A1200: now a PSU issue...

[Karlos]

Is it just the 1240 card and no other expansions that this happens with?

A slower fan implies to me that there is a voltage drop on one of the rails. As far as I recall the fan on the Apollo1240 is a 12VDC one. You are definately sure the +12VDC line is correctly wired up?

[Karlos]

Can you test the levels with the base A1200 and with the apollo attached? If possible chech the levels on the pins powering the fan and also on the floppy power header on the motherboard. If the fan is slower I'd expect the 12VDC line to  be low.

I wonder if something is pulling too much current through some  weak link?

[Karlos]

My A1200D is running from a cannibalised ATX PSU with no problems. You just have to ground the PS_ON line (grey I think, but seriously do not take my word for that).

[Karlos]

I never trust any of these particular so called "colours". Nobody ever offered me any tangible proof they exist :lol:

[Karlos]

Most likely your PC is drawing most juice from the 3.3v rail so that the 5VDC one has less impact on reliability.

[Karlos]

@starf81

Powering the A1200 motherboard via the floppy port is pretty common. My A1200T's motherboard is powered from the case PSU via this and also via all 5 voltage rails of the rear connector (most people just use this for the -12VDC line).

Naturally all other drives / fans are powered direct from the PSU too.

With this dual connection arrangement, less current has to flow throught any single point on the motherboard. Some accelerator cards (eg my BPPC 040 + BVision + RAM) can require quite some power, more than I would feel comfortable pumping through my ageing A1200 motherboard via a single place.

[Karlos]

starf81 wrote:

Could the Fast-Ata not working well without an accelerator card?

Possibly; I don't know for a fact. The Fast ATA probably doesn't give any real speed up on a bare 020 A1200 with no fast ram anyway and I doubt the creators of the hardware envisaged it being used in such a fashion.

[Karlos]

One of the pins on the oscillator should be 5VDC - you'd need to check the pinout for it though.