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#216516 - 12/27/15 07:11 PM Need help identifying diode
Potseal Online   content
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Registered: 02/23/13
Posts: 188
Loc: Saskatchewan
I looked all over the Internet and couldn't find anything. Normally it's a fairly straight forward search using the markings on the diode. This particular diode came out of a Dukane nurse call patient station:



Looks like "TZB 6.8A". That "B" might even be an "E". I tried every variation. On the opposite side is an "SI" which I assume stands for Silicon. Any help would be appreciated.


Edited by Potseal (12/27/15 07:13 PM)
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#216517 - 12/27/15 07:15 PM Re: Need help identifying diode [Re: Potseal]
Potseal Online   content
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Registered: 02/23/13
Posts: 188
Loc: Saskatchewan
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#216519 - 12/27/15 08:09 PM Re: Need help identifying diode [Re: Potseal]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8530
Loc: SI,New Zealand
This may be of no help to you, potseal, but if you could possibly find a circuit diagram for the device, that should tell you what sort of diode it is.

Also, I think the character you suspect is a B or an E could in fact be the symbol for DC.


Edited by Trumpy (12/27/15 08:11 PM)
Edit Reason: Added second part.
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#216522 - 12/27/15 09:38 PM Re: Need help identifying diode [Re: Potseal]
wa2ise Offline
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Registered: 11/29/02
Posts: 769
Loc: Oradell NJ USA
That might be a capacitor, 6.8uF
The band may indicate which end goes to the negative side of the circuit.

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#216524 - 12/27/15 09:55 PM Re: Need help identifying diode [Re: wa2ise]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8530
Loc: SI,New Zealand
wa2ise,
I was thinking, on reflection, that this could be a 6.8V Zener diode, not your stock standard silicon diode.
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#216528 - 12/27/15 11:17 PM Re: Need help identifying diode [Re: Potseal]
Potseal Online   content
Member

Registered: 02/23/13
Posts: 188
Loc: Saskatchewan
Thanks for the replies. I won't be able to search for a circuit diagram for a few days since I'm currently on holidays. I took another look at the board and the diode in question is identified on the board as "CR 1", "CR2", and "CR3". I believe "CR" stands for control relay. I took a picture as well:



I circled the 3 diodes and I circled the row of capacitors that are directly connected to the Anode of the diodes.

EDIT: I just looked up "CR" and according to one source it stands for "diode".


Edited by Potseal (12/27/15 11:29 PM)
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#216529 - 12/27/15 11:24 PM Re: Need help identifying diode [Re: Potseal]
Potseal Online   content
Member

Registered: 02/23/13
Posts: 188
Loc: Saskatchewan
I had a sacrificial board identical to the one in the above image. It wasn't working properly either. I traced the problem to one of the 3 diodes. I replaced the original diode with one that I had in my spare diode container. I used an FR207. It's described as a "fast recovery" diode. Definitely a shot in the dark but ultimately it eliminated the problem. I'd rather have more information to go on to be certain it holds up in the long run.
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#216530 - 12/27/15 11:31 PM Re: Need help identifying diode [Re: Potseal]
LarryC Offline
Member

Registered: 07/05/04
Posts: 775
Loc: Winchester, NH, US
A couple of questions:

How do you KNOW it is a diode? Was there a reference designator printed on the printed circuit board it came out of? Perhaps a CRxx or Dxx.

Is there a schematic symbol printed on the circuit board? Any polarity markings?

Have you tested the component? Diodes typically fail shorted followed by burning open from excess current. The component in the picture looks undamaged. Did you check it for continuity? Diode voltage drop in both directions? Resistance value?

How did you isolate the fault to that component?

Any idea of the function of that component in the circuit?

==========================================================
EDIT
Do the 9 caps sit across a communication data buss? The diodes and capacitors might be used for electronic interference noise suppression. Or voltage termination


Edited by LarryC (12/27/15 11:39 PM)

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#216532 - 12/28/15 12:20 AM Re: Need help identifying diode [Re: LarryC]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8530
Loc: SI,New Zealand
Can we please get a wider view of the PCB to see where this fits into the whole thing?
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#216533 - 12/28/15 12:23 AM Re: Need help identifying diode [Re: Potseal]
Potseal Online   content
Member

Registered: 02/23/13
Posts: 188
Loc: Saskatchewan
Appreciate the response Larry.
As you can see in the image above the location of the diode in question sits on the circuit board with 2 other identical diodes. CR1, CR2, and CR3 are marked on the PCB at that location. This PCB is directly related to the touchpad of the Dukane patient station for such functions as "call", "staff emergency", etc. The board I repaired and the board I'm trying to repair (in the image above) had similar issues. Both boards when powered had touchpad LED indicator lights lit before the buttons were pushed. These lights could not be cancelled or reset. I traced out the circuit from the malfunctioning signal to various components and eventually arrived at the diodes. The first board I repaired seemed straight forward when one of the diodes didn't test properly using a DMM. The board I'm trying to repair now seems to have the same problem except it's two of the diodes that don't measure correctly. I did several resistance measurements comparing the working board with the board that needs repair. The resistance across the diodes that I suspect is far greater than the others. As well, when I compare the R across the capacitors the ones in the malfunctioning board show "OL" while the ones in the working board show approximately 900 ohms.
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