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Amiga computer related discussion => Amiga Desktop Audio and Video => Topic started by: amigakid on June 25, 2014, 08:04:47 AM
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I am stumped! I have been trying to get my old A4000 up and going. I bought another MB from Ebay (second one now) and all I get is a Red Screen immediately when it turns on. I don't remember but I thought there was a second or two delay when it powers on before the system check begins. I know Red means ROM problem, but the red screen comes on right when the power button is pushed, absolutely no delay. Also I have swapped them with 3.1 and 3.0 ROMs and still same thing. I am not sure but could the PSU be a problem? It is actually the only thing I don't have a spare of and the only common factor ... actually not true the CPU board is also the original, but I get the red screen when it isn't even connected. Ant suggestions would be great as I am tired of spending money on MBs and still not have a working A4000
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Also the CTRL+A+A does restart the Amiga ....kind of, when I have the HDD connected it spins up and the HDD light comes on for a sec and when I CTRL+A+A the HDD restarts, but the screen stays constant red, not even a flicker!
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This kind of thing is usually caused by some sort of data bus corruption. Typical causes are a missing ground from U891 (pin 10) or U891 corroded by a leaking RTC battery. Just unsolder U891 and remove all fast memory SIMMs and see if it boots to the insert disk screen. The system will run fine without U891, but as this is quarter of the data bridge for the fast memory, then you'll have no fast memory until you replace U891 and fix the associated tracks/vias.
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I am stumped! I have been trying to get my old A4000 up and going. I bought another MB from Ebay (second one now) and all I get is a Red Screen immediately when it turns on. I don't remember but I thought there was a second or two delay when it powers on before the system check begins. I know Red means ROM problem, but the red screen comes on right when the power button is pushed, absolutely no delay. Also I have swapped them with 3.1 and 3.0 ROMs and still same thing. I am not sure but could the PSU be a problem? It is actually the only thing I don't have a spare of and the only common factor ... actually not true the CPU board is also the original, but I get the red screen when it isn't even connected. Ant suggestions would be great as I am tired of spending money on MBs and still not have a working A4000
You putting in the ROMs the right way? Odd that they both don't work, would think it was a bad ROM.
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Yeah that was my initial thought! I shall try the U871 chip, never thought of that. Thanks for the replies I'll keep you all posted on if I get it fixed
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OK so initially I had the monitor on digital so I was getting the colored screen. On RGB the screen is a dark grey when it turns on. If I remember right the A4000 starts with that screen for a second the changes to a lighter grey then does the system checks. The screen doesn't change at all so I am thinking it isn't making it to the post. Could this be the PSU causing the issue? The HDD light does come on briefly and the CTRL A+A does seem to restart the unit (hdd spins down then back up, but power light or screen does not flicker at all).
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OK After testing the PSU (which seems to be alright) I inspected the 3640 processor card and noticed 2 of the caps have leaked. Anyone know where I can get replacement caps, or anyone have a working processor card they are willing to part with?
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OK After testing the PSU (which seems to be alright) I inspected the 3640 processor card and noticed 2 of the caps have leaked. Anyone know where I can get replacement caps, or anyone have a working processor card they are willing to part with?
You could buy an A3630 CPU board as these are easily available, affordable and useful for testing. But either way, it sounds as though you have a CPU board and/or main board fault so something is likely to need repair. No doubt you've checked the obvious, such as both main board clock jumpers are in the EXT position for the A3640.
From your first post; not sure how it's possible to get a red screen with no CPU card fitted as it's the CPU telling the video section to display the red screen. After power on, the CPU calculates the ROM checksum and compares it to the checksum recorded in the ROM. If they don't match, the CPU sets the video section to display the red screen. Is your monitor in known working condition?
The A3640 capacitors also have known issues (http://amiga.serveftp.net/A3640_capacitor.html), as do the ones on the main board.
Contact me for a repair estimate if you can't make any progress.
http://amiga.serveftp.net
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I usually buy all my electronics online at digikey.com
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The red screen was because I had the monitor on digital lol. Thanks for the site link I will take a look there. I been looking on Ebay for a replacement CPU, but haven't found one yet.
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Normal sequence:
Dark Grey
Light Grey
White
Error:
Red (indicates error in ROM)
Green (error in CHIP RAM)
Blue (error in a Custom Chip)
Yellow (680x0 found an error)
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This is so reminiscent of our trying to keep our A4000-based PAR stations functional. In the end we had to cannibalize so many corpses and pieces to try to keep the last couple A4000s functional. They're a really unfortunate design.
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Yes they are an unfortunate design. I have an Amiga 500+, 1000, 3000, cd32 and 2500hd and I have never had this much issues with any of them lol, but I am not giving up until she is up and running good.
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Yeah, it's rare that you find any selling second hand. Overheating is a big problem, whether you expand or not. We had to drill out the cases and put three and four extra fans because the PAR and TBC-IV would make the cases so hot you couldn't touch them. If I remember right, the 4000T wasn't as readily available and drove the per-station cost up more than we wanted, plus it couldn't fit on the monitor carts we had stationed around the studio.
Me and three other Amigans put the proposal together to build these things to take the strain off the bottleneck to our single Accom DDR. I think we built six or eight of them for the price of one Accom with about a minute or two of 601 playback for shooting animation, comp and render tests to. By comparison, I think each PAR had some 45min of footage on a 45Gb disk. I wrote the CSH shooter script that folks used on the IRIX side and another fellow wrote the ARexx script that my program talked to to handle conversion and clip management. It was great, until Commodore went tits up. Then it was like, almost on queue, boom, boom, boom we started getting failures.
The last couple that were still operational ended up being commandeered by the guys on our motion-control stages because once they found out one of our PAR stations could replace the 3/4" video setup they used to preview miniature moves they wouldn't give them back. Amiga4000 + PAR pretty much revolutionized the way miniature photography was done for a while, on True Lies, Apollo 13, Interview With the Vampire. By the time we got to The Fifth Element and Titanic I think the last of the Amiga PAR stations had died and had been replaced by an NT box with what replaced the PAR, the Perception Video Recorder.
Mine died after about a year of casual use, after the warrantee was up and not long after Commodore filed too. I think I was still paying for it a year or two longer on a, get this, Apple Credit Card (bought at Creative Computing in LA).
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wow seems you had quite a bit of experience with them, that is great. Yeah hopefully I can find a used, working CPU card for it. I will buy and replace the caps and hopefully get this one up and running also!.. Thanks for all the input!!
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Yeah, I was really bummed when my A4000 died. It was my favorite Amiga that I'd ever owned (A500, two A3000s, and an A1000). I didn't even own a computer for about a year after that. Macs were still just way too expensive and didn't run the software I wanted anyway. I was still against owning anything Intel for "religious" reasons so it wasn't until the first affordable DEC Alpha workstations became affordable that I took the plunge again, since a lot of other professional Amigans were going that way too for a few years.
I missed that A4000 though, and DPaintIV and Brilliance.
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Yeah I loved the A4000, prob my favorite, although I do really like my A3000 setup I have too. I wish I had a working CPU card because I have some software I been wanting to run and it is my only AGA box