posty07

Hi all,

Trying to identify the attached damper part - I see them on a few different scanners but have never managed to find any replacements other than direct from the manufacturer. 

Anyone know what these are called/where to buy in the UK?

TIA

Adam

Hi all,

Probably unlikely.. but I'm trying to source an entire top half of an inno scan LED. 

Does anyone have maybe a broken one lying around that I could purchase? 

Thanks!

18 hours ago, DrV said:

You're welcome. Out of interest, what is the supply voltage they use on that fixture?

For the LED? It's 5v 18a

The main board uses 12v 8a

Hi All,

I've bought replacement barrel mirror strips for a barrel lighting effect, but they don't come pre-assembled in any way. 

They will be rolled around the metal disc at one end but they are just held by tape or glue at the other end.. 

My question is, does anyone have any experience with this and what did you use as the "tape/glue"?

The Chauvet rep I spoke to suggested carpet tape but I've no experience and don't fancy buying it if it's not going to work

Cheers!

On 11/7/2022 at 10:22 PM, DrV said:

Ignore the In+ and In- pins - you can't glean any information from their voltages as they are current inputs rather than voltage inputs. What you are seeing is simply the LM358s doing their job - their outputs will vary in order to get the correct current through the sense resistors. The difference between the drive voltages is to adjust for slight differences in component values. These include, but are not restricted to, the value of the sense resistors, the gains of the MOSFETs, the slight temperature difference between the MOSFETs, the Vgsth of the MOSFETS and whether there is an R in the month! If you were to squirt some freezer spray on one of the MOSFETs while monitoring the output voltage of its associated LM358 you'd probably see the voltage swing quite markedly while the LED current remained constant.

So, in summary - don't panic! It's working correctly!

Dave

Ah that makes perfect sense, thanks! In that case they're all working as they should after mosfet (and thermal pad) replacement surgery.

Thanks again for your help on this!

On 11/2/2022 at 10:12 PM, DrV said:

Actually you could do a lot with a decent voltmeter - when the led is full on you should at least be able to measure the voltage across the current sense resistors and the reference voltage. Maybe compare with a working PCB.

Hi @DrV

I've now replaced with the new exact replacements and it's working perfectly. Both sets of current sense resistors are getting ~100mv.

One thing I'm a little concerned about is the MOSFET driving voltage is different for each one and my thought is maybe the LM358 is damaged and not outputting the full voltage.. is this likely?

So measuring the LM358 we have:

Vcc: ~5v

In1+: ~0.9mv

In1-: ~0.9mv

Out1: ~4.8v

In2+: ~0.9mv

In2-: ~0.9mv

Out2: ~3.6v

Am I wrong to assume there should be a much lower voltage drop? 

So, I was doing a bit more measuring now I'm familiar with the proper operation of those 2 chips and turns out even the "working" one had a problem.

Dry joint on the drain of one of the MOSFETs was causing it to dim slightly too because the current sense resisters weren't getting anything.

Fixed that and I can now see that those replacement MOSFETs are just not letting through enough current at all. I'll update once the new ones are in!

Thanks for all your help so far

18 hours ago, DrV said:

Actually you could do a lot with a decent voltmeter - when the led is full on you should at least be able to measure the voltage across the current sense resistors and the reference voltage. Maybe compare with a working PCB.

Yep that worked perfectly, the dim one is only getting 23.5mv whereas a good one is showing 100mv.

However the dimmer one is the one that I've replaced the MOSFETs with the wrong or at least different ones. Is this likely the issue?

I'd guess this will happen if the gate doesn't get enough voltage to turn on enough?

13 minutes ago, DrV said:

Actually when the 393 is on the voltage from the current sense resistors will be zero (because no current is flowing) so the 358 output will go high but it still won't be able to turn on the MOSFET because the 393 is preventing it. The 393 "overrides" the 358.

When the 393 is off the 358 is allowed to function normally and sets the current as required.

I finally get it! 

Thank you for your excellent explanation, that's genuinely really helped me.

So to test this I'm going to need a scope aren't I..?

AHH I think I get it. 

So when the 393 is 'off' it is floating but when on, the output shorts to ground..? Because of this, the current sense should be low, so the 358 turns off? 

Have I understood that correctly?

So if the 393 is outputting high, then the 358 also outputs a voltage to drive the MOSFET?

I really need to do some more research on these circuits as they're confusing me slightly!

1 hour ago, alistermorton said:

Perhaps there's a ramp generator and a comparator to convert the analogue voltage to PWM?

There is a Shunt regulator.. not sure if that's the same thing - but no ramp generator. As far as I can tell this isn't using pwm to dim the LED.

