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AuthorTopic: CDTV keyboard issues  (Read 1801 times)

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Offline hishamk

CDTV keyboard issues
« on: February 13, 2021, 09:38:31 AM »
I have a CDTV with a keyboard that I haven't gotten around to use until now. I found out that the 5 pin DIN connector had a broken pin so I decided to replace it.

I've attempted to replace the connector with a modified ps/2 connector (twisted out the 6th pin and snapped the plastic key bit).

Right now it's a bit of a hacky job with temporary splice connectors to see if it works. I've done the following connections (see attached diagram):

C12 connector on keyboard circuit:
RED - GROUND
WHITE - DATA
YELLOW - CLOCK
ORANGE - +5v
Case Ground -> Connector Shield Ground

So on power up, the keyboard's caps lock key blinks once as usual. However, once it gets to AmigaDOS a constant stream of apostrophes is typed (raw code 00) (no, that key is not stuck - even if it was, I would still be able to type other characters). Pressing keys on the keyboard does not do anything, including the reset combo. Pressing caps lock works (light on/off) but then after five presses or so it stop to light up. The '`' stream continues indefinitely nevertheless.

To test whether the keyboard actually works and that the MCU is not fried, I tested it with my A3000 (I just swapped in the cable from the A3000's keyboard). It worked fine on the A3000.

I also decided to try the A3000's keyboard on the CDTV with my hack cable and the result was the same as with the CDTV keyboard, a series of never ending '`', and no other keys responding, including reset combo.

So this tells me the keyboard is fine. It's something else that's gone amiss.

I swapped around the CDTV's odd and even CIAs and that didn't make a difference.

So I'm beginning to guess that either my hacky connection is wonky or that it's something between the keyboard port and the CIAs that's causing an issue.

Would it be worth replacing both CIAs with completely new ones? I've got a few donor machines I could pull those out from. FWIW I've tested the CIAs with Amiga Test Kit and everything passes.

Does anyone have any suggestions on what could be wrong?


Thanks
« Last Edit: February 13, 2021, 09:53:17 AM by hishamk »
2x A1000, 2x A2000, 1x A3000, 2x A1200, 2x A500, 1x CDTV, 1x CD32, 2x Pegasos II, 1x EFIKA
 

Offline Pat the Cat

Re: CDTV keyboard issues
« Reply #1 on: February 13, 2021, 08:27:37 PM »
... You might have CLOCK and DAT mixed up on the hacked cable? Or the pins are shorted on the hack cable?

"To recurse is human. To iterate, divine."

A1200, Vanilla, Surf Squirrel, SD Card, KS 3.0/3.z, PCMCIA dev
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Offline hishamk

Re: CDTV keyboard issues
« Reply #2 on: February 13, 2021, 09:48:55 PM »
I did try them swapped, but then there’s nothing at all, not even the apostrophe.

Tested both ends of cable for shorts and continuity and it all checks out.

2x A1000, 2x A2000, 1x A3000, 2x A1200, 2x A500, 1x CDTV, 1x CD32, 2x Pegasos II, 1x EFIKA
 

Offline Pat the Cat

Re: CDTV keyboard issues
« Reply #3 on: February 13, 2021, 10:36:15 PM »
No response at all with them swapped?

Well, you got the power and gnd correct, otherwise the LED wouldn't come on.

Apostrophe = raw keycode 000000000. Looks like something is grounding the keyboard data...

Maybe if you had the power connectors wrong, but the CN7 connector (which takes the signal to the motherboard) is upside down? That would ground out the data line but leave the clock intact.

https://ia801904.us.archive.org/2/items/CDTV_Service_Manual_1991-05_Commodore/CDTV_Service_Manual_1991-05_Commodore.pdf

On CDTV, the kdata and kclock go to the 6500 chip first (from CN7) and then somehow get routed to the even 8520 CIA.

Proceed with caution, always make certain the +5V and GND are connected right before powering on.
"To recurse is human. To iterate, divine."

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Offline Pat the Cat

Re: CDTV keyboard issues
« Reply #4 on: February 13, 2021, 11:09:46 PM »
One other point - if you have a CDTV remote, turn it off when testing. (I forgot why the CDTV has an internal keyboard controller like the 6500).

I really do think it's a bad connection rather than faulty chip. Or maybe a cap has leaked and shorted KDAT to ground or similar? 

EDIT: Five pins needed on a CDTV? Keyboard detect sense pin? You could try grounding that.

http://www.rockus.at/Amiga/cdtv2a4000.html

https://aminet.net/search?query=cdtv+keyboard
« Last Edit: February 14, 2021, 01:19:11 AM by Pat the Cat »
"To recurse is human. To iterate, divine."

