Help with a strange fault on a Pulse CD player

[paulears]

About 18 months ago I bought a Pulse 1U rackmount CD player, and it developed a fault - the lights started to flash and it wouldn't work. I sent it back to CPC for repair and bought an identical one because it had just the right facilities. The new one didn't flash but had a peculiar rumble and fuzziness to one channel. The other came back from CPC no fault found. I put it back in the rack and forgot about it. This year my new sound op tried to use them and reported similar problems. I told him I'd had the same problem last year and to not worry, use the other players.

 

I've brought them both back home, with the intention of either attempting to cannibalise them both, or just dumping them - but here they work absolutely fine! They've been on for 4 days playing on repeat and both sound great, no lights flash and I'm stuck. I've removed all the equipment from the venue - so cannot go back and try them there, but I cannot make them fail. They've had a good shaking, tapping and vibrating here - and they are both rock solid.

 

I just can't work out what could make them both have repeatable, but different faults in the venue, but not here. They're metal cases, have IEC mains connectors - so what on earth could be going on?

 

Probably I am not going to solve this one - but maybe somebody else has had a similar weird, location based fault?

[david.elsbury]

Low voltage perhaps at the venue? Or high voltage?

 

Had an issue last month with some small powered speakers that hummed like nobody's business, at 206 volts... we moved them to a different socket in the venue, and metered just 216 volts, but they still worked... it was suggested that the regulators in the power supplies might not be able to handle the lower voltage we had...

 

2c etc :)

David

[Brian]

N-E fault in the venue? Or at the very least, interference across N-E.

 

There's a scenario I've been investigating recently where some equipment, designed as Class 2 but fitted into a metallic enclosure, might be susceptible to N-E voltages.

[ojc123]

This may be irrelevant but...

...I have one of the CDP50 players. I got it about 2 years ago. It plays fine. I discovered on PAT testing before installing it that it wasn't earthed. It is earthed now and works fine. I don't know if it worked when it was unearthed because I didn't use it till it had been tested and sorted. CPC are aware of this and were very helpful. If an unearthed player was in a rack and there were other odd earth things going on then it might cause problems. I'm not knowledgeable enough to be able to predict the problems. Just a thought.

[paulears]

A couple of things jogged my mind. There is a known N-E fault in the venue - that could not be cured. Dressing room heating. Throwing the lever to turn them on frequently produced a hum on sound systems powered from the single phase panel SR. Our own sound system seemed immune, but some visiting companies had this problem. One firm of electricians doing the annual inspection suggested the E-N fault, but couldn't fix it. As the issue seemed to only impact on some systems, I got a 3 Phase outlet put onto the SL busbars, that are directly above the intake room, and we have a distro that provides power from that side for visiting people's kit. This seems to be unaffected by the dressing room heating being turned on.

 

The sound system in the venue is powered from the supply that occasionally caused the hum issue. So if the neutral is drifting away from earth, it could be my problem? Maybe? Can't do much until next year.

 

Just to check - I'll put both on the tester, just incase OJC's suggestion is another excellent one.

 

Thanks for the ideas folks!