Search found 2066 matches

by 1024MAK
Thu Sep 20, 2018 12:09 am
Forum: Development
Topic: Jupiter ACE Kit /sorry half off-topic! :)/
Replies: 17
Views: 2341

Re: Jupiter ACE Kit /sorry half off-topic! :)/

What is the value of L in the circuit diagram. Thanks Ahh, alas, I don’t know! :lol: It was an inductor that was supplied with the kit. I did work out the value, but have forgotten :oops: However, the value is not critical. Use a type described as a RF choke in an axial “resistor like” form. The DC...
by 1024MAK
Wed Sep 19, 2018 9:38 pm
Forum: Sinclair Misc
Topic: Jupiter ACE (again)
Replies: 7
Views: 101

Re: Jupiter ACE (again)

McKlaud wrote:
Tue Sep 18, 2018 9:55 pm
:geek: Still some issues with sync on my LCD TV but generally I am happy with the outcome. :geek:
Maybe this thread will help ;)

Mark
by 1024MAK
Wed Sep 19, 2018 9:28 pm
Forum: Development
Topic: Jupiter ACE Kit /sorry half off-topic! :)/
Replies: 17
Views: 2341

Re: Jupiter ACE Kit /sorry half off-topic! :)/

If you have read my posts above earlier today, please note that I have extensively edited them to correct some errors, remove some mistakes, and to expand the content so that the posts make more sense. Most benefit from being carried out during construction, as they are more difficult to do after th...
by 1024MAK
Wed Sep 19, 2018 11:17 am
Forum: Development
Topic: Jupiter ACE Kit /sorry half off-topic! :)/
Replies: 17
Views: 2341

Re: Jupiter ACE Kit /sorry half off-topic! :)/

Jupiter ACE - optional modifications Add a /ROMCS signal to the edge connector Needs two 1N4148 diodes and two 1K ohm resistors. Needs two track cuts. One cut through the track coming from pin 15 of the 74LS138 (U29) and the second cut is through the track coming from pin 14 of the same chip. Sorry...
by 1024MAK
Wed Sep 19, 2018 11:08 am
Forum: Development
Topic: Jupiter ACE Kit /sorry half off-topic! :)/
Replies: 17
Views: 2341

Re: Jupiter ACE Kit /sorry half off-topic! :)/

CPU clock transistor and it’s resistors and the Recom DC-DC converter:
by 1024MAK
Wed Sep 19, 2018 10:57 am
Forum: Development
Topic: Jupiter ACE Kit /sorry half off-topic! :)/
Replies: 17
Views: 2341

Re: Jupiter ACE Kit /sorry half off-topic! :)/

Close up photos...

First, the composite video circuitry with the emitter follower amplifier.
by 1024MAK
Wed Sep 19, 2018 10:48 am
Forum: Development
Topic: Jupiter ACE Kit /sorry half off-topic! :)/
Replies: 17
Views: 2341

Re: Jupiter ACE Kit /sorry half off-topic! :)/

When I built the replica kit that I bought from eBay, I had to experiment with the base resistor (R7) for the transistor (Q2) that supplies the clock signal to the CPU. Q2 also ended up being a BC547C. The values in use are: R7 = 68K ohms R8 = 330 ohms C9 = 33pF Rather than fitting a modulator, I us...
by 1024MAK
Mon Sep 17, 2018 1:42 am
Forum: Hardware
Topic: Dead ZX81.
Replies: 10
Views: 322

Re: Dead ZX81.

The ULA chips always run hot. That’s normal. The ULA is also the most likely cause of the failure. The photo you posted, that’s an issue 3 board. It is functionality the same as the earlier issue 1 board (there are no known issue 2 boards in existence). The ULA and Z80 CPU can be swapped between boa...
by 1024MAK
Sat Sep 15, 2018 9:01 pm
Forum: Welcome Area
Topic: Good to be here!
Replies: 12
Views: 649

Re: Good to be here!

:P Addendum... where is everybody? Holiday? No, just distracted... :oops: Hello zxooner :D Welcome to our forum. I would say have a look around, but I suspect you already have :mrgreen: We are very friendly here (well, most of the time), so don't be afraid to ask 'stupid' questions ;) Have fun. Mark
by 1024MAK
Thu Sep 13, 2018 2:56 pm
Forum: Welcome Area
Topic: New Zealand ZX81 programmer
Replies: 6
Views: 165

Re: New Zealand ZX81 programmer

Hello Bukster and welcome to our forum.

Have a good browse around the forum.

There are various members producing new software for ZX81/TS1000 machines (and some even for the ZX80).

We very much welcome new contributions :D

Mark