Dimming PAR36 30W Pinspots

[DanSteely]

Hi All,

 

The show is We Will Rock You and I'm going to make the laser cage using 8x Pinspots but would like to power them via a 10A dimmer channel..

 

Will it trip the dimmers MCB or will it damage the transformers in the pinspot? The fade time will be probably 500-1000ms. Will the pre-heat voltage cause a problem?

 

If a dimmer can't be used we can always switch the hard power supply.

BTW: I have a small 4 channel 5A Showtec dimmer pack which I use in switch mode to power a DF50 and on a separate channel fans to push the mist about - could this be used?

 

Many thanks.

[timsabre]

Stage lighting dimmer packs will dim pin spots no problem.

[DanSteely]

Thanks Tim

[timsabre]

I did once blow up the transformers in a load of pinspots using a Pulsar Zero 3000 sound to light unit. That had a setting called "shimmer dim" where it only put through one half cycle of the mains.

 

Basically uneven switching of the positive and negative cycles of the mains is your enemy with pinspots as this gives an effective DC offset into the transformer which will kill it. A "good" dimmer will not do this.

[Andrew C]

Ummm... no. I've seen LOTS of pinspot transformers cooked by dimmers. The Betapack may be OK, JTMs were NOT.

[timsabre]

Ummm... no. I've seen LOTS of pinspot transformers cooked by dimmers. The Betapack may be OK, JTMs were NOT.

 

Huh? I've dimmed lots of pinspots on Strand JTMs and also on Mini 2's which were very similar in design.

Where did he say it was a betapack?

[Andrew C]

Where did he say it was a betapack?

Dunno, must have elided two threads in my head.

 

No, wait... In the sub-title on the index page!

 

Possibly a different tx in the ones you've dimmed, perhaps the ones I had to repair were left on for long periods at a dim level? I don't know, but have repaired over a dozen (that we got free as they were dead), and they now live in the same town as the OP...

[ianknight]

BetaPacks should be good with Pinspots, used them myself a few times with other transformer'd loads.

 

If you want to be sure that the curve is ok then use a load lamp with them to 'tame' them (but it's not really needed) something like a profile with a beam split gobo over the top of the pin beams would be "in keeping" and not clutter up the rack room or fly floor.

[timsabre]

Where did he say it was a betapack?

Dunno, must have elided two threads in my head.

 

No, wait... In the sub-title on the index page!

 

Seen it now... it was in the subtitle of the thread.

Thyristor dimmers like the JTM was can be uneven on the pos/neg half cycles, because there is a separate thyristor and drive circuit for each polarity. This is what creates the DC offset which cooks transformers. This should be less of a problem with triacs.

[David A]

there are different grades of transformers in pinspots, some will cope with the d.c. content, others not.A ballast load will usually solve the problem but I would avoid low dimming levels or "pre-heat" settings, I would scrap a dozen every year due to burn out, it's not cost effective to repair them unless your labour is free.