A500+ won't boot - flashing power LED

[r_welfare]

Hi there

Bought an old A500+ from a boot sale to relive some old memories this morning.  When I got it home, powered it up but there is no screen output or drive clicking.  The power LED performs a cycle of one long and ten short flashes.

Looking at old posts on the subject here, it was suggested that the chips should be reseated or inspected for frying.  I've opened up the case but nothing seems to be hot or have fried and everything seems to be seated correctly.  Should I go around levering up the chips and reseating them anyhow?

Could the problem perhaps be with the power supply unit itself?  It makes a strange whistling sound just after it's turned off...

Any help appreciated!

Cheers
Richard

[Karlos]

Sounds like it could be a duff PSU. I had a gammy PSU on an A1200 do something similar. Nothing was damaged in the computer but one of the voltage rails had dropped low. This was due to a prolonged period of drawing too much current to feed various expansions.

Suffice to say the problem went away with a beefier PSU.

[Thomas]

The power LED performs a cycle of one long and ten short flashes.

This means that the CPU, the Kickstart ROM and one of the CIAs are ok. There is another problem which causes the Amiga to crash, reboot, crash, reboot, crash, reboot...

The reason for the crash can be seen by the color on the montor. The monitor should show all one color. The meanings of the colors are:

red - bad ROM checksum
green - too few or damaged chip ram
yellow - processor exception before the exeption handler is initialised (this is usually a software problem).

It makes a strange whistling sound just after it's turned off

Well, replacing an old power supply by a newer one is always a good idea. Especially if the new power supply is stronger than the old one.

Bye,
Thomas

[patrik]

@r_welfare:

The A500+ has a NiCd clock-battery that leaks and eats away the tracks of the motherboard when it gets old, you better check it.

Other than that, press firmly on all socketed chips as they have a tendency to work their way a bit loose from the sockets with time. Keep in mind that they might look seated, they wont literaly pop out of the sockets . Still, just press on them firmly.

The whistling from the power-supply might very well be that the laquer of a coil or a transformer isn't keeping everything still nowadays and thus gives of a sound. If so it is harmless and might silence when it reaches working temperature.


/Patrik

[Karlos]

Do you mean flashing or simply cycling between bright / dim?

In my dud PSU case, the LED appeared to blink on/off rather than the usual guru cycle of bright/dim...

[Thomas]

Do you mean flashing or simply cycling between bright / dim?

The older Amiga models (A500, A2000) always blinked on/off. The bright/dim thing was introduced on later models (A1200, A4000). I don't know about the A500+, though.

Bye,
Thomas

[r_welfare]

patrik wrote:
@r_welfare:

The A500+ has a NiCd clock-battery that leaks and eats away the tracks of the motherboard when it gets old, you better check it.

/Patrik

Patrik, you could be onto something here.  I whipped the case off and there's lots of 'fur' around the battery at the terminals.  Looks like there may be a bit of 'track eating' around some tiny components near the battery.  Is it easy/worthwhile to clean up?

Thanks to everyone else for your suggestions.  On the PSU front, I will try and borrow a friend's PSU from his A500.  I'm not getting any colours on the monitor at all.

[PaSha]

Thomas wrote:

Do you mean flashing or simply cycling between bright / dim?

The older Amiga models (A500, A2000) always blinked on/off. The bright/dim thing was introduced on later models (A1200, A4000). I don't know about the A500+, though.

Bye,
Thomas

The old A500/2000s, with RED power LEDs, behaved this way (LED completely off if the lp-filter was off). The slightly newer ones, with GREEN power LEDs, dim the LED instead of switching it completely off when the lp-filter was off.

-Paul

[patrik]

@r_welfare:

Yeah, you should remove the battery ASAP and clean away the stuff that has leaked onto the motherboard so it doesn't eat more of it.

Quotes from this battery repair guide:
"Obviously the battery needs to be removed. If you simply can't be knackered fixing the computer, the least you should do is remove the battery using a small pair of sidecutters to cut the 3 legs holding it to the motherboard. This will stop further corrosion."

"Using a combination of the toothbrush and rag, clean the visible corrosion damage from the board using the methylated spirits or isopropyl alchohol.
You can scrub quite hard with the toothbrush with little risk of damage. The components and soldering are quite robust."

Btw, the battery is not needed for the Amiga to function, so don't worry too much about replacing it.

Not regarding the battery, but also do not forget to try what I mentioned about pushing the socketed circuits into place as it is often the source of old Amigas not working.


/Patrik

[r_welfare]

Patrik

Thanks for your tip.  I will have a go at cleaning up the circuit board.

I've been round and tried pushing the chips down (I actually removed the ROM chip and re-seated it) but to no avail.

Richard

[Tomas]

Do you have equipment for checking the psu? like a multimeter of some sorts..

[r_welfare]

Don't have a multimeter...but I do know someone with a working A500 PSU.  A trip to him is in order!

I have now removed the old RTC battery (covered in fur...ugh) and cleaned up that area of the motherboard with methylated spirits.  All the chips seem to be correctly seated.  The machine still doesn't work...but on the upside, it's still flashing the same error so I haven't done any more damage :-)

[TheMagicM]

its probably not the PSU.  if its the mobo, let me know.. I have about 3 or 4.. dunno if they work..if they do I will find one and mail it to you if you're in the USA. (it not a A500+, just a stock 512k mobo)

[r_welfare]

As it was only £3, have bought a standard A500 motherboard from eBay.  Hopefully now I can get it working, should also mean I get to play more fun old games...

[r_welfare]

Well, a happy ending to the story - after retrofitting the machine with an A500 Revision 6A motherboard, it finally works.  Thanks to everyone for their help.  I'm off for a game of Hunter!