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What is this black item

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City fan

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img004 modified modified.jpg
I can't find what the black part in picture is with number 8508 and 2016.

It's part of motor control circuit.

Could someone please tell me what this item is.
 

I wish I could test it, It's an old board and some components have been removed, this part is one of them and i've lost it.
Thought I'd bring thing back to life. Luckily i've photo'd all parts.
Unfortunately I can't find this part listed anywhere.
Left end attached to collector of a TIP32A, right attached to battery negative.
 

Diodes without an anode ring are usually bipolar TVS (transient voltage supressor power zener) diodes. SIDAC would be another possibility for a bipolar device.
 
Thanks for your help, I'll see if i can find something on the net using your sugestions.

Look tomorrow and let you know.
 

Thanks for your reply, I'm sure you're correct with your suggestions, on reading up on what TVS diode does.

Unforunately I can't seem to find anything listed with those part numbers.

Must look harder through my untidy workshop to try and find origional , or give up trying to repair.
 

City fan said:
Thanks for your reply, I'm sure you're correct with your suggestions, on reading up on what TVS diode does.

Unforunately I can't seem to find anything listed with those part numbers.

Must look harder through my untidy workshop to try and find origional , or give up trying to repair.
Click to expand...

If You make connections (schema) from existing PCB maybe is possible to guess of part type and value.

What is written on case of right TO92 part ?
 

Hi tpetar,
Ive made a rough shematic of the board, this unit is attached at left end to a transistor TIP32A collecter terminal and the right is connected to the negative track.
The TO92 shown is a BC548B its not connected directly.
I've started to make a proper circuit diagram, will post when completed.
 

img123.jpg img122.jpg

Sorry taken a week to complete this, but did in wrong progamme and couln't copy.
Hope this makes sense and you can help me further with maybe an alternative i could use in place of origional i've marked.
Thank you in advance.

First image not good tried again
 
Last edited:

Your diagram and the symbol shows it as Zener Diode. Some extended search on NET I found some references as 12 volts 1 watt zener but could not get the datasheet.
 
Hi thanhs for your reply, just realised made mistake on first diagram at the top, don't suppose it make much difference to your diagnosis but i've attached revised plan.img124.jpg
 

I just added to diagram as a zener diode. there are no markings to identify A nor K,
All I have is it's all black with markings of 8508 and 2016
 

OK, if the diagram belongs to the same PCB then it is connected as I said, cathode to the Transistor Collector if you want to check it with a DMM or want to replace. Is there any thing written on the PCB to give a hint for this component?. Can you check it with DMM for it conducting behavior?
 
As previously mentioned, a diode package without polarity marking usually refers to a bipolar TVS diode or other bipolar device, e.g. a diac. A bipolar TVS diode is essentially comprised of two back-to-back connected z-diodes, and can be used as zener diode replacement. It may be the case, that a bipolar TVS diode has been used instead of an unipolar one.

You can't identify it by it's diode forward voltage, but you should check the zener voltage anyway, if you are unclear about the correct diode type.
 
But as per diagram the symbol showing a zener whereas or me the TVS has the following symbol.
TVS.jpg
 
I just drew the item as a zener as not sure what symble to use.
No markings on board to give any clues.
Unable to test old unit as it's been misplaced.
Is it an item thats absolutely necessary, could it be ommited?
Is triac, diac, and sidac used for AC current only?
Maybe best thing to do is reassemble board and try different units in this space.
 

But as per diagram the symbol showing a zener.
Click to expand...
So what? The diagram hasn't been supplied by the manufacturer. It's reverse engineered, I think.

The actual problem is to find out a suitable zener voltage, assuming it's a zener (or a bipolar zener/TVS used in it's place).

I'm under the impresion, that I have explained clearly enough, that a bipolar TVS diode could be used in place of a regular zener diode for some reasons, e.g. available stock.
 
So what? The diagram hasn't been supplied by the manufacturer. It's reverse engineered, I think.
Click to expand...
I was not sure about the diagram whether self drawn or been with the PCB, thats why I assisted. Yes a TVS is a reverse connected two zeners. Yes it can be a TVS and (now after clarification) it is a Bipolar TVS. If this is not connected for the sake of testing it is ok, as it is for safety and connected across the motor.
 
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