A1200, Vanilla, Surf Squirrel, SD Card, KS 3.0/3.z, PCMCIA dev
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The following users thanked this post: hishamk

Offline hishamk

Re: CDTV keyboard issues
« Reply #5 on: February 14, 2021, 01:03:54 PM »
Thanks @Pat the Cat for the help so far.

I just tried it with the keyboard sense grounded but it's still the same infinite apostrophes.

« Last Edit: February 14, 2021, 01:06:04 PM by hishamk »
2x A1000, 2x A2000, 1x A3000, 2x A1200, 2x A500, 1x CDTV, 1x CD32, 2x Pegasos II, 1x EFIKA
 

Offline Pat the Cat

Re: CDTV keyboard issues
« Reply #6 on: February 15, 2021, 02:17:42 AM »
No detail included on the iff on aminet I linked to?

I was half thinking you had the dat and clk swapped again.

Apart from that I'm out of ideas on this one.
"To recurse is human. To iterate, divine."

A1200, Vanilla, Surf Squirrel, SD Card, KS 3.0/3.z, PCMCIA dev
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Offline hishamk

Re: CDTV keyboard issues
« Reply #7 on: February 15, 2021, 03:14:47 PM »
No, it was pretty much what I had.

I've also checked continuity across the port, keyboard SSM and CIA and both data and clock pins seem to be fine.

My issue seems very close to this one: http://eab.abime.net/showthread.php?t=94188 - he even got the apostrophes :)

He seems to have resolved it with a beefier PSU.

2x A1000, 2x A2000, 1x A3000, 2x A1200, 2x A500, 1x CDTV, 1x CD32, 2x Pegasos II, 1x EFIKA
 

Offline hishamk

Re: CDTV keyboard issues
« Reply #8 on: February 17, 2021, 07:11:55 PM »
I measured the voltage going through the keyboard and it's at 4.65v. Not sure if this is off 5v enough to cause issues though.
2x A1000, 2x A2000, 1x A3000, 2x A1200, 2x A500, 1x CDTV, 1x CD32, 2x Pegasos II, 1x EFIKA
 

Offline Pat the Cat

Re: CDTV keyboard issues
« Reply #9 on: February 17, 2021, 08:01:28 PM »
It could be. One way to test would be thicker cables - perhaps if you have a spare 5 pin connector for the A3000 keyboard, you could rig up wires going straight into the port?

4.65 is very low, is the board on the CDTV that low too? It's not going to help.

I think tolerance limit is 5%, which would be 4.75. Just a touch higher and it might just work. Hence the thicker cables.

Mind you, if you've got less than 4.75 on the board (coming from the power supply) that's not going to help either.

Cable length is a factor too, if you've got a very long keyboard lead, the voltage will drop more than a short one.

A recap on the power suplly might well sort it. Try fix rather than replace.
"To recurse is human. To iterate, divine."

A1200, Vanilla, Surf Squirrel, SD Card, KS 3.0/3.z, PCMCIA dev
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Offline Pat the Cat

Re: CDTV keyboard issues
« Reply #10 on: February 17, 2021, 10:17:31 PM »
 Hold it - just sticking a thicker piece of wire in between the pin and the current wires isn't going to make a difference.

Measure the voltage on the board. If it's at 5V, then fitting thicker wires to completely replace the present one will make a difference.

I suspect you'll find it's about 4.8V, marginal for operation. IE you were correct, it's the power supply, not you using thinner wires on the connection.
"To recurse is human. To iterate, divine."

A1200, Vanilla, Surf Squirrel, SD Card, KS 3.0/3.z, PCMCIA dev
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Offline hishamk

Re: CDTV keyboard issues
« Reply #11 on: February 19, 2021, 11:00:32 AM »
Well, I measured the voltage between the port Vcc/GND pins and it's 4.99v. I've also linked the keyboard with a much shorter cable and the voltage is at 4.99v on the keyboard's mobo.

I've measured continuity across the port, 252609-02 chip, and CIA. Data and clock lines are fine.

I switched the CIAs, swapped in a different Gary and it's still the same. The apostrophes persist. All tests done with an extremely short connection at 4.99v.

The only thing left is to swap in a new 252609-02.

Not sure if there are any other things I could check. I have an old oscilloscope that I could pull out and peek at signals, but need some help as to what exactly to look for.


