Keyboard problem

[itexas]

I have one schneider cpc 464 and got this pictures on display. Any idea how to solve this? When i type, thers always one "space" btw word and thers slightly delay in typing.

[Devilmarkus]

Looks like a problem in the CRTC chip...
Also the delay is often caused, when a CRTC register is badly set.

You should try to check this chip and, perhaps, swap it...

It's the HD46505SP (Hitachi) on this board rev: http://cpcwiki.eu/imgs/9/91/CPC464_PCB_Top_%28Z70100%29_GA40007-4.jpg

Could also be a MC6845P (Motorola)

[itexas]

ty, i will try to do this

[ralferoo]

It looks like when MA0 from the CRTC (which maps to address line A1) is 1, then the RAM returns 00 bytes. MA0 is pin 4 on the 6845.

However, MA0 is only directly connected to one chip, one of the 74LS153 on pin 3. It's labelled IC105 on my 6128 schematic, and don't have a 464 schematic to hand at the moment. If there was a short from pin 3 (MA0) to pin 2 (NCPU) or 4 (CCLK) on the 74LS153, they might cause this kind of problem.

So, try to test the resistance between these pins on all the 74LS153s. If you find one with a short between pin 3 and either 2 or 4, I think it's probably your guy.

It's possible the trace from pin 4 of the 6845 to pin 3 on the 74153 also has a short to something else too, so try to follow it too.

[itexas]

gonna check that2, ty for answer

[MacDeath]

You're from Serbia ?
Must be quite difficult to find such Amstrads there, perhaps from Greece...

[TFM]

Could be a problem in the ROM, causing problems with the print routine. Can you check the ROM content for integrity?