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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: BGary335 on October 13, 2006, 11:32:10 PM
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I recently purchased an A500 off of EBay. Upon powering it up, I get no lights other than the Caps Lock key, which stays lit continuously, and no video (I'm using an A520 adapter, by the way). However, I can tell a video signal is going to the TV when I switch the computer on, there's just nothing on the screen. I try inserting a floppy, and get nothing from the computer, except a momentary spin of the floppy drive. I tried replacing both the Agnus chip and the Kickstart ROM (in fact, I've tried several of each)but nothing changes. I've noticed that neither the CPU chip nor the Kickstart ROM get even a little warm. The rest of the chips however seem to heat up at least a little.
Any ideas on what the problem might be? I'm thinking maybe its the CPU, butI'm not sure. Any help wouldbe very much appreciated!
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Any ideas at all?
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tried another psu?
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A firm push to every socketed chip - or remove and reseat, that's the first thing to do.
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zipper wrote:
A firm push to every socketed chip - or remove and reseat, that's the first thing to do.
Also, connectors can get a bit rusty, so try to make it clean (I always use a tip of a towel wich is a very tiny bit wet). And also make sure you give the floppy cable a push too.
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Yes I have tried another PSU, and it made no difference.
Yes I ahve inspected all the chips and connectors, cleaned them, and made sure they were seated properly.
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Un-lock the CapsLock key, and report back. Everything reverts back to an Agnus problem, but you need to un-lock that key first to know anything else.
Is the 68000 hot?
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@ Amiga4k
I'm sure he means that when he switches on the caps lock light comes on and stays solid. He isn't pushing the caps lock key.
From memory this is a fault indicator on Amigas, but I have no idea what it means.
I seem to recall it was something to do with the CIA chips but I don't really know. Anyone?
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@ ajlwalker:
You are correct. I am not pressing it, rather when I switch the system on, it comes on and stays on for about 5 minutes, then goes off. Just seems to me to be longer than it should be. Granted, I haven't used a 500 in 5 or 6 years, but from whatI can remember the Caps Lock light never stayed on that long on boot up.
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Well the problem seems to have worsened. All I get when I power up now is a continuous Cpas lock light and nothing else.
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Did you try swapping the CIA chips and see if it works then?
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Try booting up with the keyboard disconnected - it could be a faulty chip on the keyboard. Can't remember off hand what it's called, but you'll find it adjacent to the LED's. Usually a faulty keyboard chip will generate a flashing sequence through the caps lock LED and prevents the Amiga from booting up. This kind of problem seemed to affect A500+'s more than A500's. From what I remember, the chip is soldered directly to an A500+ KB and socketed on an A500.
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Did you talk to the sellar about this ?
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@Argus
What are the CIA chips? Sorry but I'm not too familiar with anything other than the Kickstart ROM chip, the CPU, and the Agnus.
@HellCoder
Yes but it was sold as is, and all he'll give me is the same one-liner:Sorry it was sold as is. Not even an attempt at helping. It's that attitude that leads me to believe he was just trying to rip someone off. Yes, the auction did say as-is, but when you give a real nice description of the computer, and include none of the bad stuff, its hard to not buy it. If he would've given some reason for why it was being sold as is (like maybe that it doesn't power up), than I wouldn't have bought it. Unfortunatately, I had to make a decision based on what info he did give, and as you can tell I made the wrong decision.
@DrDekker
I've tried disconnecting the keyboard, but it doesn't seem to have made any difference.
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What are the CIA chips? Sorry but I'm not too familiar with anything other than the Kickstart ROM chip, the CPU, and the Agnus.
They are the 2 chips on the mainboard marked "EVEN CIA" and "ODD CIA". They are quite often the cause of numerous problems.
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I have not swapped those. Right now I don't have any other CIA chips to swap them with.
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BGary335 wrote:
I have not swapped those. Right now I don't have any other CIA chips to swap them with.
BGary, just try swapping one with the other (they're both the same), and see if there's any difference at all. That way you'll at least know whether or not you're on the right track.
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Ok, did that, and here's where we're at now: When I switch the system on, the Caps Lock light and now the floppy light both come on and stay on continuously. Now I'm even more confused. Why has the floppy light decided to come on? Are we going in the right direction?
Oh, also, there is no video. The screen flashes when I power the system as if its about to send video to the TV but nothing happens.
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Sounds like we're definitely on the right track. If both CIA's were functioning, there wouldn't be any change (unless they happened to be seated improperly, but you checked that).
