Power Supply not powerful enough

[Jherek Carnelia]

What would happen if I added an accelerator without having a powerful enough PSU?

Would it damage the mobo or just not work?

I have a standard lightweight A1200 PSU and I added a '030 with FPu (no RAM) accelerator. All was fine for a day and then the Amiga wouldn't boot properly - the floppy light came on permanently and the busy pointer wouldn't go away. Even with the accelerator and floppy drive removed it stays the same.

A knackered Amiga and a pi**ed off Jherek!

Is it down to the accelerator or just coincidence?

[RetroMan]

The standard A1200 PSU sometimes isn´t even capable of powering an A1200 AND a HD Get a 4,5A A500 PSU and will have no problems anymore

[Jherek Carnelia]

My point though Retro, is has the lack of power damaged the motherboard?

[RetroMan]

Thats not possible .... if the power would be too high, then yes ... but if you have a too small PSU, the complete Computer would just freeze ....

[Overdoc]

It is very unlikely that the overloaded psu has killed your board.
But it could well be possible that your psu is damaged now because of overload and now puts out lower voltage or not steady voltage, which fu%&s up your Amiga.

PSUs are built to supply a fixed voltage and can supply up to a certain number of amperes. Now if your machine is very powerful ( e.g. upgraded a lot ) it will draw more amperes from the psu than it is built for. Good and expensive switching PSUs then go into fail save mode, but the normal Amiga psus could get overheated and burned. ( at least I think so, I happily never lost one *knocking on wood* )

I'm going a bit off topic here but I just wonder. Does your accelerator work without ram on it? Mine doesn't, I just get 020 speeds without ram.

[Jherek Carnelia]

@Burseg
It did work, but the speed increase (as reported by SysInfo)was not all that much. I'm reluctant to fit it to my only remaining A1200 now.
Does anyone want to buy a Magnum Accelerator? :laugh :laugh

[Shadowfire]

Jherek,

It does depend on the design of the PSU, but for the vast majority of them, you can count on a series of events.

1. You will most likely hear a pretty loud buzzing from the PSU. This is the result of the semiconductors trying to sink too much current. If its buzzing louder than normal after the computer is on (see below), you can bet its going to fail, probably sooner than later.

2. The load on the PSU is highest when you first turn the PC on (when the hard disks are spinning up). If the buzzing goes away after the hard disks spin up, it's still not a good thing.

3. Most PSU's can, in fact, supply more current than they're rated for, and the computer will still work. However, as far as I know, NO manufacturers purposefully "underspec" their PSU's (although they *may* engineer a little bit of wiggle room)... so there will be SOMETHING inside there that will get toasted MUCH sooner than it otherwise would.

4. When a semiconductor burns up (as would happen in a typical PSU failure), one of two things can happen; either the semiconductor will "open up" (and this will result in the PSU going "dead") or it will "fuse" (which may be a VERY bad thing because the voltage regulation might not even be able to shut the power off - resulting in higher-than-intended voltages).

5. I've seen both types of failures. I've had a PSU "die" (which I subsequently resurrected) due to capacitor failure on the filter capacitors on the voltage rectifier (pair of 470uf caps which were each reading about 110uf after I disconnected them and checked them, if you care to know... there was visible signs of leakage too)... this resulted in the PSU not being able to supply enough voltage for the AMD Athlon in the system it was in (FIXED by replacing the capacitors- it was a very expensive PSU & worth my time to diagnose & fix). I've also had what I can only guess was a major "standby voltage" failure in another system, killed my network card and motherboard (my machine was off when I left for supper... came back to hear a loud buzzing sound coming from my machine's speakers, and the machine was "on" though not working).

6. I guess the whole point I'm trying to say is, if you think your PSU isn't beefy enough, don't risk it, you might toast your whole machine, and (with ATX power supplies) it can even happen when you're not even in the room with it and the machine is turned off.

[Jherek Carnelia]

Thanks for the info Shadowfire - I will buy a new PSU!

[Shadowfire]

Also, without any fast ram on the accelerator's board, the accelerator isn't going to buy you very much (if anything at all). the Amiga chip memory system is speced to have enough bandwidth to feed the custom chips and a 68000. Anything beyond a 68010 will be mostly wasted without extended 32-bit memory.