 8:45 am
Forum: Hardware
Topic: Trying to make a 32K mod on Zx81 together with other mods
Replies: 2
Views: 220

Re: Trying to make a 32K mod on Zx81 together with other mods

A13 to Pin 3 is needed for extended memory configurations.
Indeed with vla81 it's better to connect it directly instead with zx8-ccb.
by Paul
Wed Nov 11, 2020 6:21 am
Forum: Hardware
Topic: Flaky ZX81
Replies: 31
Views: 899

Re: Flaky ZX81

Because ZXPand extends the power on reset. Just as my earlier proposed larger reset capacitor does.
See second post in this thread.
by Paul
Sun Nov 08, 2020 8:28 am
Forum: Hardware
Topic: How to power off the ZX81 correctly
Replies: 15
Views: 392

Re: How to power off the ZX81 correctly

I have a switch at the 230V line. If a "not so good" power supply is used without load it can go quite high with the voltage. Then the "stress" to the Zeddy (and extensions) 5V circuit is higher than necessary. Building up the transformer voltage with the Zeddy plugged in (having a load) these peaks...