GHD 4.0B 'D2' Diode replacement

Andrew
Posts: 5
Joined: 19 Jun 2015, 08:33

GHD 4.0B 'D2' Diode replacement

Postby Andrew » 19 Jun 2015, 08:37

Hi Gary

GHD 4.0B, on the non switch pcb side, there's a diode labelled 'D2', right next to the pair of 'R7 resistors'.
Please can you let me have the value of that diode?

Regards
Tony

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

Re: GHD 4.0B 'D2' Diode replacement

Postby gary » 19 Jun 2015, 09:17

Hi Tony,

I've never seen it fail so do not know what replacement part would be compatible.

What is wrong with the irons that leads you to want to replace it?

Gary

Andrew
Posts: 5
Joined: 19 Jun 2015, 08:33

Re: GHD 4.0B 'D2' Diode replacement

Postby Andrew » 19 Jun 2015, 09:33

Turns out that I didn't get an ohm reading using a multimeter to test the diode, and removed it from the board, but it's so tiny, I fear I might not have tested it properly, and now that it's off the board, I figure I might as well replace it with a generic, or equivalent part. And, as luck would have it, the R8, 100 ohm melf resistor needed to be replaced as well.

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

Re: GHD 4.0B 'D2' Diode replacement

Postby gary » 19 Jun 2015, 09:56

Hi Andrew,

You won't get a resistance measurement across a diode. You need to do a diode voltage drop test. Chances are it is fine and the only issue is the R8 resistor (as that fails all the time on this model).

Gary

Andrew
Posts: 5
Joined: 19 Jun 2015, 08:33

Re: GHD 4.0B 'D2' Diode replacement

Postby Andrew » 19 Jun 2015, 10:08

Agreed, thanks so much for your help, Gary... Any idea what the voltage across that diode might be? In the end, because I foolishly removed it from the board, I still need to have it replaced.

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

Re: GHD 4.0B 'D2' Diode replacement

Postby gary » 19 Jun 2015, 10:20

Humm.... not sure!

There is a circuit diagram here that might help - http://www.ghd-repair.co.uk/images/GHD4 ... ircuit.pdf

Looks like it is a low voltage diode on the reset pin.

Andrew
Posts: 5
Joined: 19 Jun 2015, 08:33

Re: GHD 4.0B 'D2' Diode replacement

Postby Andrew » 19 Jun 2015, 10:23

Ah, excellent, much appreciated, thanks...

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

Re: GHD 4.0B 'D2' Diode replacement

Postby Webinfusion » 19 Jun 2015, 20:04

Hi,
D2 is the interupt line for the pic chip and is proberly a zener used to produce a square wave at mains frequency at 3.3 to 4.5 volts, if the pic bleeped before removing then put it back in as it was working, if not rob one from a fake board.

Cheers
Kev

Andrew
Posts: 5
Joined: 19 Jun 2015, 08:33

Re: GHD 4.0B 'D2' Diode replacement

Postby Andrew » 22 Jun 2015, 08:00

Hi Kev

Thanks so much for the advise, I managed to get the GHD up and running, soldered in a 2.7v diode and replaced the R8 resistor...
All is well in the world again.

Regards
Andrew


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