PATs on CSI followspots

[Phosphene]

Have been contacted by a venue operator whose gear has been tested by a domestic electrician, who has issued a fail for a pair of Strand Solo CSI followspots (22-526-00)

Superficial examination and metering reveals no fault.

Does the internal circuitry of a CSI unit make it likely that a basic plug and play test would show a fail even if in good order?

[Don Allen]

His pat tester may give a fail indication as the lamp appears open circuit, do you know if it was an earth fail or an insulation fail ? An open circuit lamp gives an insulation fail on my Metrel 3309.

[Phosphene]

We haven't any info on why he has put fail stickers on, however metering (as opposed to a plug and play tester) seems to show a high (of the order of several Kohm) resistance path between earth and live. This is the same for both lanterns and makes me suspect there's something inherent in the design of the circuitry.

[Jevans]

I can't claim any knowledge of those spots specifically, but I'm aware of a number of devices where there's high value resistors between line/neutral and earth. This should be called out in the user manual. For example I've definitely seen a 6 way dimmer pack with a ~100s of kOhm resistor between neutral and earth which fails an insulation test, but the resistor is intentional - either for EMI suppression or surge suppression, can't remember which! So this may be a similar scenario. 

[DrV]

9 hours ago, Jevans said:

For example I've definitely seen a 6 way dimmer pack with a ~100s of kOhm resistor between neutral and earth which fails an insulation test,

Some Strand Act6s have this.

[DrV]

On reflection it is probably a resistor across each of the Y caps so you don't get a shock if you pull the mains out at the to of a mains cycle and touch the pins. We used to have a Kenwood 'scope that didn't have the resistors. Ask me how I know!

[AncientLight]

I'm afraid this soon will become irrelevant, as there a few if any lamps remaining for sale. They haven't been made for years, and I think by now most remaining stocks of both CSI and CID have been hunted down

[Jivemaster]

Somewhere I should have a box of 10ish of either CSI or CID lamps supposedly 575w iirc. They were intended for some NJD waggly mirror lights. If they have value to anyone, speak up and I'll ferret them out.

[IRW]

I seem to recall (it’s been a while since I last tested Solo’s), that there’s a neon power indicator on the ballast, or something else that caused (maybe) funny insulation resistance results?

[Andrew C]

AND... Isn't there an indicator for "good earth" on the ballast of lantern*?  I wonder how that plays with PAT.

 

* it might be the SIL that I'm thinking of...

[IRW]

On 6/9/2023 at 2:45 PM, Andrew C said:

AND... Isn't there an indicator for "good earth" on the ballast of lantern*?  I wonder how that plays with PAT.

 

* it might be the SIL that I'm thinking of...

Maybe that’s what’s in my head actually…a little green thing?

[pmiller056]

I'm not familiar with these fixtures or the internal workings of them. When PAT testing I have come across older non-consumer equipment with electronic power supplies where there is a varistor-type surge suppressor connected between the live conductors and earth. These will cause the equipment to fail a 500V DC insulation test. They will usually pass a 250V DC insulation test (I'm not comfortable relying on such a low insulation test voltage for 230V AC powered equipment) and a leakage current test (unless there is an unusual mains powerline filter too....).