Problems my new old A500

07 March 2004, 18:39

Hi, I recently bought a refurbished A500 from a guy on eBay. I've lurked a bit on this board in the hopes of finding a solution my problem but so far I haven't had much luck.

Ok so I'll try and give as complete a story as possible... Bought the Amiga from the US and got a faulty european power supply. One email later I get a replacement which seems to work. I also fitted a 512k Technoplus Amiram module. This didn't fit so well and on closer inspection had what I think is a broken capacitor on it. On first power up with this poorly fitted ram and the new PSU I got a somewhat corrupted looking "insert disk" image on the screen. After I inserted Workbench 1.3 I briefly saw what I guess was a workbench startup screen with mouse pointer. This then changed to a green screen and stayed that way. Each subsequent power up resulted in just the green screen which I understand can mean a problem with the chip ram or with Agnus.

This is where things go nasty. I decided to open up the Amiga and I very carefully removed and reseated the Agnus chip as well as a few others. I also ditched the nasty RAM board. Power up now results in a black screen. I have no real idea what has happened at this point. I know that most of the chips are warm when the Amiga has been powered up with the exceptions of Gary, Kickstart and the chip RAM.

Phew. Sorry, I realise that the above is something of an epic. I'm hoping someone can help me out so I can become a productive member of the Amiga community

Amiga1992 · 07 March 2004, 19:22

Dumb check but, have you reseated the chips in its correct position? Hope you did.

And why did you connect the RAM board if a capacitor was blown? That surely hurted the Amiga somehow. The moment the gfx were corrupted you should have removed that thing

Let's wait for overdoc to come and give more hints (hey he's Dr. Commodore

)

07 March 2004, 19:42

Quote:

Originally posted by Akira
Dumb check but, have you reseated the chips in its correct position? Hope you did.

And why did you connect the RAM board if a capacitor was blown? That surely hurted the Amiga somehow. The moment the gfx were corrupted you should have removed that thing

Let's wait for overdoc to come and give more hints (hey he's Dr. Commodore )

Not such a dumb check- but I they're all correct afaik. The RAM board was fitted before I noticed the damage, a small chip out of the side of the capacitor. It was sold to me as being in perfect condition, I had a little too much faith

Overdoc · 10 March 2004, 11:28

Well, black screen can happen from almost any part in the computer if it is damaged too far !

But from your description the problem seems to have been cause by the ram board.
So, this means Agnus, RAM chips or some of the other memory associated chips ( like the 74LS244 ) might have problems.

I would say first check if you reseated every chip correctly ? Are all chips inserted in the right direction ? Is the Agnus socket still ok ? ( it can easily break when the Agnus is removed ! ). Also, is the diagonal edge on the Agnus facing the diagonal edge on the Agnus socket ? Remember that the print on the Agnus chip most of the times is facing to the left or right, sometimes also upside down if I remember correctly, so it doesn't mean anything for the correct fit of the Agnus !

Hard to say what exactly might be damaged or if it is just a bad contact problem, but the distorted startup screen definitely point to a Agnus problem ! I have had similar problems with an Agnus chip once ! ( one pin had bad contact to socket and contact with another pin )

Also, check if you might have bent some pin on the edge of the Agnus ?

Sorry, that's all hints I can give you right now....

10 March 2004, 12:31

I'll have a good look when I get home and let you know how I get on! Thanks Overdoc!

14 March 2004, 17:59

Well, no joy I'm afraid. I must have done some serious damage. Fat Agnus is correctly seated and the socket appears fine too. It this rate I'd be happy to get back to a green screen. At least I know what that means...

Any further suggestions or is it time to just buy a new A500?

14 March 2004, 18:02

I just read another post about RGB>Scart leads. I'm using one of those but was also was using it when I got the disk screen and the green screen... So unlikely to be a factor but thought I should mention it.

Overdoc · 15 March 2004, 12:48

Hmm, have you done the heat check, yet ?
If the problem has to do with the Ramcard, then it must be someting which has to do with Ram, Agnus or one of the TTL chips connected to ram. Also the green screen points to this.

Just Leave it on for a while and feel if any of the Rams or any of the 4 (?) TTLs get hot ?

15 March 2004, 14:12

This is something I did check quite early on- whilst Agnus does get warm, it's no warmer than any of the other chips... My board is one of the earlier revisions so I have 16 ram chips. These all remain cool, they don't seem to warm up at all. Not really sure what that means! I'm not sure I know what the TTLs are, so I will figure out where they are and check them next.

There is something else which may or may not be significant. Both of the LEDs on my keyboard remain lit constantly on power up. The caps lock LED remains dark though.

[EDIT] I have checked the chips again and all of them are warm(not hot really) except for:

Kickstart
Gary
74LS244 (x2)
74LS373 (x2)
74F244 (x2)

All of these are either cold or not warm enough for me to notice.

