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Replacing The B+ Coil With A Wire?

By Jestine Yong on February 10, 2010

I believe CRT Monitor repairers came across B+ coil in the circuit. The function of the B+ circuit (boost circuit) is to boost the Dc voltage from the SMPS so that it can be channeled it to the flyback transformer primary winding. The B+ voltage is required to support different resolution in the Monitor. That means the B+ voltage will vary if the display resolution change. If the B+ coil burnt the only way is to replace it with a new coil or you rewind it on your own. The question is can we replace the Burnt B+ coil with a single wire?

The answer is No because the function between a coil and a wire is different. The function of the B+ coil is to store current and the wire is to act as a path for the Dc voltage to flow through. In other words, without B+ coil there will be no current be transferred to the B+ capacitor in the B+ circuit thus the voltage can’t be boosted. If the B+ voltage is not boosted then the flyback primary winding would not get what it want (flyback needs a higher DC voltage) thus the high voltage generated would be low-may in the range from 12 to 15 Kvdc only.

Because of this situation, the display will become small vertically (may be 6 to 8 inches wide) and in some cases the display curve inwards (squeezed in the right and left side). Hope that in the future, if any B+ coil burn, please do not put a wire to replace it.

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10 Comments

Ordan Graham

February 18, 2010 at 10:53 am

HI Jsetine, Great site. I have not read your download as yet as I need more memory to get adobe reader installed. You are a real pro. I have learnt so much from your site.

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admin

February 19, 2010 at 11:28 am

HI Ordan,

Thanks!

Jestine

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SREEDHAR KORUPOLU

February 21, 2010 at 9:54 am

HI, MR JUSTINE , U AND UR WEBSITE ARE FANTASTIC AND VERY MUCH HELPFUL, THANK U, WHERE CAN I GET UR WORTHFUL BOOKS IN INDIA KINDLY SENT ME ADDRESS,, THANK U ONCE AGAIN

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admin

February 22, 2010 at 9:23 am

HI Shreedar,

Since my books are ebooks thus you will not find it from any bookstore. You have to buy it from the website using credit card or you can email me at jestineyong(at)electronicrepairguide.com for alternative payment

Jestine

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Ayaz Haider

March 11, 2010 at 1:58 am

HI Jestine,
first i appreciate your Great site,
I have Dell E773c CRT 17" Monitor,
The problem is that the monitor power supply is ok and power LED is on and yesterday it show a blured Circle in center of screen but now there is no display..
I believe it makes EHT Volts.
Can you please advice or let me know where i get the scematic diagram or service manual

Regrads,

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admin

March 11, 2010 at 8:24 am

HI Ayaz,

Sorry info about the schematic. Have you try this link:

https://www.jestineyong.com/?cat=59

Jestine

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Galib

February 17, 2012 at 4:59 pm

Hi Jestine,
I have made by china 17" CRT Monitor named "ORANGE" . It's circuit same as 17" Flat Samsung Monitor . This Monitor's Problem is - It's Brightness is very Low . I changed it's Flyback Transformer but no result . Then I changed it's Base Circuit also but the same result .

Is it the problem of B+ Coil of this monitor ? Can you give me some advice to get rid of this problem .....

Thanks
Galib

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admin

February 17, 2012 at 10:20 pm

HI Galib,

If the heater voltage, g2 and g1 voltage are normal then the picture tube already weak and need to be replaced.

Jestine

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xerxes

December 12, 2018 at 11:00 pm

I have a question about the word "B+ coil" where it comes from

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- Jestine Yong
  
  December 13, 2018 at 4:35 pm
  
  HI Xerxes,
  
  The coil/inductor is along the B+ circuit (in-series) thus it is a B+ coil.
  
  Jestine
  
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