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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: sim085 on August 05, 2008, 09:44:36 AM
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Hi,
As I said in the introduction section I just connected my A500+ and everything seems to have worked fine. I have also inserted some floppy-disks and these loaded without any problems. However I found out that the Ctrl + Amiga + Amiga (reset) don’t want to work! Both Amiga buttons work fine when tested independently, but I do not know how I can test if the Ctrl button is working (although I do not see any reason why this button should not work since all the other buttons on the keyboard work fine as well).
Additionally; My A500+ still has the clock battery on it. I already called my cousin so that he can get all the required tools to pull this battery out and then I will try to clean any damaged area. I have found a very good guide how to do this on this forum. However is it possible that the Ctrl + Amiga + Amiga (reset) function was killed because of this? I am not sure about this since the keyboard seems to be on a different board then the motherboard.
Any comments on what the problem could be are more than welcome :)
Regards,
Sim085
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Have you a possibility to try another keyboard? I've got the same problem with one A500 keyboard but Ctrl-A-A works with a spare one. Too bad that this one misses the Backspace key and it needs more than a cap. I wonder if it would help to swap the circuit boards between the keyboards or do I have to dismantle the whole thing to get the backspace button base?
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At the moment I do not have another keyboard to try out however I saw some on sale at eBay. However before buying a new keyboard is it possible to test the Ctrl button on its own? Unfortunately I do not remember the use of this key on the A500+ (apart to restart the computer). If the Ctrl does work fine then could it be something else on the keyboard?
Regards,
Sim085
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If I remember correctly, you have a possibility to test the keys with some of the utils that come with the OS.
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you could test them with that old setkey program (IIRC)
check the plastic beneath the keyboard PCB, the pins might have pierced it and shorted with RF shielding.
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Does this setkey program come with workbench? I think I no longer have any workbench disks :( What is the best workbench version for the A500+ and from where could I buy it? I will buy a hard drive for the A500+ soon so I do not know if that will need a different workbench.
Thanks for all the comments so far :)
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If you have to screen open such as Workbench and Deluxe paint left Amiga + M should switch screen and right Amiga + X,C,V are used cut copy paste, these combinations should work in a text editor.
As for the battery you should be able to use a cell holder from a dead PC. My brother soldered one into our A500+ and the pins line up perfectly with holes in the motherboard.
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Hi Rob,
Unfortunately I do not have any Workbench disk :( However I found the original package of Digita Wordworth. I inserted the Wordworth disk and Amiga Workbench was loaded (some basic form of it at least).
When I press 'Right Alt' + 'Right Amiga' buttons I can see the top menu change and provide options. The same happens when I press the 'Right Alt' + 'Left Amiga'. This means that the Amiga buttons both work.
Also from the top menu I select the option 'Execute Command'. Here when I press any key everything enter fine. When I press 'Ctrl' + 'X' the text already entered is cleared! So I assume the Ctrl also works.
I also tried the 'Shift' button and all other button on the keyboard all seem to work fine.
So at this point I think that the Ctrl and the two Amiga buttons both work. I read somewhere that the problem could be coming from some transistor on the keyboard however not sure if this is relevant for the A500+.
I am happy the all buttons seem to work fine but feel at a loss why the Ctrl + Amiga + Amiga (Reset) is not working :(
I am going to change the battery tomorrow or the day after, maybe I try to put a cell holder from a dead PC as you suggested :) Maybe this is somehow related although I am afraid it is not :(
Is there anyone who is maybe running an A500+ without battery which has the same problem?
Regards,
Sim085
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The battery on a 500+ does nothing more than keep the time while your Miggy is turned off - as far as I know.
So I wouldn't have thought that was the problem.
Dave G 8-)
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If Ctrl-A-A doesn't work there are three possible causes:
- one of the keys is dead (check Ctrl in a shell window: Ctrl-M is , Ctrl-I and so on)
- the line from keyboard to mainboard is dead - check with a multimeter
- the line from the keyboard connector to the rest of the board is dead - check by powering up with disconnected keyboard and short pin 3 to ground; if Amy doesn't reboot, you've found the problem
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Actually, there is a fourth reason.
- a dead transistor on keyboard PCB
There are 2 transistors, one of them is used for reset action. I had this scenario a year ago, solved with equivalent transistor (can remember, BC5xx series for sure)
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Hi Zac67,
Thanks for your reply. The Ctrl seems to be working fine but I will test it again. I will then check the other two points when I open the A500+ to change the battery.