Overdoc · 17 March 2004, 23:45

hmm, does the Caps-Lock not even shortly blink on powerup ?
Maybe your Amiga doesn't get a reset signal ?
What if you detach the keyboard ?
I had one keyboard that would work on one Amiga 500 while it would cause another A-500 to stay just black !

19 March 2004, 00:02

No blink on the caps lock at all... The disk LED seems to light only quite dimly when I look at it now... So anyway I tried power up without the keyboard but no change.

Overdoc · 25 March 2004, 15:22

Hmm, no idea, black screen is always some kind of trial and error game....

What you can do is check the power supply if it puts out the correct voltages.
Then you can swap both 8520 CIA chips against each other, although I don't think they are bad because I still think there is some problem in the memory because the problem happened when you tried the expansion, but who knows ?

For further diagnose I for myself then would simply try each chip seperately in another Amiga. Thats the big advantage of A-500s over C64s since in the A-500 every chip is socketed

This method usually is the fastest way

25 March 2004, 16:18

Well I was planning to buy another A500 for harvesting parts so I may as well try that. If I can get hold of a decent multimeter I will test the PSU also. Thanks Overdoc!

Mangar · 26 March 2004, 02:19

Being from North America, and having a taste for Euro games back in the early 90's, I can tell you the Fat Agnus chip on some revisions of the A500 sold in the US and Canada could not switch to PAL mode.

My A500 was like that. I had to replace the Fat Agnus chip before being able to switch to PAL mode.

Guarantee your a500 works great in NTSC mode.

Jope · 26 March 2004, 09:47

Quote:

Originally posted by Mangar
My A500 was like that. I had to replace the Fat Agnus chip before being able to switch to PAL mode.

Are you sure it didn't have a 512k (OCS) Agnus? ECS Agnuses should be able to switch modes always.

26 March 2004, 11:01

Quote:

Originally posted by Mangar
My A500 was like that. I had to replace the Fat Agnus chip before being able to switch to PAL mode.

Guarantee your a500 works great in NTSC mode.

Possibly that is true... it is an NTSC Agnus chip alright. But I had a picture, albiet very briefly, the first time it powered up. I'll be sure to get a PAL A500 the next time, at least so I can eliminate that as a possible problem.

Computolio · 18 April 2004, 10:45

I've had this problem before. Black screen means fried CPU, "Agnus", or clock crystal.

However, when it happened to me, I could usually get the machine to work again by pressing down on all the chips. Unfortunately, there came a time whan that fix would no longer work and I wound up getting a new one.

07 March 2004, 18:39	#1
Fat_D Posts: n/a	Problems with my new old A500 Hi, I recently bought a refurbished A500 from a guy on eBay. I've lurked a bit on this board in the hopes of finding a solution my problem but so far I haven't had much luck. Ok so I'll try and give as complete a story as possible... Bought the Amiga from the US and got a faulty european power supply. One email later I get a replacement which seems to work. I also fitted a 512k Technoplus Amiram module. This didn't fit so well and on closer inspection had what I think is a broken capacitor on it. On first power up with this poorly fitted ram and the new PSU I got a somewhat corrupted looking "insert disk" image on the screen. After I inserted Workbench 1.3 I briefly saw what I guess was a workbench startup screen with mouse pointer. This then changed to a green screen and stayed that way. Each subsequent power up resulted in just the green screen which I understand can mean a problem with the chip ram or with Agnus. This is where things go nasty. I decided to open up the Amiga and I very carefully removed and reseated the Agnus chip as well as a few others. I also ditched the nasty RAM board. Power up now results in a black screen. I have no real idea what has happened at this point. I know that most of the chips are warm when the Amiga has been powered up with the exceptions of Gary, Kickstart and the chip RAM. Phew. Sorry, I realise that the above is something of an epic. I'm hoping someone can help me out so I can become a productive member of the Amiga community Last edited by Fat_D; 07 March 2004 at 20:22.

15 March 2004, 14:12	#9
Fat_D Posts: n/a	This is something I did check quite early on- whilst Agnus does get warm, it's no warmer than any of the other chips... My board is one of the earlier revisions so I have 16 ram chips. These all remain cool, they don't seem to warm up at all. Not really sure what that means! I'm not sure I know what the TTLs are, so I will figure out where they are and check them next. There is something else which may or may not be significant. Both of the LEDs on my keyboard remain lit constantly on power up. The caps lock LED remains dark though. [EDIT] I have checked the chips again and all of them are warm(not hot really) except for: Kickstart Gary 74LS244 (x2) 74LS373 (x2) 74F244 (x2) All of these are either cold or not warm enough for me to notice. Last edited by Fat_D; 15 March 2004 at 20:57.

