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Inverter Modifications

Technician Tonny

Aug 31, 2015
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HI.... Is it posible to modify a dc inverter circuits which are inbuilt in crt television sets,
The inverter output is soldered directly to the crt power filter capacitor,
what if i remove the brigde, will it output stable 220VAC?!
 

davenn

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Sep 5, 2009
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HI.... Is it posible to modify a dc inverter circuits which are inbuilt in crt television sets,
The inverter output is soldered directly to the crt power filter capacitor,
what if i remove the brigde, will it output stable 220VAC?!

hi

you would have to tell us a lot more about the particular PSU
a circuit diagram is going to be essential before any good suggestions could be given
 

Technician Tonny

Aug 31, 2015
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Davenn i tried googleling for the schematic but i found no matching circuit according to the one i have

The inverter board uses two ic's ne555 and sg3524n, smp transformer and two fets....

I tested its output with a d m meter and found 300 vdc, and at the transformer's output b4 the brigde, the meter shows high voltage....

Such inverter circuits are found in CRT TV's which operate with both AC AND DC voltage

I'm working on its schematic, i will provide it wen its done
 

Aplicant

Nov 16, 2016
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If you remove inverter output bridge diodes , inverter outputs
310 vac 50 khz squarewave
It never outputs 220vac 50 hz
 

duke37

Jan 9, 2011
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If it is a ferrite cored transformer, it will never be able to run at 50Hz.

To get 50Hz you will need an iron cored tranformer and the SG362 modifying to generate the correct drive. frequency.
This circuit produces square waves. The output can be filtered to give an approximate sine wave or a class D drive to generate a sine wave
 

Technician Tonny

Aug 31, 2015
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duke37
I have iron cored transformer's from old ups, hope it can work!

and how can I modify the SG to change the frequency
 

Audioguru

Sep 24, 2016
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The datasheet of the 555 and the SG tells you all about them.
Your modified inverter output voltage will be too high when the load is light and will be too low when the load is heavy because it is missing voltage regulation.

The heatsinks on the Mosfets are small so the Mosfets will melt if the inverter power is more than not much power.
 

Aplicant

Nov 16, 2016
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If you want to take 220ac from your inverter in crt,you have to add this circuit. It converts 310vdc to 220ac
Apply this
78_1319388238.jpg

You have 300vdc so you dont need ic1 and components around ic1
54_1319388238.jpg
 

Technician Tonny

Aug 31, 2015
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Audioguru
let me check the datasheets
Thanks


Duke 37
I change the ct and the transformer ..ok let me do that now

i don't use the ups because it used to drain the battery so quickly, it works for only 2 hours


Aplicant
I also remove R8 and D4 its like a feedback or comunication between the two ics!

Thank you all for your assistance i really appreciate
 

Technician Tonny

Aug 31, 2015
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Why do you think that you can make a more efficient power convertor than a commercial one?
because ups a multpurpos... they charge, they work as automatic voltage regulator, power backup for computer sets.
i think they where not designed to stay on for so long as inverters
 

Technician Tonny

Aug 31, 2015
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Your modified inverter output voltage will be too high when the load is light and will be too low when the load is heavy because it is missing voltage regulation.

your right now the inverter outputs
__ 240vac without any load
__ 130 vac when i connect a 100 wat bulb , and the 240 drops to 40 vac when i connect a crt tv,
I tried another transformer and its output is 280 vac and drops to 180 when i connect a 100 watt bulb
but am still wondering why it just increases the voltage to 300 vac when i connect a crt tv
How to add the missing part of regulation,

The heatsinks on the Mosfets are small so the Mosfets will melt if the inverter power is more than not much power

The mosfets a still cool
 
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