strange keyboard failure...

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Last seen: 4 years 7 months ago
Joined: Mar 20 2014 - 15:43
Posts: 75
strange keyboard failure...

strange keyboard failure on several board / keyboards....

I have:
3 Apple IIe boards NTSC
1 Apple IIe board PAL

all these boards were working recently

I have
1 usb to apple IIe keyboard converter
1 standard Apple IIe keyboard
1 Apple IIe platninium keyboard (looks like new)

all these keyboards / board worked

now with all the board (mixed with all keyboards) I have the same symptome..

no way to type on the keyboard (except ctrl/apple/reset)
and the cursor is moving from left to right as if I was typing on the 'space' key all the time

I have 3 different keyboard (same symptomes with all cables)

if it was on apple II standard I would think the strobe is stuck

any idea of the source of this problem ?


PS: the test was done without any cards in the slots...
so the problem is not due to a bad board

speedyG's picture
Last seen: 5 years 4 weeks ago
Joined: Nov 16 2011 - 07:45
Posts: 2493
Re: strange keyboard failure...

Hello dvador,

it looks like the USB to //e converter has either killed the internal keyboardchip
or it is wrong. Maybe thereafter it killed the keyboardchips on the mainboards.
suspects at Mainboards: at least the AY5-3600 gets permanent Strobe signals...
100kOhm R27 at ENKBD or
damaged 100kKohm R32 or
damaged 47pf capacitor C70.
P.S. somebody posted in former posting doubt that the adapter was not wired correct...

Last seen: 4 years 7 months ago
Joined: Mar 20 2014 - 15:43
Posts: 75
Re: strange keyboard failure...

in fact no, later it worked again... on all boards / all keyboards...

I guess it's a problem of interference with something... but I still dont known what

this adapter is badly programmed...
in the code i found a lookup loop that was very long
just by keeping a key at the bottom of the map pressed
it crashed the usb and we got a reboot
(occured from time to time with a qwerty keyboard, and frequently with azerty)

I'm using a modified version of the code
where the usb scancode is used as a direct index into a table
so the access to the data is really fast and I have no more usb resets...

I gave my modification to the author but he never used it

I'm making adapter for commodore, I'll make one for the IIe

thanks for these information, I'll check these location when it will happen again
perhaps that the capaciter is permanently charged / discharged when it should not...
I'll check the schematics and I'll take the oscilioscope to investigate

Last seen: 4 years 7 months ago
Joined: Mar 20 2014 - 15:43
Posts: 75
Re: strange keyboard failure...

btw are you speaking of:

this adapter ?
or this one ?

mine is the previous version of this one:

my version can be installed in the slot but there are non connection on the connector but copper everywhere on the connector
so if the solder mask is attacked but the metal of the connector you can create a giant short circuit...

which one has problem ?
is there another one ?


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