Turning on problem (possibly the optocoupler?)

emmarann
Posts: 5
Joined: 06 Jul 2014, 09:54

Turning on problem (possibly the optocoupler?)

Postby emmarann » 06 Jul 2014, 10:12

Hi there,

I'm determined to get to the bottom of the fault I have. The power switch has been problematic for a while but after taking it apart and cleaning it it is now fixed so I'm getting the correct switching voltages at the terminals. The next stage of the problem is getting an output from the zero crossing optocoupler. When it's all turned on there is no output from mt1 and mt2. If I momentarily touch the anode and cathode together (pins 1 and 2) it springs to life and works perfectly, getting up to temperature and flashing once it gets there. What I'm not sure about is do you think it's a problem with the MC3041 or is this likely to be a problem from elsewhere on the board that's not giving the correct starting pulse to the optocoupler?

If you think it's the optocoupler I might try and replace it and see if it fixes it, otherwise I guess it might be a whole new pcb.

Note the thermal fuse seems fine and the heater plates are fine. As it goes up to temperature fine once it has started i don't think these need replacing.

Any advice would be greatly appreciated!

gary
Site Admin
Posts: 1032
Joined: 26 Jan 2008, 00:44

Re: Turning on problem (possibly the optocoupler?)

Postby gary » 06 Jul 2014, 22:14

Hi,

Just to clarify the basics.... you measure 80 ohms on the heater when they are both connected to the PCB and 160ohms when they are disconnected?

The PCB very very rarely fails, so I always need to check the basics first!

Gary

emmarann
Posts: 5
Joined: 06 Jul 2014, 09:54

Re: Turning on problem (possibly the optocoupler?)

Postby emmarann » 06 Jul 2014, 22:41

Thanks for replying, I'll double check the resistances tomorrow and let you know, I hadn't tried disconnecting each heater- they are both heating up fine though (once it starts up) so do I really need to desolder them just to check?

gary
Site Admin
Posts: 1032
Joined: 26 Jan 2008, 00:44

Re: Turning on problem (possibly the optocoupler?)

Postby gary » 06 Jul 2014, 22:47

Hi,

Desolder? If they are 3.1B's then the heaters will be screwed to the PCB. If they are definitely soldered then that means they are fake 3.1Bs.

Genuine 3.1bs look like this inside:
http://www.ghd-repair.co.uk/3.1B.html

The only irons that have soldered heater elements are the really old "pre mk3s":
http://www.ghd-repair.co.uk/pre3.html

Gary

emmarann
Posts: 5
Joined: 06 Jul 2014, 09:54

Re: Turning on problem (possibly the optocoupler?)

Postby emmarann » 07 Jul 2014, 06:38

Hi,

They are genuine and resistered with ghd but they were bought as reconditioned units which may explain the slight internal difference. They have lasted 7 years so they've done well until now! I'm now wondering if they originally replaced the whole pcb.

The heaters are soldered to each end of the board, putting the ohmmeter across I get 60 ohms on one and 55ohms on the other, not sure if that means they've dropped a bit from what they were new?

Here's a photo:
https://www.dropbox.com/s/lzemjuy7j5eim ... 3%2053.jpg

Thanks for replying.
Emma

Webinfusion
Posts: 134
Joined: 20 Jan 2012, 02:13

Re: Turning on problem (possibly the optocoupler?)

Postby Webinfusion » 07 Jul 2014, 12:24

Hi Emma,
From the picture the PCB is fake, the serial number is also listed as a known fake.

Many thanks
Kevin

emmarann
Posts: 5
Joined: 06 Jul 2014, 09:54

Re: Turning on problem (possibly the optocoupler?)

Postby emmarann » 07 Jul 2014, 12:41

Well I have to say it's been a reliable fake up until now... Oh well, maybe it's time for some brand new ones :)

Thanks for looking at it.

Webinfusion
Posts: 134
Joined: 20 Jan 2012, 02:13

Re: Turning on problem (possibly the optocoupler?)

Postby Webinfusion » 07 Jul 2014, 13:54

Hi,
Hope your still going to repair it since you have got this far, i would imagine the MC3041 is ok and its the starting pulse thats a problem.

P.S some fakes were good, others are dam right dangerous

cheers
kevin

trev260764
Posts: 70
Joined: 07 Oct 2013, 17:35

Re: Turning on problem (possibly the optocoupler?)

Postby trev260764 » 08 Jul 2014, 23:02

I have a few pairs of brand-new MK5's in black/gold for £75 - and GENUINE!! Let me know if you are interested...

Trev

emmarann
Posts: 5
Joined: 06 Jul 2014, 09:54

Re: Turning on problem (possibly the optocoupler?)

Postby emmarann » 09 Jul 2014, 06:27

Thanks but I just bought a new set in the sale. I'm still determined to fix my old ones as spares though...

Thanks.


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