Recapped a 1200, no keyboard

dlsa · Yesterday, 20:03

Hi,

I recapped my amiga 1200. The machine boots off a compact flash HD, I have video, mouse but no keyboard. (I did not connect the floppy but from previous tests I know it tries to boot off from it)
I checked the connector on the mother board with a magnifying len, and it seems ok. I tried two different membranes, but still nothing when I press any key.

What do you suggest I do to try to find the fault that is preventing keys from being registered ? I have electronics tools like multimeters, oscilloscope and such.

Thanks,
Regards

wiz12 · Yesterday, 20:05

Did the keyboard register before you recapped the board?

dlsa · Yesterday, 22:15

yes

wiz12 · Yesterday, 23:48

It could be a faulty keyboard MPU or more likely a broken trace caused by the recapping.

dlsa · Today, 10:13

Indeed I broke a pad while recapping, but I repaired it with a piece of wire. Maybe the job was not done correctly. Itas on the C304 negative pad.
According to the amiga PcB explorer the brokn pad is in the -AV circuit pad.

Elmo Putney · Today, 11:47

That is a de-coupling cap for the +/- 12V for the audio op amp. Unless there was other damage nearby it will only impact the audio not the keyboard.

Mick · Today, 12:17

I'd check continuity around the Keyboard MPU, none of the capacitors are really around anything keyboard related apart from the audio one directly behind the connector. Maybe it was just corrosion and the act of moving the board around to solder has severed something?

Perhaps it could be the voltage detector (U49) that is faulty but it's probably a long shot.

Krashan · Today, 12:49

Check Y621 component, which is a ceramic resonator. It generates 3 MHz clock signal driving the keyboard MPU. Presence of the signal may be checked with an oscilloscope.

Yesterday, 20:03	#1
dlsa Registered User Join Date: Feb 2021 Location: Portugal Posts: 43	Recapped a 1200, no keyboard Hi, I recapped my amiga 1200. The machine boots off a compact flash HD, I have video, mouse but no keyboard. (I did not connect the floppy but from previous tests I know it tries to boot off from it) I checked the connector on the mother board with a magnifying len, and it seems ok. I tried two different membranes, but still nothing when I press any key. What do you suggest I do to try to find the fault that is preventing keys from being registered ? I have electronics tools like multimeters, oscilloscope and such. Thanks, Regards

Today, 12:17	#7
Mick Registered User Join Date: Jan 2004 Location: Yorkshire Posts: 751	I'd check continuity around the Keyboard MPU, none of the capacitors are really around anything keyboard related apart from the audio one directly behind the connector. Maybe it was just corrosion and the act of moving the board around to solder has severed something? Perhaps it could be the voltage detector (U49) that is faulty but it's probably a long shot. Last edited by Mick; Today at 12:28.

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Yesterday, 20:05	#2
wiz12 Registered User Join Date: Feb 2017 Location: Ireland Posts: 771	Did the keyboard register before you recapped the board?

Yesterday, 22:15	#3
dlsa Registered User Join Date: Feb 2021 Location: Portugal Posts: 43	yes

Yesterday, 23:48	#4
wiz12 Registered User Join Date: Feb 2017 Location: Ireland Posts: 771	It could be a faulty keyboard MPU or more likely a broken trace caused by the recapping.

Today, 10:13	#5
dlsa Registered User Join Date: Feb 2021 Location: Portugal Posts: 43	Indeed I broke a pad while recapping, but I repaired it with a piece of wire. Maybe the job was not done correctly. Itas on the C304 negative pad. According to the amiga PcB explorer the brokn pad is in the -AV circuit pad.

Today, 11:47	#6
Elmo Putney Registered User Join Date: May 2022 Location: UK South East Posts: 83	That is a de-coupling cap for the +/- 12V for the audio op amp. Unless there was other damage nearby it will only impact the audio not the keyboard.

Today, 12:49	#8
Krashan Hardware Designer Join Date: Aug 2018 Location: Bialystok/Poland Age: 51 Posts: 184	Check Y621 component, which is a ceramic resonator. It generates 3 MHz clock signal driving the keyboard MPU. Presence of the signal may be checked with an oscilloscope.

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