Replacing the transformer in a TV to convert its input voltage (120V to 220V)? - Page 1
Forum section: electronics / repair

author: Toxotai
author_rank: Newbie
timestamp: February 21, 2022, 02:15:45 am
content: Hi everyone,Newbie here, very limited electronics repair experience. Mostly just done mobile phone repairs that don't involve board-level repair.So, basically I moved from the US to Spain some years ago, and since I was a bit short on cash and had some space in my bags, I miraculously shoved a 32" TV I'd kept in storage into luggage, threw it into a plane, and managed to get it to work after I got back to Madrid. However, I've had to plug it into a cheap voltage converter that I bought off Amazon a couple of years ago. It's been buzzing to high hell lately, and besides the annoyance of having to pay more money for a better inverter to get it to work, it also has zero resale value here in its current state.So, basically, would it be possible to convert a non-dual-voltage TV's 120V PCB into a 220V by replacing the transformer inside? Would I also have to replace other components too, or does the power feed directly into the transformer, which then spits out 12V for all other operations on the board? For reference, it's a VIZIO D32h-C0, and I've attached a picture of what I believe is the same board. I haven't wanted to open up my TV to take a photo of it myself just yet, until I at least get confirmation from you guys that I'm not a moron for even trying.Also, please don't tell me to buy a new TV. I'm going to buy a new TV. I'd like to just try this as a fun project.Thanks.

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 21, 2022, 02:27:38 am
content: Most practical would be to find out what voltages the internal power supply outputs and substitute an external power supply. If you're lucky, you'll be able to use a PC power supply for that.

author: bob91343
author_rank: Super Contributor
timestamp: February 21, 2022, 02:43:12 am
content: Chances are it's a switching power supply and the best approach might be to get a line operated transformer designed for conversion. They aren't cheap. Or write the manufacturer and find out what they changed inside to make it work in different world markets.

author: coromonadalix
author_rank: Super Contributor
timestamp: February 21, 2022, 02:51:11 am
content: If you dont have a schematic, the simplest way is an standard transformer 240v - 220v to 110vacthey should not be expensive, since a tv is not consuming lot of current, do not use some line voltage converter gimmicks

author: Kim Christensen
author_rank: Super Contributor
timestamp: February 21, 2022, 05:25:03 am
content: Quote from: Toxotai on February 21, 2022, 02:15:45 amIt might possible to fix/silence the buzzing converter instead of trying to convert the TV to 220V. Maybe post some info about that as well?

author: inse
author_rank: Super Contributor
timestamp: February 21, 2022, 06:57:45 am
content: Funnily enough I'm into a similar topic.I have an old Commodore CRT monitor 120V version which is running on a transformer right now.A previous owner has tried connecting it to 230 directly with limited, very limited success.After replacing the DC link capacitor (with a 450V type already), the SMPS is running happily again.I examined the schematics for both versions and they are identical except for the capacitor.I have not yet been able to find out whether the transformer has different specs and the circuit is limited within its regulation or they only made two versions to save a few cents on the capacitor.I raised the voltage up to 180V with my variac without immediate issues, but did not dare going further.For the time being, I will operate it with the transformer, not to destroy the SMPS hybrid.Why don't you try to silence the transformer?Maybe also check whether the DCLINK cap might have lost capacitance causing higher ripple on the AC line thus generating noise in the transformer.

author: samnmax
author_rank: Regular Contributor
timestamp: February 21, 2022, 07:56:07 am
content: This is a switching power supply, the yellow transformer is not directly converting 230V into 12V.As inse said, it COULD be a matter of just replacing the big capacitor (the one on the left marked NFA 200V 120uF) with a 400V or 450V rated one.HOWEVER, there are some things that should be checked before attempting it:- The voltage rating of the bridge rectifier (component BD801?, the flat rectangle besides the capacitor with a + and - symbols)- The voltage rating of the switching transistor (Q501? the one on the left of the transformer)- The switching controller IC (on the bottom of the board), the chip or the components could also be specified only for 120V.- Other things I may forget.It is a risky modification, which could cause some fireworks if it goes wrong. Or worse, unattended fire. If you can get a quality 230V->120V transformer, or fix the buzzing on the one you have, that would be a safer solution. Maybe try tightening the bolts on the transformer or preventing the case from vibrating?

author: abdulbadii
author_rank: Frequent Contributor
timestamp: February 21, 2022, 09:00:17 am
content: "Voltage converter that I bought off Amazon a couple of years ago. It's been buzzing..."just identify or get schematic or open cover to take shot and upload here to fix it