Mac 575 lamp gremlin

[iDan]

Hi,

We were given a pair of mac 575 krypton spots a while back by a local theatre who were upgrading their stock - being an impoverished little college theatre, I gratefully took up the offer of some free movers regardless of their age. One works fine, the other has lamp issues. It will strike fine but cut out and display 'HOT'. Sometimes this will happen after ten mins, sometimes it will go a full day before playing up. After leaving it to cool for a while (usually left running so the fans can do their job) it will restrike happily but the same problem will reoccur. Occasionally it will also show the LERR (lamp error) message before cutting out and showing HOT. 

 

Here's what I've tried so far to no avail (all according to the manual)

- verified that ac voltage a frequency are correctly set on the ballast for UK mains (230V @50Hz)

- swapped the lamp for the one from the working unit

- cleaned the head and base of the fixture with a low pressure air gun

- operated the fixture in both warm and cool environments to see if ambient temperature makes a difference

 

Its worth mentioning that when we received these fixtures, the faulty unit had a 15amp plug on it suggesting it had been plugged into a dimmer system - perhaps this did some damage? I put it back to a standard 13amp plug.

Appreciate its an old unit and may just be time for retirement or kept for spares but I'm keen to explore possible solutions first. 

 

TIA

[DrV]

That may be the lamp on detector. There's a little PCB with a three legged chip on it made of transparent(ish) plastic. This is somewhere in the head such that the light shines on it. It will be connected with a three way molex kk connector. Check the connector and the solder joints on the PCB. You could also swap with your good unit.

Edited March 3, 2023 by DrV

[adam2]

It might be worth trying it set for 240 volt mains, not 230.  The change from 240 volts to 230 volts was largely a theoretical change. The actual measured supplied is still 240 volts most of the time in most places. And can be 250 volts if close to the transformer.

[indyld]

The described symptoms can be the lamp losing power, however momentarily. The LERR can be something else. 

I've had fixtures that display this symptom simply because of a break in the mains in that didn't last long enough to reset the fixture. But any loss of lamp power will do it. 

If the problem is very intermittent, it will be harder to track down. For swap outs, try the ballast if you have another one. 

Edited March 3, 2023 by indyld

[tonytech]

I had a MAC250 that started coming up with HOT errors.

Turned out to be the wiring to a thermal fuse situated behind/above the lamp hidden in a section of metalwork.

The wiring was in heat protective sleeve, but had become brittle and crusty.

[iDan]

Thanks all. Not had a chance to get the fixture back on the bench yet, but you’ve given me some good starting points.