Wicked Transformer Hum - Better way to install this?

msignor

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Wicked Transformer Hum - Better way to install this?

Hey guys,

I have a playchoice 10, and I am using a sanyo monitor in it.

I obtained a transformer from a DK to power the sanyo and have wired it to the orginal PC10 PSU on the input side. From what I can tell this just goes from the wall, to the input side of the transformer (where you select the voltages) and that's where I wired up the additional transformer. (see pic)

Everything works - however I have a loud / annoying hum coming from the original PC10 transformer. When I put my hand on the PC10 transofmer I can feel it vibrating (or so i think) and there is no noise coming from the added transformer.

Should I just wire up an outlet from the wall inside the cab and have each transformer plugged in directly from the wall feed? Isn't that what I already have set up though??

Any ideas?

Thanks!
 

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Nope - The PC10 iso has been there all along. The K7000a in it died so I went the Sanyo route instead of converting a standard k7000 to inverted.

I will check out the link.
 
You sure that you didn't just attach one transformer to the output of another? If so, you're overloading it.

Unplug the game and disconnect your new transformer. Check the resistance between the two wires that you were powering the new transformer with. Now check the resistance between the pins of the power cord. Are they exactly the same?

-Ian
 
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OK, yeah, just checked the manual. The original PC 10 power supply runs on 100v, and it's at the OUTPUT of the original PC10 transformer. So, you've chained a transformer onto the 100v output, overloading the PC10 transformer at that winding, and you're stepping the voltage down again, so your monitor is only getting 90 volts or so.

Why are you adding a transformer, anyway? The PC10 original transformer already puts out 100v for the monitors. At least, that's what this manual says. Check and see.

-Ian
 
Let me clarify - This is a single monitor playchoice and it came originally with a WG k7000a and when I DMM'd it I was getting 120-130 on the monitor power cord. I would have much rather preferred to keep it with one iso. I actually tried wiring the monitor to the input side of the ISO originally (before I got the second ISO) and blew the breaker in my house.. Then I read and saw that was a NO NO. since that was the input side of the ISO.

Regarding the hookup - In the picture in my initial post I circled where I hooked up the secondary ISO to power the monitor. Per the manual that's where you also select what your line voltage is.

I assume that since I traced the wires back to the molex plug (that's where the wall plug goes) to that side where the voltage was going into the transformer I could just grab my power from there. Made it seem a lot cleaner.
 
just revisited this last night - was able to check out the original iso that came with the system and compared it to the bob r document. the iso seems good to go and when I take out the new one the hum is definately less noticeable.

for giggles I wired up a wall socket and put the second iso into the wall insead of bridging it to the PC10 iso. now the hum returns... any idea here?
 
Now, let me get this straight. The hum is coming from which transformer? The PC10 transformer or the DK transformer? And you're sure you have the DK transformer hooked up right? There are multiple taps on the input side, to allow you to run it off 100v.

-Ian
 
The HUM is coming from the PC10 iso. It is (was) wired as indicated in the initial post pic, to the 120v input on the DK iso.
 
That sure is a weird problem, since the way you've described it, both transformers should be electrically separate from each other. It's very odd that powering one would cause the second to hum.

Is the transformer mounted right next to, on top of, or touching the other transformer? Some situation where their magnetic fields would interfere? Have you tried reversing the polarity of the DK transformer (i.e. swap hot and neutral going into the transformer - turn the plug over, etc).

-Ian
 
Had some time to play with this.. turns out the hum stops when I unplug the marquee light.. WTF!?

Should I be thinking about replacing the marquee ballast since that is a transformer as well? Not sure where it would be in a single monitor PC10. I didn't see it when taking apart my other cab..
 
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