transformers never go bad?

720fan

Member
Joined
Jul 16, 2010
Messages
56
Reaction score
0
Location
newport beach, California
i have heard that transformers never go bad, but i am working on my 720 degrees game right now and all i can think is that the +12 volts that is supposed to get to the audio board is not working? i get no audio, no picture, and the video and cpu boards show the proper +5 measurements.
is there an easy/safe way to measure the voltages coming off the transformer so i know its getting power and working? i know the 2 wires coming off that go directly to the monitor are giving power, but not sure about the 3 (red, orange, violet) going to the fuses then to the audio pcb...and there is the red/white common wire as well coming off...all the fuses show continuity and are the correct type of fuse.

any ideas?
if this is a transformer issue, is there an easy replacement or fix?
thanks
joe
 
FWIW, I have an Atari power brick with burns where the wires come out of the transformer. I suppose it happens, just not often.
 
Transformers very rarely go bad in video games, but it can happen, especially if someone bypassed a fuse and the bridge rectifier blew. Check the voltage a the output of the transformer. The wiring diagram in the manual will tell you what wires carry what voltage.

-Ian
 
to do this i put the black lead from my meter to the common and the red to whichever voltage im testing before it hits the fuse correct? and set it to 200v?
thanks
joe
 
I bought a Future Spy project a while back that had a yellow sticky note that said "transformer smokes". I had not seen that before but sure enough soon as I turned it on it started smoking like a cheap cigar.
 
hmm, so maybe there is a chance mine is bad? how do i test it properly and where do i find a good replacement? the original part number is 142044-001 from atari.
thanks for all the input so far.
joe
 
It happens but not often. In most cases when people think they have a bad transformer they are just not taking their readings at the right place.
 
i have heard that transformers never go bad

It's not common, but they DO go bad. As a common example, a flyback is a transformer and obviously they go bad.

The windings are made of enamel coated wire wrapped hundreds of times. The enamel is like wire insulation to prevent shorts. When over heated, the enamel cooks and wire windings short out. This increases current flow (and heat), further heating the wire.

But typically, transformers do not go bad unless overloaded.
 
hmm, can someone post a step by step way to test a transformer for voltages with a digital multimeter safely?
thanks

A transformer output cannot be tested with a ground reference, you must test across the secondary windings. The output from a transformer is AC, so you must set your meter accordingly. Polarity when checking AC is not important. Find the secondary windings, usually there will be two, but some transformers are center tapped, so then there are three.Measure across them, and see if you're getting power. The manual should tell you which wires carry which voltage.

Example, a simple center tapped transformer, primary 120v, output 12-0-12. The primary winding has two wires, and gets connected to the 120v mains. The secondary winding has three wires, for example, two orange wires and a yellow wire. The yellow wire is the center tap, the orange wires are the beginning and the end of the secondary winding. Measuring across the two orange wires gives you 24 volts AC. Measuring from either orange wire to the yellow wire gives you 12 volts AC.

Many transformers in games have multiple secondary windings - each isolated from each other. They're just all wound on the same core. So, in an Atari game, you'd have one primary winding to connect to the wall, and several secondaries. One for the monitor (isolation), one for the AR-II's supply, one for the coin door lamps, etc. These outputs are all fused, so that if something shorts out, then the transformer won't burn up or catch fire.

Note that when measuring transformers, their voltage outputs are specced under load. So, if there is no load, expect the voltage to be somewhat higher. This is normal.

-Ian
 
thanks ian, this makes sense... i am still unsure how to exactly test this specific transformer. here are some pictures i took of it and the schematic that shows what it is supposed to be putting out... i take it i put my meter on AC, and set the dial to 20 on the ~/_V section.. does anyone by looking at this know where to test across and what my readings should be?

i do think the blue/white - brown/white section is working because my monitor powers up.
thanks
joe
 

Attachments

  • 720transformerwschematic.jpg
    720transformerwschematic.jpg
    82.8 KB · Views: 26
  • transformerbackwnotes.jpg
    transformerbackwnotes.jpg
    75.7 KB · Views: 26
Alright, here's how to test it. Set your voltmeter on a/c, then check with one lead on the blue and white, and one lead on the brown and white. You should get between 110-120v.

That's your monitor, like you said it's probably fine.

Next, put your black 'common' lead from your meter on the white and red line. That's your ac 'ground' as it's labeled on the image. Then put your red lead on each of the other three colored wires, and see if they give the proper voltage. AC isn't really regulated so it'll be slightly off, but as long as you're within a couple volts you should be good. Like don't freak out if the 12v is 14 or something.
 
Some of them do...

Megatron.jpg
 
yes and lets not even get started about transformers 2 the sequal ;)

so, if i have a bad transformer that needs to put out 12vac hi, 12 vac lo and 18vac as well as the 110-120 for the monitor, what is the best part to replace it with that is easily available?
 
Back
Top Bottom