Recent posts

#1

Technical support - Hardware related / Re: CPC 6128 - white screen, b...

Last post by Bryce - Yesterday at 22:48

That is what you can get for that price and it is on the low end of usable, however still massively better than a multimeter for digital cirquits. You can actually see what the lines are doing (up, down etc). And exact timing (e.g. fractions of a µs) is not important here.

Also the next better suited would be a proper oscilloscope like the Rigol 1054z (or any other entry level brand and model). But you know, it is even used for 200-300€ .. So I did not recommend it here, but that would be actually my normal recommendation to get into an Oscilloscope.

Nowadays you can get the new Rigol DHO800 series, with the DHO804 the cheapest option. That goes for ~400 Euros. This is a huge upstep with 12bit resolution vs 8bit of the old Rigol and 100Mhz vs. 50Mhz.

Hi. I do appreciate the suggestion of the ZT-702S/ZT-703S. I'm just clueless regarding what level of oscilloscope is sufficient for this kind of work.

So I was a little disheartened to be told that the ZT-702S isn't really up to the job of helping to diagnose the issue here, after buying it for that purpose.

I've requested a return on the ZT-702S. Hopefully that will work out and I can spend the money on a Dandanator instead.

I can also almost hear the shouts of "replace the damn RAM chips" and to be honest it does regularly cross my mind to do this, but I would love for a positive confirmation via McArti0'd tests before desoldering anything.

I hope the above doesn't sound too ungrateful! Thanks again for taking the time to reply here.

No issue. I won't shout anything  . It's your machine and it's your decision how you want to fix it. If you intend always using your Scope where a computer is nearby, there are some very good USB Scopes around, that will give you a lot more bandwidth and all the features for under €200.

You can get a Hantek PC 6074BC  (4 Channel 70MHz USB Scope) for €180.

Bryce.

#2

Amstrad CPC hardware / Re: Designing and building the...

Last post by McArti0 - Yesterday at 20:26

A pair of big SRAM chips sounds more practical, these days.

What I mean more is two banks of internal memory larger than 64kB

#3

B

Amstrad CPC hardware / Re: Designing and building the...

Last post by Benedikt - Yesterday at 20:04

Building the GA in TTL logic like the KC compact did will overcome this topic.

And it makes pixel generation (almost) trivially expandable in some ways.

For instance, I would like to give the machine a 256 color hardware palette, and perhaps the possibility to select several variants of that hardware palette.
The KC compact's circuitry can be trivially expanded to 64 colors – it uses two bits per primary color – and most of the pixel generation data path is eight bits wide, already.

Since the KC compact's design uses SRAM chips for the palette entries, we could also add a line counter and implement separate palettes per scan line.
The rationale is that the smallest "modern" parallel SRAM chips have 8 KiB, anyway, and only using the first 16 bytes of 8 KiB would be a huge wasted opportunity.

The addition of video modes with doubled bit depth will be more involved, because the data path to the system RAM has to be widened to 16 bit, but the actual pixel generation should be simple.

All of the above would result in e.g. a "mode 1" variant with 320x200 pixels and 256 colors on screen, namely with a 16 color palette per scan line.
A true 256 color mode would also be possible, namely as "mode 0" that uses two RAM pages in parallel.

I also really want to squeeze in an attribute mode for colorful high-res "text modes", ideally with a backwards compatible RAM page for 1 bpp graphics and another RAM page for color attributes.
We will see how well that integrates with the rest.

necessarily in the CPC6512 style, i.e. with 41256-70 (or 44256)

A pair of big SRAM chips sounds more practical, these days.

#4

Technical support - Hardware related / Re: CPC 6128 - white screen, b...

Last post by McArti0 - Yesterday at 19:21

McArti0'd tests before desoldering anything

Let's GO! 

#5

Amstrad CPC hardware / Re: Designing and building the...

Last post by McArti0 - Yesterday at 18:49

necessarily in the CPC6512 style, i.e. with 41256-70 (or 44256)

#6

Programming / Re: Penultimate music player f...

Last post by m_dr_m - Yesterday at 17:30

Oh, Ayane is not yet available (any help welcome).
For now, play in the aaas (Ayane As A Service).

#7

M

Technical support - Hardware related / Re: CPC 6128 - white screen, b...

Last post by mmldrm - Yesterday at 15:30

Have You DM74 or SN74?

SN74 (SN74LS02N).

#8

Technical support - Hardware related / Re: Help with CTM644 Monitor

Last post by Bryce - Yesterday at 13:51

Hi,
    it's highly likely that one or more electrolytic capacitors decided to "retire". I would recommend you (or someone who knows how to if you don't) to replace the those caps. It's quite a bit of work to remove the main PCB, so you may as well replace them all while the board is out.

Bryce.

#9

Amstrad CPC hardware / Re: Designing and building the...

Last post by Bryce - Yesterday at 13:47

some work in this direction has been done in the past. I know I've seen details of a modern KC Compact design using all western 74 Series IC's, complete with a PCB layout. This could save you a lot of the initial groundwork. Maybe someone here knows where it can be found. If not, I can check my archives too.

I am only aware of a modern redesign of the expansion unit that contains the floppy disk controller and the upper 64 KiB of RAM.
If there is a redesign of the system board, too, that could indeed be interesting.

You're right. I was mixing it up with the Aleste 520 project.

Bryce.

#10

M

Technical support - Hardware related / Re: CPC 6128 - white screen, b...

Last post by mmldrm - Yesterday at 13:29

That is what you can get for that price and it is on the low end of usable, however still massively better than a multimeter for digital cirquits. You can actually see what the lines are doing (up, down etc). And exact timing (e.g. fractions of a µs) is not important here.

Also the next better suited would be a proper oscilloscope like the Rigol 1054z (or any other entry level brand and model). But you know, it is even used for 200-300€ .. So I did not recommend it here, but that would be actually my normal recommendation to get into an Oscilloscope.

Nowadays you can get the new Rigol DHO800 series, with the DHO804 the cheapest option. That goes for ~400 Euros. This is a huge upstep with 12bit resolution vs 8bit of the old Rigol and 100Mhz vs. 50Mhz.

Hi. I do appreciate the suggestion of the ZT-702S/ZT-703S. I'm just clueless regarding what level of oscilloscope is sufficient for this kind of work.

So I was a little disheartened to be told that the ZT-702S isn't really up to the job of helping to diagnose the issue here, after buying it for that purpose.

I've requested a return on the ZT-702S. Hopefully that will work out and I can spend the money on a Dandanator instead.

I can also almost hear the shouts of "replace the damn RAM chips" and to be honest it does regularly cross my mind to do this, but I would love for a positive confirmation via McArti0'd tests before desoldering anything.

I hope the above doesn't sound too ungrateful! Thanks again for taking the time to reply here.