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Old 06-25-2019, 05:07 AM   #1
Hitto
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Default Filtering Capacitors Around Flyback Transformers In CRT Monitors

I have a question about the filtering capacitors to be used around the flyback transformer in CRT Monitors.

I mean the 10-22-33uF capacitors which filter ~160V voltages going to the flyback trafo.

1) Do they have to be low E.S.R.?
The original capacitors are usually general purpose, but I suspect this was for cost cutting more than a requirement.

2) Is geometry and picture stability improved in case of increased capacitance?
I've seen schematics on similar models of some old Sony monitors: identical flyback transformer but capacity increased from 33uF to 47uF in a more costy version.

Last edited by Hitto; 06-25-2019 at 05:09 AM..
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Old 06-25-2019, 08:07 AM   #2
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Default Re: Filtering Capacitors Around Flyback Transformers In CRT Monitors

I have usually replaced these with a good quality 105 capacitor, You don't need low esr. Any good panasonic brand will outlast the tv. There is not that much difference between the 33f and 47f caps. as they are usually +/- 20% tolerance, If they are just for filtering the screen supply voltage it won't make any real difference.
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Old 06-25-2019, 08:26 AM   #3
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Default Re: Filtering Capacitors Around Flyback Transformers In CRT Monitors

the frequency is not high enough to need low esr.
good caps like panasonic NHG will make a difference compared to junk like "forever" and other shit on ebay though.
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Old 06-26-2019, 03:24 AM   #4
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Default Re: Filtering Capacitors Around Flyback Transformers In CRT Monitors

Quote:
Originally Posted by R_J View Post
If they are just for filtering the screen supply voltage it won't make any real difference.
Yes, they are for this exact purpose.

Do you guys know the specifications of 105 Samsung ST capacitors? They measure normal E.S.R. (1.10Ω) but I'm struggling to find a datasheet to find out their maximum applicable current.

I'm currently planning to upgrade the capacitance of each supply line by X1,4 and upgrade a little the horizontal width capacitor. Geometry is currently a bit defective and messing with the trimmers is a no-no.
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Old 06-26-2019, 07:08 AM   #5
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Default Re: Filtering Capacitors Around Flyback Transformers In CRT Monitors

watch out for a non-polarised cap - if you find one you can replace it with polypropylene
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Old 06-26-2019, 02:01 PM   #6
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Default Re: Filtering Capacitors Around Flyback Transformers In CRT Monitors

The original capacitor in the horizontal width, from what I read, handles a lot of current (even 10A).

Is one polypropylene okay for such current or do you suggest me paralleling a pair of them just to avoid a worst case scenario?
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Old 06-26-2019, 06:44 PM   #7
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Default Re: Filtering Capacitors Around Flyback Transformers In CRT Monitors

you can get high current ones - download some datasheets.
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