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Anyone used the flyback while still connected to the original TV PCB?

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Steve Hobley

Thu Nov 04 2010, 03:38PM

Registered Member #1731 Joined: Thu Oct 02 2008, 02:22PM
Location: Indiana
Posts: 52

I bought a $10 RCA color TV from Goodwill yesterday and noticed that the internal PCB contains a lot of the stuff I need to make a lifter PSU.

It occured to me that the transformer/rectifier/cap was all probably wired up ready to go, and there was a nice large transistor with heatsink connected just next to the flyback.

Has anyone been successful in just cutting out the PCB sections intact and hooking them up? I was thinking about tracing the paths and then just drilling through any that I no longer required. I suspect I need to add a 555 timer to switch the transistor, but apart from that it looks like I have what I need.

Thoughts?

pauleddy

Thu Nov 04 2010, 04:08PM

Registered Member #2909 Joined: Wed Jun 09 2010, 12:31AM
Location: fort belvoir, Va USA ( south of DC)
Posts: 145

i use my flyback straight off the board, the only problem is that it has and X-ray protection curcuit, or has a current limter the reduces the output of the fly back. it works fing as lond as you dont short it to ground then it just turns off then you have to reset it. you dont realy need a turn on 555 timer, just find where the on/off pin is and short it to ground i normaly play guess the pin with a gound wire intill i here the flyback turn on.

quicksilver

Thu Nov 04 2010, 05:17PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

Are you talking about methods of cutting CB to make it neat and clean: thus salvaging the whole unit as a section?

If so, you would need to lift the board out with the least damage and isolate the circuit and do some "road mapping" of extra traces & label them. Since it's a salvage you won't likely have any schematic however you could find what indicates power-in, HV out. That wouldn't be too tough if you take your time.

Then determine what cuts the type of board you're working with - with the least amount of cracks. This most likely would be a small hand small-tooth coping-saw. Draw the section & cut while making sure of the labels you have. The demands of the various output elements need to be understood in a general way so as to maintain the circuit so that it's not an open circuit, etc. If the traces are old or applied on the board; speed up when you cut through them so you don't start to peel them from the board.

I have done this on a VERY small scale to keep a circuit intact and it's a bit of work but if you're careful it can be done. The complexities fairly demand that you would have to take into account issues of the standing design & KNOW then to end them or loop them back, etc.

There was another issue where I wanted to just grab the parts but they were VERY difficult to unsolder so I got two hemostats to use as both heat-sinks and as leverage and applied a butane torch on the tracing side in low temp and lifted the parts with the hemostats. It was very fast, easy, & the parts were totally undamaged and wire stubs were clean.
In fact if you get a fairly light torch and a few hemostats, this is a VERY good way of grabbing a complete collection of parts from an existing appliance with minimal damage - as they work as excellent heat sinks and provide leverage you would not have with a hand.

Steve Hobley

Thu Nov 04 2010, 06:31PM

Registered Member #1731 Joined: Thu Oct 02 2008, 02:22PM
Location: Indiana
Posts: 52

Thanks for the response.

I thought about this when I saw that there were 8 hefty pins holding the flyback to the PCB and a bunch of other smaller ones.
It looked like a lot of work to coax the flyback off the board, and so I began to wonder if I could just cut out the relevant bits intact.

I've had a lot of success with using a dremel cutting wheel for this kind of thing.
I just wanted to be sure that there weren't any big "no-no"s with this approach.

Steve

Adam Munich

Thu Nov 04 2010, 07:37PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

As far as harvesting goes, If I don't plan on using the circuit afterward I'll just use a blowtorch to heat up the underside and hemostats to pull out the components. With a bernz-o-matic a FBT will pull out in 20 seconds, and I can remove every part in 20 minutes. Just don't do this inside.

quicksilver

Fri Nov 05 2010, 06:00PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

A Dremel cutting wheel is a speedy and effective choice.

If you DO really take your time you can salvage pits of board that have some variability in their use. There have been times when I have spent virtually no money on this hobby; if I'm simply aware of what's in the trash bin.
-=*=-
Older boards & materials may be made of lousy stuff for your lungs and eyes. Additionally if your working to get delicate things out remember that vibration can be cumulative so it may be a good idea to work w/ eye protection & over a clean soft recovery surface, etc.

Erlend^SE

Fri Nov 05 2010, 10:15PM

Registered Member #1565 Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159

Unless it's from a computer monitor, the circuit "as it is" is not that interesting since it involve too many parts (even most computer monitor mainboards are not that interesting) unless you plan to use it with the yoke.

You may be able to remove the parts that is in the way for your circuits and do it that way, or just crack the board around the LOPT. But my best suggestion is to use a hot-air gun or some torch to unsolder all the pins at the same time and find some circuit on the forum (the original circuit is powered at 50++V and involve some rather high voltages on the primary, you probably do not want that)

Even a screwdriver and prying the board apart from the LOPT actually works somehow :) no soldering-iron needed except for cleanup later.

Antonio

Fri Nov 05 2010, 11:25PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

It's quite easy to desolder a flyback transformer. You need a soldering iron and a solder sucker tool. Everything in a typical monitor board is useful. There is an entire switching power supply with several outputs, and with some care you can also identify the HV power supply and make it work. Many monitors keep the HV output operating even without input signal. You can then just take out the HV terminal and a ground connection and use the entire monitor, unmodified, as the power supply for the lifter.

101111

Sat Nov 06 2010, 03:27PM

Registered Member #575 Joined: Sun Mar 11 2007, 04:00AM
Location: Norway
Posts: 263

Erlend^SE wrote ...

Even a screwdriver and prying the board apart from the LOPT actually works somehow :) no soldering-iron needed except for cleanup later.

I second that! ;)

Antonio

Sat Nov 06 2010, 08:13PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Forcing a transformer out of a board without desoldering is a sure way to break some, if not all, of its pins.
A Dremel cutting wheel is useful in cases where it's impossible to desolder a device with many pins, but it's a lot of dangerous work.

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