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Reliance cable hound transmitter burned component question

 
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lestro



Joined: 02 Mar 2015
Posts: 1
Location: USA

PostPosted: Tue Mar 03, 2015 3:32 pm    Post subject: Reliance cable hound transmitter burned component question Reply with quote

I put batteries in a reliance telcom cable hound 71-620-00-D015 that had been stored for about 20 years and smoked a componet on the transmitter. I can't find a schematic for it anywhere, but I suspect the fried part is a tantalum capacitor of unknown value located in the picture where the 2 pins are sticking up which has full 12vacross them. Whatever it was it had a green moulded base similar to the blue parts shown. the blue one in upper left has writing on it of 6.8 35v +, the left one is red pink green(no other markings) and upper center is blue gray green. Is anyone familiar with these components or circuit board? thanks in advance [img]http://s1377.photobucket.com/user/jltrone/library/?sort=3&page=1[/img]
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torbjorn



Joined: 07 Jun 2007
Posts: 371
Location: Sweden

PostPosted: Thu Apr 23, 2015 4:08 pm    Post subject: Reply with quote

Old tantalum capacitors do often burn when they are suddenly subjected to full voltage after many years on the shelf. And some unreliable brands may burn at any time. However such faults are very seldom on modern tantalums (manufactured in the mid 90's or later).

It seems to be a fairly simple circuit board, so it should be an easy task to reverse engineer it and make a schematic. Then you can probably figure out the purpose of the burned capacitor and a suitable value for it.

Probably a tantalum or electrolytic of 10 uF 35 V or so will work well there. Just remember to check the polarity at the pins so you can connect it with correct polarity.
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sohaibing001



Joined: 31 May 2015
Posts: 1

PostPosted: Sun May 31, 2015 8:40 pm    Post subject: Reply with quote

Hi lestro,
When it comes to simple circuits like this one capacitors generally don’t require very precise value to be calculated while being replace but in your case I think it does. You’ll have to make a rough schematic of the circuit to find out the purpose of this capacitor. If it is being used for noise reduction in a digital line, just replace it with 10uF or 100uF. If it being used as a filter with ay resistor, you’ll need some engineering skills to calculate the required values.
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viya0414



Joined: 02 Sep 2017
Posts: 1

PostPosted: Sat Sep 02, 2017 2:21 am    Post subject: Reply with quote

You’ll have to make a rough schematic of the circuit to find out the purpose of this capacitor. If it is being used for noise reduction in a digital line, just replace it with 10uF or 100uF.



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