Seems to be current limiting instead, perhaps to ensure flicker free? I'm no expert so I'm not exactly sure but that's how I've understood the circuit.

2 hours ago, indyld said:

Total guess but perhaps one is in a voltage comparator circuit that the trim pot is also part of.

Yes I think it is, I've checked the pot and it's working well.

The 3 pin connector comes from a control board which gives it a 5v power, ground and a control PIN which seems to change voltage to control the brightness - which I'm guessing is what the comparator circuit is for

6 hours ago, indyld said:

Look up the differences between constant current and constant voltage drivers.

What are the numbers on the two SOIC8s?

PS. Use lots of added 60/40, flux (and in some cases low melt solder) and some decent wick to make a better removal job. Having said that, a low quality iron will also often mess pads up. Or a poorly sized tip. 

Thanks I will - to be fair most of that burn was there already as these appear to get very very hot..

The IC on the right is an LM393 and left is LM358. Both double op amps which appear to be working. Though I'm having trouble working out how the output is calculated using the 2 inputs.

A few photos of the board. I've swapped the MOSFETs on this one for a similar spec but I've since realised that their fully 'on' voltage is a little higher. 

To me this circuit seems to not use pwm to dim the LED and actually seems to use current limiting using the MOSFETs.. of course I could be very wrong.

I'm waiting on exact replacements so hopefully they will do the trick as the led is now brighter, but not completely full, with these replacements.

P.S. ignore the missing pad underneath.. too much heat applied - it doesn't connect to anything as it's the pad on the top that connects to its trace

I mean they look great but unfortunately it's just a hobby so I can't justify it 😢

Would one of these little things be any good for basic troubleshooting?

https://www.ebay.co.uk/itm/385040468593?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=-4xkiftwsz6&sssrc=2349624&ssuid=5Ff1NvmRTVm&var=&widget_ver=artemis&media=COPY

30 minutes ago, Brian said:

If you are serious about wanting to fix things then it's time to buy a scope.

£100 on ebay will get you something worth owning.

I've been looking actually and really want one but I don't know what specs or models are going to be useful!

Any recommendations?

16 hours ago, indyld said:

Post decent pics of the board. Perhaps only half the frequency is resulting in half the on time. Either MOSFET not opening or gate driver not driving. 

 

Might be able to diagnose using a camera and a working unit to compare flicker. 

Ok I'll get some pics later today - I hadn't thought of that as a troubleshooting step, will give it a go!

I think they might be flicker free but it's worth a try 

Hi all,

I'm currently purchasing broken LED lighting to repair - not massively expensive stuff, more like DJ lighting, par cans or scanners/barrels with faults. 

Does anyone have anything they could offer?

Cheers!

Hi all,

I'm looking at a few 300 LED Barrels which have very low output on the LED.

The LED itself is fine as I've swapped the driver from a working one and it comes back to life. 

Whatever the problem is, it seems to be common to these as they're all acting the same.

I've done a fair bit of testing between the working and broken one and most voltages, resistances etc seem to be very similar if not exactly the same. These boards use 2 MOSFETs from the -ve pin of the led to ground. Each shares half the load. 

My question is.. is it likely that the MOSFETs are bad? Just normally I'd expect a MOSFET to fail short circuit.

Cheers

Adam

Hi both, thanks for the advice!

I'd agree it's probably getting too hot but what I find odd is that the thermocouple reads at 300 degrees c (by probing with a mm) when it switches off then goes back on at around 260.. does that sound a bit hot? Do you know if thermocouples are pretty universal..? Reckon this might work? https://uk.rs-online.com/web/p/thermocouples/6212170/

Very possibly could be a bad air pump, it's a few years old and the pump runs almost constantly, reckon it's worth replacing? What pumps do your machines use?

Hi All,

Recently purchased a hurricane 1dx listed as spares or repair due to not doing anything. Turns out the overheating sensor had just clicked - annoyingly it's a manual reset type..

So after resetting, it started heating up and the pump/air pump kicks in as it should and it does start producing a nice haze. However it's spitting a lot whether on low med or high setting

Things I've tried/tested

- made sure the main pump works fine, it does

- checked air pump

- checked the thermocouple temp measured with a multimeter

- cleaned with a mix of 50/50 deionised and distilled vinegar for around 30 mins.

The overheating sensor does kick in again if it's left plugged in without pumping fluid for around 30 mins

I'm using actual Chauvet haze fluid so I'm pretty certain it's not that..

Any ideas?

Thanks!

Hi all,

Hoping to source a mounting bracket for a Chauvet LED 200.. anybody got one or even a unit for sale for parts?

Many thanks!

Hi all,

Hoping to source a mounting bracket for a Chauvet LED 200.. anybody got one or even a unit for sale for parts?