You can buy these from Softhut. (http://www.softhut.com/cgi-bin/test/Web_store/web_store.cgi?page=catalog/hardware/custom_chips/chip_cia.html&cart_id=4289450_35348) If you're lucky, you might find a complete 500 at a local thrift store (Salvation Army can be a good spot) for even less.
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When you turn on your Amiga, it has a rather long and complicated set of routines through which it must go before it can allow you to interrupt it. As the startup process goes along, Amiga is trying to let you know whether all is well. There has been a small problem with this, however - Commodore forgot to tell us what the signals mean!
Here is a list of the startup-routine activities:
1. Clear all of the chips of old data.
2. Disable DMA and interrupts during the test.
3. Clear the screen.
4. Check the Hardware (make sure the 68000 is working)
5. Change the screen color to show whether this test was passed
6. Do a checksum test on all the ROMS
7. Change screen color to show if ROMS passed the test
8. Begin the system startup
9. Check the Ram at $C0000, and move SYS_BASE there
10. Test all of the chip RAM
11. Change the screen color to show if the RAM passed the test
12. Check to see if software is coming in OK
13. Change the screen color to show if the software test is
passed.
14. Set up the chip ram to receive data.
15. Link the libraries.
16. Check for additional memory and link it in if found
17. Turn the DMA and Interrupts back on.
18. Start a default task.
19. Check to see if the computer is using a 68010, 68020, and/or
68881.
20. Check to see if there is an Exception (processor error)
21 If so, do a system reset.
AND THE MESSAGES ARE IN TECHNICOLOR!
As this routine is taking place, the Amiga is sending you
messages with the screen colors. If all is well, we usually see
this sequence:
Dark gray The initial hardware tested OK. The 68000 is running and the registers are readable
Light gray The software is coming in and seems OK
White The initialization tests were all passed
But if something is wrong with your Amiga, you might see:
Red If there is an error in ROM
Green If there is an error in the Chip RAM
Blue If an error was found in the custom chips
Yellow If the 68000 found an error before the error
trapping software (the guru) was up and running
The most likely of these errors seems to be the error in Chip RAM. Only this week, I saw an AMIGA 500 flash a brilliant green screen when an expansion RAM board was put in hastily, and did not settle in correctly. A positioning of the board corrected the problem in that case. I have not yet seen a red, blue, or yellow screen indicator.
KEYBOARD MESSAGES
The Amiga keyboard is not as dull an object as I had originally thought, either. It contains a processor of its own - a Rockewell/NCR/MOS Technology 6500/1. It also has 2K of ROM, 64 bytes of RAM, and four I/O ports of eight bits each. There is a built-in crystal oscillator running at 3Mh, also. All but the very earliest of keyboards also have a "watchdog timer" which will reset the keyboard's processor if it stops scanning the
keyboard for more than 50 milliseconds.
It is possible for the computer to be powered up before the
keyboard is plugged in, in which case the keyboard will have to go through its self-test after it is connected to the computer.
Most of us, however, will have the keyboard attached, and the self-test will take place while we are watching the screen, changing disks, etc.
The keyboard self-test consists of four steps. First it does a checksum on all of the ROMs. Then it checks the 64 bytes of RAM, and then the timer is tested. Then the keyboard must achieve proper synchronization with the computer. It does this by slowly clocking out 1 bits until it receives a handshake pulse from the computer. Once this pulse is received, the keyboard must inform
the computer of the results of its self-test. Should the self-test fail, the code for failure can be sent to the computer without waiting for the handshake pulse.
IN CASE OF FAILURE
After informing the computer that the self-test has failed, the keyboard will then try to notify the user that it is in trouble.
This is done by blinking the CAPS-LOCK light. Here is the code:
One blink The keyboard ROM check failed
Two blinks The keyboard RAM check failed
Three blinks The watchdog timer test failed
Four blinks A short exists between two row lines or one of the seven special control keys
The last check had not been implemented at the time my Rom Kernal Manual was printed, but was in the plans. It would be unusual for the user to have typed anything during this self-check time, but if any keys have been depressed, the codes for those keys would then be sent to the computer, a "terminate key stream" code would be sent, and then the CAPS LOCK LED shut off, indicating the end of the keyboard startup sequence.
Should you be so unfortunate as to have your Amiga get into
difficulties, perhaps these codes will help you and your repair man to put it in good health again.
(The information on startup routines came from messages on Usenet, and the keyboard information from the Amiga Hardware Manual.)
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@Erol
Those codes aren't much help at all actually at this point in time because there is no video of any kind whatsoever. Beleive me, if I was getting any color screen, I wouldn't leave that information out! Also, the Caps Lock light does no kind of blinking at all. It is solid from the time I turn the system on until the time I turn it off.
