Showtec Compact PAR problem

[StopWatchingTV]

Hi,

 

I have a set of four ShowTec CompactPar 18 tri Mk2s that I use on tour regularly, sometime last year I had to replace a unit because half of it's red cells stopped working (intermittently at first, then all the time). In the last month another one started doing it intermittently and now a third has started. I've opened them up and circuit board wise everything looks stuck on pretty firmly (although I admit electronics isn't my strong point). Anyone got any ideas why half the red cells would stop working on three separate units?

 

Cheers,

Tom

[timsabre]

The LED emitters will be in a series string so if one of the LEDs fails it will take out all 6 of that colour in the circuit (it's usually 6).

Often this fault is because the LEDs are not soldered down properly. Sometimes one of the LED dies actually fails. You can find the faulty one by bridging across the red pins of each LED in turn with a bit of wire, the rest will light up when you find the fault.

To resolder you will need to use a high powered soldering iron with a big chunky bit as the metal PCB will absorb a lot of heat.

 

[StopWatchingTV]

The LED emitters will be in a series string so if one of the LEDs fails it will take out all 6 of that colour in the circuit (it's usually 6).

Often this fault is because the LEDs are not soldered down properly. Sometimes one of the LED dies actually fails. You can find the faulty one by bridging across the red pins of each LED in turn with a bit of wire, the rest will light up when you find the fault.

To resolder you will need to use a high powered soldering iron with a big chunky bit as the metal PCB will absorb a lot of heat.

 

 

Amazing, thanks for your quick reply. I'll open the spare (broken) one up first and have a go with that one, just incase I end up doing more harm than good! Do you think it's just coincidence that it's the red cells going in each unit or maybe there's an inherent flaw with that section of circuitry?

[alistermorton]

Try putting it on full red then applying some pressure to the individual emiiters and the board from the other side. You may find one has a bad connection, as Tim says, probably a dry joint.

[timsabre]

Do you think it's just coincidence that it's the red cells going in each unit or maybe there's an inherent flaw with that section of circuitry?

Probably just cheap LED emitters... or bad soldering in the chinese factory.

Alister is right that a bit of poking (end of a bic pen or something) may reveal the location of the problem.

 

[sunray]

Do you think it's just coincidence that it's the red cells going in each unit or maybe there's an inherent flaw with that section of circuitry?

I don't think it's coincidence. Red LED's usually run at a lower voltage and current than the others. I don't know these particular fittings but the types I have repaired usually have 3 or 6 LEDS in series with a resistor on a nominal 12 or 24V and so far I've found red's are running pretty much on their limits whereas the others, particularly blue, are well below the max.

[timsabre]

Red is lower voltage but usually driven at the same current, you're right though that the absolute max current rating for red is often lower than the max for green and blue. Also the fixtures under discussion use a constant current driver, not resistors.