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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Munchkin on May 14, 2018, 01:11:48 AM
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Gotten quite inspired lately so I dug up my old A500 that's been in storage for about 20 years.
Connected the old GVP HD8+ and fired it up and everything went just fine, for a little while. After a few minutes running, at least seemingly, perfect it crashed with a lot of noise and a green screen with lots of artifacts.
Tried to reboot without luck so I turned it off and then on again and it booted up but this time with a lot of yellowish dots flashing around the screen. It got into the workbench then everything just went black. No power whatsoever it seems as the power led also went black and not even a hint of anything when I switched the power off and on again.
So, I suspect it's the power brick that's gone bad but I didn't have any instrument to check if there is any power coming out of it. Gonna go down to my car and get one tomorrow so I can check. Opened it up though and the fuse seems ok but I'll check that as well.
Am I on the right track here or might it be something else?
Before I tried to start it up I took the A501 out and removed the old leaky battery. Nothing had spread to the circuit board though but I gave it a bit of a clean up anyway. No new battery mounted.
It's an old 500 from 1988, modified with a newer Agnus so it uses the 501 memory as extra chip ram. Also has a VXL-30 with Ram-32 w 2MB. Besides that it's stock. If that helps.
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Try removing, cleaning, and reseting everything. If there was a "lot of noise" as you say, your hard drive might be toast.
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R.i.p
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Try removing, cleaning, and reseting everything. If there was a "lot of noise" as you say, your hard drive might be toast.
The noise came from the speaker in the 1084, not the hardware. The harddrive works just fine, well at least power is on and the harddrive spins. Can't check if it actually works before I fixed the power issue to the 500 but it worked just fine before the computer died.
I did check the fuse in the power brick though and that was fried, no contact at all. So, question is why it fried. Gonna take everything apart and reseat whatever can be reseated and then try again with a new fuse.
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Well. Got some new fuses, put one in and the first time I turned it on it went well, the second time I put it on the fuse blew on an instant.
Not connected to the 500 at any of the tests. I'm pretty sure the PSU is the problem then. Question is, is it worth to try and recap it and hope that does it or better to try and find some kind of replacement?
Googled around a bit and didn't find any pictures that looks just like mine do internally, I guess mine is a somewhat odd version?
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with that big transformer it doesnt look to me like a computer power supply. could that be that a500 bricks were built like that? is it a genuine one at all? looks a bit like do it yourself kinda thing.
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with that big transformer it doesnt look to me like a computer power supply. could that be that a500 bricks were built like that? is it a genuine one at all? looks a bit like do it yourself kinda thing.
It's genuine. I bought the computer myself back in 1988 and I've never done anything to the power brick, it came like that when I got it.
When I measure the voltages on the pins from the psu both the 5V and 12V fluctuates like crazy. I don't know if this is normal or not when it's not connected to the computer.
I don't know how likely it is that the transformer goes bad, I'm gonna recap the psu and see if that fixes the problem. I might have to recap the Amiga as well but for now I think the main issue is the PSU since i blows fuses even when it's not connected.
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check voltage at the transformer taps, see if they are fluctuating. if so, you probably have a bad transformer. if not, start checking caps.. and then the diods / rectifier.
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Beginning to feel it's better to just try and get a replacement power supply of some sort.
I did find a thread on another forum with info about the same power brick as I have and the ones that they talked about had problems with caps and/or voltage regulators. So, I guess that'll be my starting point.
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So, after letting it be for a few days I put a new fuse in, connected it and powered it up without the GVP HD8 connected. It seemd to work just fine, it sat there waiting for a disk to be inserted and I didn't see any artifacts on the screen either.
Turned it off and let it be for a few minutes, turned it on again and I saw some artifacts on the screen before the fuse went POP.
Does this indicate a cap issue in the PSU?
I mearsured the voltages with proper tools and I got about 5.45V on the 5V pin, 12.5V on the 12V pin and exactly -12V on the -12V pin, this when it wasn't connected to the amiga as well. No fluctuations to talk about really.
I did manage to measure a bit when it was on the first time while it "worked" and the 5V was rock solid while the 12V fluctuated betwen 10V and 12.5V. Don't really know where to measure the -12V though so don't know how that fared when connected.
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Does your GVP HD8+ use its own power supply? If not, there's little chance that old commodore cheapskate supply will provide enough amps for that. Anyway, put that old brick aside and make yourself a favor and make PSU of PC ATX supply. It will provide good service for years to come.
Use this source for your coversion;
http://www.ianstedman.co.uk/Amiga/amiga_hacks/Amiga_Power_supplies/amiga_power_supplies.html
Just my 'two cents' on subject. Good luck! ;)
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Does your GVP HD8+ use its own power supply? If not, there's little chance that old commodore cheapskate supply will provide enough amps for that. Anyway, put that old brick aside and make yourself a favor and make PSU of PC ATX supply. It will provide good service for years to come.
Use this source for your coversion;
http://www.ianstedman.co.uk/Amiga/amiga_hacks/Amiga_Power_supplies/amiga_power_supplies.html
Just my 'two cents' on subject. Good luck! ;)
Yes, it has it's own powersupply so that isn't the issue. It worked for years before I put the things away 20 years ago. I do know that PSU is on the weak side since it's the old heavy 2.5A one so it's no wonder it doesn't measure up to the load with the VXL-30 installed after 30 years.
I've been thinking about making that kind of conversion. Though, since it's gonna be a computer I take out and put away off and on I need to make some kind of enclosure for it to protect it from to much stress.
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Hmm. If I understand correctly this thing would do the trick?
https://www.meanwelldirect.co.uk/product/50W-AC-DC-Triple-Output-Desktop-Adaptor/P50A13D-R1B/default.htm
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Well. After a very thorough cleaning of both the A500, the GVP controller, both powerbricks and reseating of all socketed chips everything seems to work just fine. Not that anything was really dirty, at least not visibly, but I guess there was some bad contact or a short somwhere.
Been running it for about an hour now using the harddrive and not a sign of instability.
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Great news!!!
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Great news!!!
Very! It kinda feels like 1992 again when I got the HUGE 120MB harddrive! :D
I know I had a heatsink and a fan on the 030 back in the 90's but the fan died and I removed both. I know it's not all that dangerous, the 030's run quite hot, but I would feel better with some cooling on it, at least put a heatsink on.
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I know right?
My 030 runs hot too :-/