Amiga 500 (or otherwise) keyboard schematics?

chiark

AmiNerd
AmiBayer
Blogger
Joined
Jan 22, 2008
Posts
2,695
Country
United Kingdom
Region
Yorkshire
Hi all
Has anyone got the schematics of an AMiga keyboard which includes the 6570(-036) chip on them?

I have a lovely but broken NMB keyboard, and am trying to repair it. It can't be that difficult... However I've changed the controller (6570) and the timer chip (555) all to no avail!

I can find no shorts on the keyboard matrix.

it's... odd...
 
indeed that is odd.

Have you tried this keyboard on another A500/A500+ ?

worse case scenario - have you tried changing the complete controller board?
 
Therein lies the problem. The whole keyboard is the controller PCB... There is no separate controller board: the upper right hand side of the PCB is the controller...

I've had to repair it for the status LEDs to work as those tracks were destroyed.

I've:
- changed the 555 and 6570 chips
- checked connections and shorts on the HD74LA27P (reset)
- checked connections and shorts on HD74LS123P
- checked for shorts on the 6570.

And to go further I really need the schematics, I think... Or I can try to map them out...
 
does power get to the caps lock LED?
 
Sorry, forgot to mention that bit: yes, power gets to the caps lock LED.

I know this because the caps lock key remains illuminated. It will not turn off. No keypresses work, either.

Reset works, but that's because _RESET is generated by the 74LS24P NOR gates connected in parallel to the keyboard matrix across Ctrl, Amiga and Amiga keys...

Looking at it, there might be a connection problem underneath the lump of hot glue on top of all the connections. There's continuity across all pins, but it doesn't look great... Time to remove the glue.
 
Indeed I`ve had hot glue short stuff out before, mainly a sata HDD that needed cable fastening to it but I got glue on circuit board as well, once power was applied nice majic smoke was seen an HDD never worked again well it did as coasters nice shiney ones :cool:
 
By "continuity across all pins", I mean that Pin 1 of cable connector connects to pin 1 of PCB track ;) , etc... However, after desoldering the cable it seems some were held on with luck rather than anything else so I don't think replacing this will hurt at all...

---------- Post added at 16:25 ---------- Previous post was at 15:59 ----------

Well, that's another potential source of the problem eliminated :(

Any suggestions for test points, anyone?

---------- Post added at 17:37 ---------- Previous post was at 16:25 ----------

Another attempt - changed the 2 transistors (3904s) for ones off another keyboard (labelled C458s).

This causes the Amiga to not even boot when connected.

I'll put the old ones back then :D

(What I'm thinking is that sometime in its past this board has had its connections reversed... but then from the pinout, all that would do is put +5v to the not connected pin, ground the reset, and put kbclk/kbdat on the status leds - and vice versa - so it shouldn't take anything out...)
 
@Chiark: (B)C548, not 458, my friend. Those are very common ( =ordinary) NPN transistors.

Can be replaced by BC338, which are more robust and totally compatible. :)
 
well, they came off another working Amiga keyboard... The older keyboard uses 3904s which are more common: I don't suspect them any more though.
 
Hi guys, I have the exact same problem as the OP:

- After I replaced 2 faulty CIAs with working ones (which fixed all the issues I was having) the keyboard inexplicably stopped working
- Reinstating the faulty CIAs doesn't return the keyboard to working state
- CAPS flashes only once during boot (normal)
- CAPS can be pressed and depressed (lit and unlit) during the boot cycle but once the machine has booted, CAPS stays lit up (if lit when pressed)
- No keys are responsive
- The exception is Ctrl + A + A to reset

What would you try next?
 
Back
Top Bottom