« Last Edit: February 19, 2021, 11:43:19 AM by hishamk »
2x A1000, 2x A2000, 1x A3000, 2x A1200, 2x A500, 1x CDTV, 1x CD32, 2x Pegasos II, 1x EFIKA
 

Offline Pat the Cat

Re: CDTV keyboard issues
« Reply #12 on: February 19, 2021, 07:18:14 PM »
Check the DATA line on the keyboard. Hook up the scope with clips if you can, see if pressing a key gives you all lows or all highs no matter what key you press.

I'm guessing it would be all highs. Which would point to the DATA line being held high by something inside the CDTV as you figured already.

Especially if it's happening between the two keyboards, which work fine otherwise.

There is also a crystal oscillaor in the keyboard, you could check that to make sure the keyboard controller is getting a nice clean regular signal (unlikely to be that, but worth checking,

Now, assuming all the above is correct... to be positive it is the CDTV - repeat the test with the DATA line disconnected from the CDTV, but the clock and power lines connected.

You should see the data line wiggling up and down freely if it really is the CDTV. When different keys are pressed or released.

Finally, check with no power at all on the port. Is the data line shorted to the +5V line? Or does it float around?

If it floats, it's got to be a faulty component. If it's short, then it's a short on the board somewhere rather than a faulty component (harder to find, easier to fix than getting a spare chip).

It could just be a faulty resistor pack inside the CDTV,.. Might not be such a difficult replacement,

To verify that, again with the power off, check continuity between pin 39 on the even CIA and the DATA pin on the connector. then continuity between the CIA chip and the +5V rail.

Both the KClock on pin 40 and DATA on pin 39 of the even CIA are connected to a pull up resistor pack. If that's gone from being a 10K resistor to being close to a dead short (as far as the DATA pin goes) that would cause the fault.

EDIT: Resistor pack is labelled RP6 on the schematic.

EDIT EDIT: When you get to measuring resistance between KDATA pin 39 of the CIA and +5V (should be no lower than 9K Ohms allowing for tolerances) then do take the chip out of the socket. That way no circuits in the chip will interfere with the measurement.

If it is much lower, replacing the resistor pack should fix it. You might have trouble finding one with the right number of connections though.
« Last Edit: February 19, 2021, 08:51:05 PM by Pat the Cat »
"To recurse is human. To iterate, divine."

A1200, Vanilla, Surf Squirrel, SD Card, KS 3.0/3.z, PCMCIA dev
A500, Vanilla, A570, Rev 5, KS 1.2/1.3 Testbench system
Rasp Pi, UAE4ARM, 3D laser scanner, experimental, hoping for AmigaOS4Arm, based on Watterott Fabscan Pi
 

Offline hishamk

Re: CDTV keyboard issues
« Reply #13 on: February 26, 2021, 07:50:49 AM »
It looks like it's RP6. The resistance is pretty shot for 40 and 39 against +5V. It's around 2 ohm.

I didn't do the oscope check since I was concerned about grounding (I have an old Tektronix analog scope and the CDTV appears to be earth grounded - not an expert on these things though).

I have individual 10k ohm resistors. I was wondering if there's a way to hack them temporarily on to the connections to see if that'll fix things before replacing RP6 outright. Possible?

In any case, I've sourced a 10-ohm 10-pin pack but it might take a week or so to get here.

Cheers
« Last Edit: February 28, 2021, 10:32:59 AM by hishamk »
2x A1000, 2x A2000, 1x A3000, 2x A1200, 2x A500, 1x CDTV, 1x CD32, 2x Pegasos II, 1x EFIKA
 

Offline Pat the Cat

Re: CDTV keyboard issues
« Reply #14 on: February 26, 2021, 08:01:24 AM »

I have individual 10k ohm resistors. I was wondering if there's a way to hack them temporarily on to the connections to see if that'll fix things before replacing RP6 outright. Possible?


Hmmm... would mean soldering to the pins of the chip. (2 pull up resistors, one for kclock, one for kdat).

If you had a IC socket to solder to, and plug the even CIA on top, then yes. I'd be wary about soldering direct to a CIA chip, they seem a bit fragile (very prone to static shock).

I've seen somebody blow up a CIA chip just doing a continuity test on a live Amiga (GadgetUK164). All he was doing was measuring voltage to the serial port.

If you have a socket, it's worth doing just to make sure it really does fix the keyboard problem.

Changing a resistor pack means dismounting the whole board, worth looking for any other faults first (battery? etc etc etc).
"To recurse is human. To iterate, divine."

A1200, Vanilla, Surf Squirrel, SD Card, KS 3.0/3.z, PCMCIA dev
A500, Vanilla, A570, Rev 5, KS 1.2/1.3 Testbench system
Rasp Pi, UAE4ARM, 3D laser scanner, experimental, hoping for AmigaOS4Arm, based on Watterott Fabscan Pi