Trouble Replacing MSR 575/2 Bulb

[Stu Mannix]

Just received a couple of Mac 500s & Mac 600s. All worked fine for a few weeks. Then bulbs blew in all but one fixture.

Bought and changed bulbs (not touching the glass of bulb at all). But three blew again.

 

Is there something else I should know about changing bulbs apart from not touching the bulb at I fit in a Mac 5/600?

 

Any help/advice is gratefully recieved.

[pscandrett]

What do you mean by the bulbs 'blew'? IIRC those sort of discharge lamps degrade, and then 'blow' in a big explodey expensive mess - which is why you replace them at a certain lamp-hour-usage rather than when they 'blow'...? Do you just mean that the lamps fail to strike/turn on now?

 

It sounds a bit coincidental that they've all stopped working at the same time. Have you checked your incoming power supply? Have the environmental conditions changed?

[stagemanagement]

Have you tested the lamps to ensure they are actually blown?

 

It seems very unlikely all those lamps would fail so quickly; maybe an issue with the temperature sensors in the heads which are cutting off the lamp for protection?

MAC 500/600's are pretty old units now, so it's more likely component failure than lamp failure is the root cause here.

[timsabre]

What is the origin of these fixtures, might they have come from somewhere with different mains voltages? On these old fixtures you have to select the right voltage settings by swapping terminals on the ballast inside (unless they are E versions which have electronic ballast)

 

MAC600 manual says

MAC 600 (magnetic ballast)

1. Disconnect the MAC 600 from AC power. Remove the top covers.

2. Find the correct transformer and ballast terminals for your AC supply in the table below. Consult a

qualified electrician if you do not know the AC frequency and voltage.

3. Locate the transformer: it is on the left end, near the power switch. Move the BROWN and RED transformer

wires to the correct terminal. The terminal number is printed in front of the connection tab.

4. Locate the magnetic ballast: it is on the opposite end from the transformer, near the control panel.

Move the BROWN ballast wire to the correct terminal. The terminal number is printed in front of the

connection tab.

5. Replace the top covers before applying power.

 

Transformer Magnetic Ballast

Volt Term Setting Terminal

210 V 4 200 V / 50 Hz 7

210 V 4 230 V / 50 Hz 10

230 V 6 230 V / 50 Hz 10

230 V 6 245 V / 50 Hz 12

250 V 8 245 V / 50 Hz 12

210 V 4 208 V / 60 Hz 4

230 V 6 227 V / 60 Hz 7

[Stu Mannix]

Thanks for all the replies.

 

By 'blew' I meant failed to strike. Took bulb out of fixture to find the bulbous part of bulb very cloudy. It IS a tad suspisious that three 'blew' in one action.

 

Incoming power supply not an issue for past 7 yrs. They are fed from 2x 10amp C Form connectors. Power flow has a surge protector on it too.

 

Origin of fixtures is that they have been bought from a hire company, and been used in same country, county, and venues for many years with no problems at all.

 

I just wondered if there was something I didn't know about changing the bulbs in a Mac 5/600 fixture apart from not touching the bulb?

 

Thanks in advance.

[pscandrett]

The bulbous bit on a lamp like that being cloudy is quite normal; various elements evaporate during use, and when it cools down they deposit themselves on the inside of the lamp again. They'll burn off next time the lamp is struck (this is one of the processes happening when the lamp is 'warming up').

 

My bet is on something in the lamp striking circuitry - either the unit isn't telling it to strike in the first place, or the actual circuit has failed. Do you hear a 'click' from the relay when it tries to strike, for example?

[Stu Mannix]

The bulbous bit on a lamp like that being cloudy is quite normal; various elements evaporate during use, and when it cools down they deposit themselves on the inside of the lamp again. They'll burn off next time the lamp is struck (this is one of the processes happening when the lamp is 'warming up').

 

My bet is on something in the lamp striking circuitry - either the unit isn't telling it to strike in the first place, or the actual circuit has failed. Do you hear a 'click' from the relay when it tries to strike, for example?

 

I hadn't noticed a click. But will have a listen. Thanks.

[timsabre]

I would suspect ignitor failure. The ignitor is a cylindrical metal part about 50mm long, 25mm dia with a threaded stud on one end for mounting and terminals on the other end. It often becomes intermittent (will strike cold and not hot) before giving up entirely. If you have a working unit try swapping it over (beware very high voltages when operating)

 

like this (the left hand bit)

 

In the mac600 it's on the colour wheel assembly in the head. Never had a 500 in bits but from pictures it looks like it's in one of the side arms of the yoke. In that case the cabling runs through the yoke pivots so could also be a worn cabling problem.

[Jivemaster]

Sometimes when well (over) used the connector springs in the lamp holders become weak and then they arc and heat the pin til it burns. A burned lamp holder will burn the pins on the next new lamp, til someone throws the whole fitting away -all for the changing of a new lamp holder.

 

Look carefully at both pins on the lamps that you have rejected -maybe use a magnifier. Little black patches at the contact point may show, may be cleanable, but DO indicate that the lamp holder needs replacing.

 

PS (added) When a discharge lamp truly blows there is likely to be lots of damage to the fitting. Any igniter will likely provide high frequency pulses in the order of 7 - 25Kv -they kill.

[DrV]

I would suspect ignitor failure. The ignitor is a cylindrical metal part about 50mm long, 25mm dia with a threaded stud on one end for mounting and terminals on the other end. It often becomes intermittent (will strike cold and not hot) before giving up entirely. If you

In the mac600 it's on the colour wheel assembly in the head. Never had a 500 in bits but from pictures it looks like it's in one of the side arms of the yoke. In that case the cabling runs through the yoke pivots so could also be a worn cabling problem.

No, it's in the head and is a right PITA to replace!