Voltage drop, Amiga 500

[Misko78]

I had a significant voltage drop from 4,85V on power connector to 4.6V on floppy connector. Here is what i've done so far.

1. Packed RT-50B into an Amiga PSU case. Same thing, but more severe, new PSU was 5,01V and it still drop to 4,65V so i bump up the voltage to 5,3V to have 4,8V at floppy connector.
2. Changed all capacitors with new ones, and triple checked polarization
3. Did a continuity test all over the board, no problems at all.

Everything works fine otherwise, i use the HC508 accelerator and Gotek drive.

[OldAmigan]

Hi Misko78,

Did you get any resolution of this problem?

Were those voltages you gave with the PSU connected and the Amiga powered on?

Did you get the same dropped voltage at the PSU at this time?

It sounds as if something in the Amiga is drawing too much current. You could try removing the accelerator and retrying.

Fred

[Misko78]

Originally Posted by OldAmigan

Hi Misko78,

Did you get any resolution of this problem?

Unfortunately not.

Originally Posted by OldAmigan

Were those voltages you gave with the PSU connected and the Amiga powered on?

Yes Amiga is powered on and voltages varies a lot, i did monitored it while using it, I connected a multimeter and played a game and some demos and it goes from 4.65V low to 5.0V

Originally Posted by OldAmigan

Did you get the same dropped voltage at the PSU at this time?

No, this PSU is fine on other Amiga.

Originally Posted by OldAmigan

It sounds as if something in the Amiga is drawing too much current. You could try removing the accelerator and retrying. Fred

It's the same with accelerator and without it. Yes i guess something is drawing too much current, chips are warm to the touch, everything works fine. Maybe one of the new capacitors is dodgy.

[Daedalus]

What about the power connector itself - perhaps it's making poor contact and the excessive resistance there is causing the drop? I would measure the potential between the PSU's 5V output and the 5V as close as possible to the connector on the motherboard, and see if the drop is there. I would then do the same for the ground connection. It's not uncommon for those connectors to get tarnished and worn...

[Photon]

1. Have you measured drop with original PSU and nothing attached but PSU?
2. Does the drop cause problems, if so which?

Can't find HC508 MKII power draw quickly, original is 2.5A which leaves 1.5A for HC508.

[Misko78]

Originally Posted by Daedalus

What about the power connector itself - perhaps it's making poor contact and the excessive resistance there is causing the drop? I would measure the potential between the PSU's 5V output and the 5V as close as possible to the connector on the motherboard, and see if the drop is there. I would then do the same for the ground connection. It's not uncommon for those connectors to get tarnished and worn...

Yes, i measured voltage at the power connector and the drop was there. I sprayed contact 60 into it and used a little bit of cotton on a toothpick to clean it. Now it is rock solid at 4,85V with original supply and 5,0V with Meanwell RT-50B.

Thanks for your help fellows!!!