What is the solution for each case? Or the olution is always the same; changing the keyboard?
Regards and Thanks,
Sim085
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No need to change the keyboard.
Look for the 3rd wire (looking on the motherboard connector, left to righ), normally a red one.
It is the reset wire.
Using a wire jumper (with Amiga turn on), short it to the thin shield somewhere. The Amiga must reboot. If so, you have the reset transistor burned (just change it to another equivalent), but first check the wire itself (it may have a bad contact on the connector).
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Actually it's been ages since I've seen an A500+...
Which transistor are you referring to? Q711? That one is only required for power on reset, not for KB reset.
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Checking again the keyboard circuit, the reset line/wire is connected to the pin #8 of the 74LS27 chip on the kb board.
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rkauer wrote:
Checking again the keyboard circuit, the reset line/wire is connected to the pin #8 of the 74LS27 chip on the kb board.
So, stating the obvious here, swapping the chip does the trick?
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Protek wrote:
So, stating the obvious here, swapping the chip does the trick?
If the chip is faulty, yes.
Better check the line with a multimeter first (at dc voltage measurement). When the Ctrl+L-Amiga+R-Amiga is pressed, the chip logic issues a "0" (zero) voltage to that pin.
Simple case of open the Amiga, keep everything in place, turn it on and measure the voltage level on the pin (with and without the key combination pressed). Just be careful to not short the pins on the chip. Better measure the voltage right on the red wire.
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rkauer wrote:
If the chip is faulty, yes.
By ‘chip’ do you mean the ‘transistor’? Sorry for my ignorance but I am not an electronics expert :$ I have also found an image of the A500+ keyboard internals. I found the (red) wire I have to test on this image but cannot identify the transistor. Does anyone have a pointer on where this transistor can be found on the A500+ keyboard?
Regards,
Sim085
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sim085 wrote:
rkauer wrote:
If the chip is faulty, yes.
By ‘chip’ do you mean the ‘transistor’? Sorry for my ignorance but I am not an electronics expert :$ I have also found an image of the A500+ keyboard internals. I found the (red) wire I have to test on this image but cannot identify the transistor. Does anyone have a pointer on where this transistor can be found on the A500+ keyboard?
Regards,
Sim085
The chip contains the transistor. Just look for '74LS27'. :-)
Looking from the picture at Amiga Hardware (http://www.amiga-hardware.com/showhardware.cgi?HARDID=651), it seems that the chips aren't socketed, so soldering is needed. I guess, I'll just swap the whole controller board.
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>Does anyone have a pointer on where this transistor can be found on the A500+ keyboard?
I think you need to narrow it down to that first before you swap transistors or chips. First you should connect pin 3 of the keyboard connector to GND (pin 6 of the same connector is GND or shield as someone suggested and Pin 1 is on the left when you look at the motherboard from the front). If it resets, it's the wire coming from the keyboard or some component on the keyboard. You still don't have to replace the entire keyboard, as you can simply install your own switch to reset using Pins 3 and 6. I had the opposite case happen to me where the reset key was always down (zero volts) so amiga would not boot at all. Simply cutting the wire going to pin 3 made everything work (except the reset). Eventually, the whole keyboard got replaced with a simulated one, but that may not be an option for you.
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Hi again,
Just wanted to thank everyone for all the help given to me so far :) I will reply here with anything new I find regarding the problem!!
Thanks to everyone again.
Regards,
Sim085
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rkauer wrote:
Using a wire jumper (with Amiga turn on), short it to the thin shield somewhere. The Amiga must reboot. If so, you have the reset transistor burned (just change it to another equivalent)
I tested this out the other day and my A500+ did reboot when I short it to the thin shield. Thus means that the reset transistor is burned! Does anyone know from where I can buy an equivalent transistor?
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Hi again,
I opened my amiga today and I do not have any chip marked as '74LS27'. However I have one marked as 'HD74LS27P'. Is this the same chip? Also since this is a chip and not just a transistor is it still easy to find?
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sim085 wrote:
Hi again,
I opened my amiga today and I do not have any chip marked as '74LS27'. However I have one marked as 'HD74LS27P'. Is this the same chip? Also since this is a chip and not just a transistor is it still easy to find?