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Found some links that might be of some help:
Startup error diagnostics (http://main.aminet.net/hard/misc/errormessages.txt)
Schematics and service manuals, "tech topics"
[url=http://theweeks.org/toms-stuff/AMYHACKPAGE.html#TDTTT] Links page, may be some useful info here (http://www.shiftreload.com.au/users/4x4/schematics/index.html)
And I hate to ask the obvious, but have you taken a very close, thorough look at the board, to check for anything that looks like it may have gotten hot? Or maybe a previous repair/upgrade gone wrong... (f.e, A500 motherboards required different modifications when upgrading to the 1 MB Agnus (popular), maybe a bad solder joint or someting around JP2? I had one of these once... drove me nuts!)
Regards,
Damion
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Try swapping the CIA chips round, temporary test until you get replacement chips.
To swap the CIA chips you will need to take the Amigas case off and remove the metal shielding underneath. The two CIA's are both 40-pin chips that are marked CIA ODD and CIA EVEN. Simply swap them over, making sure that you have placed them in the right way and replace the case.
Temporary solution till you get a replacement chips.
If it was a RAM or Agnus problem your video screen would go green.
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@Erol
We've already done that. See the previous page of this thread for the result.
As for looking voer the board, yes I've done that and haven't found anything that looks wrong.
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It sucks that you don't have a video signal. Do you only have that A520 modulator at your disposal or do you have other ways to connect it to a monitor/tv?
If your modulator doesn't work, you can keep changing chips until god knows when, but it wouldn't help...
Just asking.... :)
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In addition to the modulator, I have also tried the monochrome video out, but I get the same result. Other than that, Ihave no other way of hooking itup to a monitor or TV.
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go to ebay, type in this item number
140042120376
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Might seem a stupid question but - you have tuned your TV in to receive the signal haven't you?
The frequency should be similar (if not exactly the same) to the output from a VCR.
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I appreciate everyone's help, however I've given up on it. It's probably nothing that can be fixed. I'm going to sell it on Ebay for parts. I have, however, just received another 500 which, thankfully, seems to work just fine! I do have one question for you guys though: It currently has a Kickstart 1.3 ROM, and I have a 2.0 ROM I'd like to upgrade to-how much work is there to it? Does it involve soldering? Thanks agin for your helpy guys, I really appreciate it!
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There's no soldering required at all.
1 - open the case
2 - make sure you are not loaded with static electricity
3 - carefully remove the 1.3 ROM (I always use a screwdriver, but be careful - never use more force than needed)
4 - enter the 2.0 ROM in exactly the same way
5 - push it down firmly but carefully
6 - close the case
7 - enjoy :-)
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Great! For some reason I was under the impression that there was a jumper line on the board that had to be soldered.
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Depends on your mobo revision - rev.6 or higher needs no alterations.
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How do you tell what version it is? Is it written on the board somewhere?
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Yes.
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I still have not seen any replies about if you checked the psu or not?? And also try disconnecting the floppy drive. If something is wrong with it, or if cable is connected wrong way, then the drive light would be lit all the time and that could also stop the computer from booting.
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Stay with 1.3!
It is compatible with most software. I have so many 2.04+ OSs that it was hard to find a 1.3 machine.
STAY WITH 1.3 on the 500!
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Tomas, I have replied. Look again.
@sdyates,
I have more software for 2.4 than 1.3 so upgrading to 2.0 would be the best way for me to go I think.
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Hi, BGary335
If you really can`t get it going (and I`ve read all the posts and can`t think of the problem) let me know what board revision you have and I will send you a MoBo from one of the many I have for nothing apart from postage costs.
I`m in Dorset in England so you can calculate postage from where ever you are.
Regards, Amigaman61
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I've sent you a Private Message.
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Have you received my PM?
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http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=110045459700
anyone seen these on ebay, the seller has loads listed.
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I've actually seen quite a few of those on Ebay.
BTW, what does this have to do with this topic? :-D
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BGary335 wrote:
BTW, what does this have to do with this topic? :-D
Open forum discussion, A500 topic.. just though someone would be interested rather than posting a new post again. ;)
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Actually its called hijacking when you come into a thread and post something that has nothing to do with the topic at hand. :roll:
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@BGary335 -
:lol:
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That's called ignorance. :roll:
Or have you really never heard the term hijacking?
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BGary335 wrote:That's called ignorance. :roll:
Or have you really never heard the term hijacking?
Actually it is called, "Threadjacking".
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The two terms are actually interchangeable. I've seen both used on many occasions.