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07 March 2004, 19:22	#2
Amiga1992 Registered User Join Date: May 2001 Location: ? Posts: 19,645	Dumb check but, have you reseated the chips in its correct position? Hope you did. And why did you connect the RAM board if a capacitor was blown? That surely hurted the Amiga somehow. The moment the gfx were corrupted you should have removed that thing Let's wait for overdoc to come and give more hints (hey he's Dr. Commodore )

10 March 2004, 11:28	#4
Overdoc Commodore Collector Join Date: Aug 2001 Location: Austria Age: 53 Posts: 944	Well, black screen can happen from almost any part in the computer if it is damaged too far ! But from your description the problem seems to have been cause by the ram board. So, this means Agnus, RAM chips or some of the other memory associated chips ( like the 74LS244 ) might have problems. I would say first check if you reseated every chip correctly ? Are all chips inserted in the right direction ? Is the Agnus socket still ok ? ( it can easily break when the Agnus is removed ! ). Also, is the diagonal edge on the Agnus facing the diagonal edge on the Agnus socket ? Remember that the print on the Agnus chip most of the times is facing to the left or right, sometimes also upside down if I remember correctly, so it doesn't mean anything for the correct fit of the Agnus ! Hard to say what exactly might be damaged or if it is just a bad contact problem, but the distorted startup screen definitely point to a Agnus problem ! I have had similar problems with an Agnus chip once ! ( one pin had bad contact to socket and contact with another pin ) Also, check if you might have bent some pin on the edge of the Agnus ? Sorry, that's all hints I can give you right now....

10 March 2004, 12:31	#5
Fat_D Posts: n/a	I'll have a good look when I get home and let you know how I get on! Thanks Overdoc!

14 March 2004, 17:59	#6
Fat_D Posts: n/a	Well, no joy I'm afraid. I must have done some serious damage. Fat Agnus is correctly seated and the socket appears fine too. It this rate I'd be happy to get back to a green screen. At least I know what that means... Any further suggestions or is it time to just buy a new A500?

14 March 2004, 18:02	#7
Fat_D Posts: n/a	I just read another post about RGB>Scart leads. I'm using one of those but was also was using it when I got the disk screen and the green screen... So unlikely to be a factor but thought I should mention it.

15 March 2004, 12:48	#8
Overdoc Commodore Collector Join Date: Aug 2001 Location: Austria Age: 53 Posts: 944	Hmm, have you done the heat check, yet ? If the problem has to do with the Ramcard, then it must be someting which has to do with Ram, Agnus or one of the TTL chips connected to ram. Also the green screen points to this. Just Leave it on for a while and feel if any of the Rams or any of the 4 (?) TTLs get hot ?

17 March 2004, 23:45	#10
Overdoc Commodore Collector Join Date: Aug 2001 Location: Austria Age: 53 Posts: 944	hmm, does the Caps-Lock not even shortly blink on powerup ? Maybe your Amiga doesn't get a reset signal ? What if you detach the keyboard ? I had one keyboard that would work on one Amiga 500 while it would cause another A-500 to stay just black !

19 March 2004, 00:02	#11
Fat_D Posts: n/a	No blink on the caps lock at all... The disk LED seems to light only quite dimly when I look at it now... So anyway I tried power up without the keyboard but no change.

25 March 2004, 15:22	#12
Overdoc Commodore Collector Join Date: Aug 2001 Location: Austria Age: 53 Posts: 944	Hmm, no idea, black screen is always some kind of trial and error game.... What you can do is check the power supply if it puts out the correct voltages. Then you can swap both 8520 CIA chips against each other, although I don't think they are bad because I still think there is some problem in the memory because the problem happened when you tried the expansion, but who knows ? For further diagnose I for myself then would simply try each chip seperately in another Amiga. Thats the big advantage of A-500s over C64s since in the A-500 every chip is socketed This method usually is the fastest way

25 March 2004, 16:18	#13
Fat_D Posts: n/a	Well I was planning to buy another A500 for harvesting parts so I may as well try that. If I can get hold of a decent multimeter I will test the PSU also. Thanks Overdoc!

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26 March 2004, 02:19	#14
Mangar Got the fever back Join Date: May 2001 Location: Toronto / Canada Age: 52 Posts: 288	Being from North America, and having a taste for Euro games back in the early 90's, I can tell you the Fat Agnus chip on some revisions of the A500 sold in the US and Canada could not switch to PAL mode. My A500 was like that. I had to replace the Fat Agnus chip before being able to switch to PAL mode. Guarantee your a500 works great in NTSC mode.

18 April 2004, 10:45	#17
Computolio Registered User Join Date: Apr 2004 Location: California Posts: 174	I've had this problem before. Black screen means fried CPU, "Agnus", or clock crystal. However, when it happened to me, I could usually get the machine to work again by pressing down on all the chips. Unfortunately, there came a time whan that fix would no longer work and I wound up getting a new one.