Yes, HD is the manufacturer "code", 74LS27 is the chip code (a TTL-LS chip) and P means some sort of revision. But prefer to swap the TRANSISTOR before change the (inexpensive) TTL, since it's easier to do.
The transistor (one of those funny black things with 3 legs under it) can be replaced by a BC547 series. Just notice the BC547 have the pins "backwards" compared with the 2SC1815 (C1815 on the transistor itself). The middle pin have the same function. The probable culprit is branded "Q2" on the keyboard board.
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rkauer wrote:
Yes, HD is the manufacturer "code", 74LS27 is the chip code (a TTL-LS chip) and P means some sort of revision. But prefer to swap the TRANSISTOR before change the (inexpensive) TTL, since it's easier to do.
Yes, there seems to be some actual transistors there. Since chips usually have transistors integrated into them, I drew a wrong conclusion, when you talked about the reset line connected to the pin 8 of 74LS27. :oops:
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I think I know for which transistor you mean. So this transistor does not have any specifications? I just ask for a BC547 and they would have even though they where used back in 1991!?
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At least BC547A, 547B, 547C listed in a shop quickly glanced.
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Thanks for your reply. What I meant is if these Transistors are still called with the same name as back then.
I live in Malta and therefore I was hoping I could buy one of these from a local store rather then order them from another country. To buy them I would need to know the name :)
I will try to ask for a 'BC547' transistor. If they don't have then I'll try for the others you mentioned if they are the same type.
ps: found this good article on transistors here:
http://www.4p8.com/eric.brasseur/vtranen.html
:)
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(A500+) Ctrl + Amiga + Amiga does not work.
I think the problem is with your (A500 key.
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weirdami wrote:
(A500+) Ctrl + Amiga + Amiga does not work.
I think the problem is with your (A500 key.
I tried the keys from workbench and individually they all seem to work. I then used a multimeter to check if current is passing properly from the red wire and it is. I then Using a wire jumper (with Amiga turn on), short it to the thin shield and the Amiga reboot. From the other posts they told me that if this happened then it meant that the transistor burned and that I had to change it to another equivalent.
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Hi,
I do not know how this may have happened; However today I connected the joystick today to my computer while it was already switched on. Something happened because the clock (loading) symbol appeared and it did not want to go. I therefore restarted the computer and when I switched it on again the mouse could only move in one direction. I switched it off again left it to cool a little and then switched it on again. The mouse pointer worked fine now, I started playing a game. Just for kicks I pressed the Ctrl + Amiga + Amiga again and it restarted!!! How did this happened? Does someone have any idea? I do not know if the above is realted just wanted to mention what I did today just in case it was relevant.
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Here is an other update ... my keyboard is now acting very strange.
Since the other day Ctrl + Amiga + Amiga worked fine I decided to try it again yesterday and ... It did not work!
However something strange is that the Caps-lock button light flashed green and then off again. When I pressed it it did not want to turn green. I restarted the computer and Caps-lock started working again.
I tried pressing Ctrl + Amiga + Amiga again and again I had the same symptoms mentioned above. However this time I did not switch it off. After a few seconds (maybe half a minute) the Caps-lock flashed again and started working normally.
I therefore tried it for the third time. Again I got the same symptoms after pressing Ctrl + Amiga + Amiga. However this time the whole keyboard did not want to work! Again I switched off the computer; left it off for some time and switched it on again ... everything worked fine again.
It seems that the problems only start after pressing Ctrl + Amiga + Amiga! I still did not change the transistor. However does the above scenario make it clear that the transistor is the problem?
Regards,
Sim085
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I think this has to do with the leaking battery you mentioned in the original post. did you remove it ? was there any leakage ? try to track down if it spilled anywhere and check with schematics if it's interfering with something with the keyboard signals.
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Hi countzero,
Yes I did remove the leaking battery over a week ago. The battery did not seem to have leaked on the motherboard since there was no acid however there seemed to be some (small quantity of) corrosion on the chips near it. I did try to remove this as much as I could although some of it is still there!
However things started acting wierd with the Ctrl + Amiga + Amiga buttons after I connected the joystick when my Amiga was turned on (mentioned this in a previous post). At first these three buttons worked as should (tried them several times) and made the computer restart. Yesterday things changed and started having these weird keyboard moments.
The thing is that I do not have any problems unless I press these buttons!
... Could it be that the when connecting the joystick and speakers the reset transistor got some static electricity which freaked it up more then it already was?