Clay Paky scan lamp cycling

[Mr Steve]

Hello,

 

One of my Miniscan HPEs is playing up. It's fine for about 20-30 mins, then the lamp goes out. After 10 minutes it restrikes. The lamp was fairly grey so I had assumed it had a failing lamp that was cycling. New lamp fitted; problem still exists.

 

Both fans over the lamp and effects areas are functioning so I presume it's not legitimately overheating. Will it likely be the thermal sensor that's at fault, or can this sort of problem be symptomatic of a fault with the discharge lamp circuit/ballast etc?

 

Any advice welcome, as ever. Thank you!

[Stuart91]

I sometimes had issues with the interlock switch on the removable rear panel. They would behave perfectly and then trip five minutes before doors. My assumption was that fan vibration was making them misbehave.

 

However if the timings are more regular it is more likely that the problem lies elsewhere.

[Jamtastic3]

I've had Miniscan's for years. I've currently got one doing the exact same thing - moves about and all, fans spin but the lamp goes out after 20 minutes and then comes back on etc. My only thinking is that even though the fans are spinning, it's still reaching a temperature high enough to shut the lamp down.

It could be that one of the fans is lacking a certain rpm but still appearing to spin fast. I haven't replaced the mains fan in mine yet to see if this is the case but I have noticed that if the room temperature is a couple of degrees lower, the lamp stays on longer. Logic really but my main guess.

 

The other thing to check is that the mains fan isn't shutting off, fixture overheats, lamp goes out, fan starts up, lamp comes on, fan dies 10 minutes later, overheats, repeats.... etc.

This usually means you need to change the fan.

[Mr Steve]

Show time is over now, so I will pull it down and go through it step by step to see what's going on. Thanks you two.

[timsabre]

I have had this problem on other fixtures and it has been a faulty thermal trip - tripping at a lower temperature than the rating. They sometimes seem to do this with age.

I don't know if the miniscans have thermal trips, but if they do it would be worth checking out.

[Mr Steve]

I believe they do. I think about 4 years ago someone mentioned on here that you have to take the entire thing to pieces to get to it.

[stuart.thompson]

Sounds to me either a faulty fan so fixture not cooling down correctly or a fauty thermal. Check fans, if they all working fine then swap out thermal switch.

[niclights]

They are easy to get to. The units are well put together and it is possible to access everything without much effort.

There are two possible locations depending on model version.

 

If the lamp access cover runs the entire length of the unit and has two air exits then it is on the light baffle over the lamp and is immediately accessible after removing the cover.

 

If the lamp access cover is just the back half and there is only one air exit on the fixed section the thermal switch is on the underside of the lamp tray:

 

- Remove lens

- Remove lamp access cover

- Remove lamp

- Remove the whole top cover (4 machine screws w/flat washer)

- Remove the light baffle (2 self-tapping screws)

- Remove the two lamp terminals and pull back to the other side of bulkhead (1 self-tapping screw each)

- Remove nut and lock washer holding ignitor to bulkhead

- Remove bulkhead (2 machine screws w/flat washer & lock washer)

- Remove bulkhead (push ignitor bolt thread back so it clears)

- Lift lamp plate out (four machine screws w/flat washer & lock washer)

- Thermal switch is on the underside

 

Note you can probably get away without removing the lamp & terminals but it may be a bit fiddly.

[Mr Steve]

Many thanks.