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Old 24 October 2015, 21:26   #1
mawrick
 
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A1200 ctrl+Amiga+Amiga reboot won't work (and low sound)

I have a few problems with my A1200,

1 it won't do reset when doing ctrl+Amiga+Amiga, I'v checked that the Amiga keys work by changing between ntsc/pal in the early startup screen - but I can't change between them with the CTRL key - should it ?.

Also when hoovering the mouse over menu bar, and pressing alt+A it will show menus when doing it on the "right hand side keys", but not on the left-hand side - however both Alt and Amiga key on the left side also changes between ntsc and pal, so seem to work......


2. The machine seem to have a very low volume on the sound........


Any tips appreciated.
 
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Old 25 October 2015, 02:46   #2
eXeler0
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I have problems with sound on my A1200 too. I'm thinking it's probably time to re-cap the the motherboard (meaning.. replacing the 22+ years old capacitors)
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Old 25 October 2015, 06:52   #3
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Quote:
Originally Posted by mawrick View Post
I have a few problems with my A1200,

1 it won't do reset when doing ctrl+Amiga+Amiga, I'v checked that the Amiga keys work by changing between ntsc/pal in the early startup screen - but I can't change between them with the CTRL key - should it ?.

Also when hoovering the mouse over menu bar, and pressing alt+A it will show menus when doing it on the "right hand side keys", but not on the left-hand side - however both Alt and Amiga key on the left side also changes between ntsc and pal, so seem to work......


2. The machine seem to have a very low volume on the sound........


Any tips appreciated.
1. It's a keyboard problem. Try to re-seat the ribbon cable inside the A1200, don't pull on it, release the clamp first. If this does not fix it, it could be dirty or just bad. Had same problem on one of my keyboards and the kb membrane was bad.
2. Most likely caps are bad in audio circuit.
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Old 25 October 2015, 11:30   #4
mawrick
 
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Yea, was suspecting the caps in regard to the sound, done some more testing with the keyboard, and turns out if I put an A600 keyboard on it, the CTRL works, but not on the A1200 keyboard.....

Does the CTRL have it's own "line" down the ribbon cable or ? - all other keys seem to be working, how does the ctrl key differs ?.
 
Old 25 October 2015, 13:02   #5
supaduper
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The sound issue can be the chip if the caps have leaked badly, I replaced a couple of these on A600 ,they used the same chip on the A1200 its an LF347 location is U15
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Old 25 October 2015, 14:23   #6
daxb
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KeysPlease from Aminet is nice to check keys. Or just use KeyShow from your Tools drawer to check Ctrl, Shift and Alt keys.
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Old 25 October 2015, 16:19   #7
IanP
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There are seven modifier keys that each have their own circuit on the keyboard MPU they are Ctrl and the left and Right Shifts, Alts and Amiga 'A' keys. If one of these is not working or intermittent it could be, a damaged/dirty switch contact, damaged membrane within keyboard (unlikely), damaged trace on flat flex out of the keyboard, dirty/bad contact at the flat flex connector, a bad solder joint on the flat flex connector, the pull-up resistor pack R621 or the keyboard MPU or a damaged/broken trace on the motherboard.

You can eliminate the keyboard by checking continuity between contact 30 and the contacts for the keys when they are pressed: 6 = Right Shift, 8 = Right Alt, 10 = Right Amiga, 11 = Ctrl, 12 = Left Shift, 13 = Left Alt and 14 = Left Amiga.

Sound problems is likely due to leaked capacitor(s) and leakage can damage motherboard traces and solder pads/joints.
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Old 25 October 2015, 23:13   #8
mawrick
 
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Quote:
Originally Posted by IanP View Post

You can eliminate the keyboard by checking continuity between contact 30 and the contacts for the keys when they are pressed: 6 = Right Shift, 8 = Right Alt, 10 = Right Amiga, 11 = Ctrl, 12 = Left Shift, 13 = Left Alt and 14 = Left Amiga.

does that mena one measuere continuity between pin 30 and 11 on the ribbon cable ?.

how is it numbered ? (if one looks directly at the keyboard as it sits - where is pin 1 (left/right)).
 
Old 26 October 2015, 04:17   #9
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As you look at the keyboard in the normal orientation for typing, with the keyboard tail coming out of the top/far edge, contact 1 is on the left side corresponding to the 1 marked on the motherboard to the left of the keyboard connector and contact 31 is on the right of the tail. Pressing the Ctrl key should make a continuity between contact 11 and contact 30.
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Old 26 October 2015, 11:16   #10
mawrick
 
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Quote:
Originally Posted by IanP View Post
As you look at the keyboard in the normal orientation for typing, with the keyboard tail coming out of the top/far edge, contact 1 is on the left side corresponding to the 1 marked on the motherboard to the left of the keyboard connector and contact 31 is on the right of the tail. Pressing the Ctrl key should make a continuity between contact 11 and contact 30.
alright, thnx for info
 
Old 28 October 2015, 20:28   #11
mawrick
 
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Is there anything one can do to fix the keyboard ? (I'v verified that the ctrl doesn't work (30--> 11 no contact.....), it actually seem to cut of the contact between 12-->30 if both l-shift and ctrl is pushed.....
 
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