AMS DMX 15-80 card question

[mrzoo]

Hi,

Have some problems with an AMS DMX 15-80 where the device gets really hot.
I think one of the cards loads +5V too much.

I have checked all the cards between +5V and 0V and the dmx27 called mcb4 card might be the problem. It has 46ohms between +5V and 0V.

Or might it be correct value?

/Peter

 

[radardoug]

You could have a faulty tantalum cap, very common on AMSes.

 

[David Kulka]

Are you sure the fan is working right? They often start to run slow after they age.

Measure current on the 5v rail if you can. It shouldn't be more than about 6 amps, though this depends on how many cards are in the unit. If you think a card might be drawing excess current measure current on the 5v rail and carefully unplug cards one at a time so see if any one of them makes a major difference. Be sure to power down between each measurement.

46 ohms suggests about 100ma which isn't excessive, but resistance while powered down might not be an accurate indicator and the actual load when the card is powered up might be different.

 

[psych60s]

Once have on the bench a 15-80S with bad connections around fuse holders, and old wires about to break. Because of these bad contacts and wires, more heat was generated (the fuse holder was VERY hot). Something that is easy to check, as it could add more heat to the normal heat.

 

[David Kulka]

The 5V fuse holder is under rated and is a common failure. We would always substitute a pigtail fuse soldered directly to the motherboard.