180 WATT CHINA LED DIMMER ISSUE

[Richard CSL]

I now have 4 moving heads Chinese 180 watt led with no dimmer output.

they look like this. The dimmer board has all the main components ID removed. but looks like picture below.

pwm input measures 5 volts + I cant see a signal with my cheapo Aliexpress oscilliscope, but I have no output, all mosfet devices check ok. I replaced 1ohm resistors on this board as they were open circuit, but I cant identify other vomponents.

any help much appreciated.

 

[alistermorton]

Can you get output manually at all? I have an elumen8 MP75 which is not responding to DMX but works manually - I suspect the (integrated into the control chip) bus receiver has been cattled.

[indyld]

Is this post just the same as the previous one you posted, but never came back to?

[Richard CSL]

No this is a different head altogether. But yes I do also have 2 Chauvet style Q260 spots with a very similar problem

[Richard CSL]

No I have tried an external pwm signal and still no output.

 

[timsabre]

Did the 1R resistors you replaced stay working (have you gone back and measured)

Have you tried powering the LED emitter(s) with a bench power supply?

Usual fault mode is the mosfets fail short circuit which turns the power on full which fries the current sense resistors and sometimes the LED emitter. Are you sure the mosfets are not short circuit. If  the LED has failed then driving pwm into the mosfet will not do anything as there is no load - you need to establish that the LED is still working.

Alternative fault mode is the current sense resistors are specified at too low a power rating and they overheat and eventually fail. However in that situation replacing the resistors would make it work again.

Edited August 5 by timsabre

[Richard CSL]

The 1 ohm resistors feed the processor chip marked 3A 3741   N 2823.

there are no voltages after this chip. so I suspect this is the problem, but I cant identify this chip

 

[indyld]

Analog Devices 3741 power controller?  Can be checked with the circuit using the datatsheet.

Edited August 6 by indyld

[Richard CSL]

chauvet pwm. dimmer short = lamp on

 

 

so

pwm required above is +5V, why the difference.??

I have a pwm dimmer from an old Chauvet Q spot. this works fine, (but I only have the one) However I am finding out not all pwm works the same. If I short the inputs on the Chauvet pwm dimmer the led lights. 

I also bought 2 pwm dimmers from Ali baba and uprated the mosfets, these however require 5v pulsing input to control.

[Richard CSL]

https://es.aliexpress.com/item/1005001836699671.html?spm=a2g0o.order_list.order_list_main.20.2286194dTAgzaZ&gatewayAdapt=glo2esp

so after a lot of searching I have found this product range , which I have ordered a sample, if it works I will order more.

Interesting the different voltages and amperages.