isolation transformer

[adidas1984x]

My question is do they go bad and is it ok to use one if not needed. and which is input and which is output and how can you check to see if the iso transformer is still working 100 percent correctly. Do you check the ohms and resistance??

[Sarver Systems]

My understanding is that it is a 1:1 transformer.

Whatever voltage you put in, get transferred over to the other side as the same voltage.

110V in, 100V out.

Test it by plugging it into an AC source, and measure the AC voltage on the other set of terminals.

I'm sure others will chime in on this, and I hope my info is accurate and helps.

[jennifer]

     Well yes in theory, but depending on the circuit your trying to isolate may change your transformer needs, and is it a step up trans.?, This will raise your output voltage but lower your amps.... Personally I don't use them if I don't need a floater, I feel safer on a earth ground, and opt for the simpler overall circuit design.

[adidas1984x]

Here is the unit

[jennifer]

    Hook your line to the bottom terminals.... And take a voltage reading on the top terminals, it should be the same voltage (or really close). and then you will be iso. at 1 amp.

[Sarver Systems]

And the ground lug goes on one of the screws that you use to attach it to the cabinet.

[jennifer]

    and if you plan to keep it around for awhile, you may want to squirt some high temp silicone in that cracked case to keep moisture out.

[adidas1984x]

Is there a way to check it by measuring the resistance on it as well? not trying to sound dumb just never had to use one of these before. Im going from a u5000 to a k7000
which i heard is a better chassis

[jennifer]

     The short answer would be no, not necessary, but an ESR meter (equivalent series resistance) could do it... Resistance however isn't your primary concern, the amps is the rating you need, if that falls short in your circuit, then shorted windings (or other problems within your circuit) would be suspect.

[jennifer]

      Although it could also be said    Volts divided by current = resistance.... Therefore measure your input voltage and divide by 1 amp, then on ohms scale measure the two top terminals (and since its a 1/1) the two bottom terminals, these readings should match, But again, that chassis most likely doesn't need to be isolated. and the fuse will protect it from over current conditions. 

[adidas1984x]

and mounting it in the bottom of the cabinet next to the power supply is that ok?

[lilshawn]

the k7400/k7500  series monitors use a switch mode power supply. Isolation shouldn't be required.

the older "k7000" with the  big resistor and regulator DO require an isolation transformer.

i know a lot of people just say "k7000" when referring to the k7400/k7500 since they are basically the same monitor chassis without realizing there is actually a k7000

[adidas1984x]

it has a tag that says needs one

[jennifer]

    In the area of the P/S would be fine.... I would keep as far away from the filter caps as you can so you don't create any undo noise in your power supply.   

[adidas1984x]

Just bolt it down to the bottom of the cabinet wood and let it ride?

[lilshawn]

Just bolt it down to the bottom of the cabinet wood and let it ride?

wherever is convienient. just put it in a spot where you aren't going to be tempted to brush against it if you have to work back there.

[adidas1984x]

ok so i put it in my cabinet and put the 120 to the bottom and outputted the top to the monitor but i did check the voltage first on the bottom of the transformer its at 119 120 volts. top is at 129 130 volts ..... so im guessing something is wrong here. I didnt hook up the chassis yet i wanted to measure voltage to be sure . any suggestions?

[jennifer]

      Jennifer would be a little nervous to use that, its not at 1/1 like its rated, you could hook the output up to a terminal strip and knock the voltage down a bit with a sugar cube (resistor), but If it was mine Id try a different transformer.

[ed12]

yes un-loaded it is a true
1.1 to 1.5 to 1 iso
ie: 117-120vac in give's u 129-130vac hence the term 1.1 to 1
so easy put
place in 50 volt's get 1.1 more :un-loaded out:
50-x-1.-1 =50.5
120-x-1.1=120+.1-x.12=.12 so

120+.12=122vac or where about there.

easy way to find out is just hook a light blub to it
ie 120v 60 watt,that will load it..then measure it
u will find it going down real fast under load

ed

[adidas1984x]

I reveresed the imput and output and now it show 109 volts to the monitor ..... any ideas?

[jennifer]

    Yes, now its running backwards....(**JENN does a slo-mo backwards move) kinda like this, giggle, snort!!!.... No really, Eds crazy math is your answer, what hes saying is a load on it will pull the voltage down.

[adidas1984x]

Would it work if backwords?? or do i need to take a chance and plug it back and see what happens??

[ed12]

thk-u jenn
yes the math work's backward's also
so 117 on the 1.1 side in will give u about 110 on the primary side..
do yourself a fav..stop beating your head and get a light bulb out >60watt<
and rewire back to normal
load the bulb on the secondary side,measure..u will see a drop..

ed

[adidas1984x]

OK project time when I get home thanks for all the help. I will post tonight when I get home.

[lilshawn]

basically the voltage will drop down once you have a load on there.

you can verify by wiring up a 60 or even a 100 watt lightbulb (if you can find it) to the output and measuring the voltage again.

it's just high because it's running unloaded.

[adidas1984x]

ok so I put a 60 watt light bulb on it and the voltage went from 129 to 128.1 sooooo................any suggestions?

[ed12]

thats about right...60 watt = .6a=600 ma
100 watt = 1 amp = 1000 ma
iso is to drive 5 amp in-rush = 5000 ma
it's about right..voltage should go down with load as u just proved it to yourself
>
ok so I put a 60 watt light bulb on it and the voltage went from 129 to 128.1 sooooo................any suggestions?<

now u have 2 choices
ditch it and get a 1-1 iso >spec that 1-1<
or just the monitor into it..it does have a load input resistor...that is excatley why it is there.
then mesure it..should have pulled down to about 120-122 +/-10% on line voltage
btw ohm's law apply's here

ed

[adidas1984x]

im just nervous dont want it to blow my chassis

[adidas1984x]

Ok it works but i cant get the image to get any bigger it has a black line above and below the image and none of the board controls make a difference any suggestions here is the pics

[Sarver Systems]

There are controls across the back of the mainboard, and controls on the remote board.

Make sure you try all of them. Horizontal height is what you're looking for, I do believe.

[adidas1984x]

adjusted all pots on neck board and chassis and no difference still will not fill the top and bottom of screen. I think the vertical is bad

[ed12]

excuse me
why would u adjust the control's on the neck board ??
they are your screen cut off control's/over-all color gain control's

u want horz width and or verticial size
which ARE NOT on the neck board

ed

[jennifer]

     Id be curious if that chassis is for that monitor.... Where did you get all this stuff???.... Oh FWIW, I looked at the ebay for 1/1 iso. trans. lots to choose from, Iam still of the opinion that one has issues. (really surprised that bulb load did nothing.)

[adidas1984x]

i meant adjusted the remote board not the neck board. and with the chassis installed it dropped to 125.5 volts

[jennifer]

     Now that is a FUN fact...

[ed12]

no no jen the !wacky! math is the fun fact
i over e =r
u can play with it any way u need

for the record that is the value i expected

and if it is just the remote board and not the neck board
i will help u along..

ed

[jennifer]

    Yes I follow the math, I was trying to point it out earlier before you just did the math.... Its when the bulb didn't draw it down like predicted is when I got all concerned.

[ed12]

no jen u were spot on..
but what u did not take into accout was a 60watt bulb
60 watt at 120vac = .6 of an amp >not a real havey load
where 150 watt is..

even though that iso is rated for 1amp,it can handle 5 amp in-rush current
so then we know our upper value for the transformer..
it come's down to the main fuse of the monitor
to tell us the exact load
ie 3a/5a/8a
we can then do the math right..until then it is the best guess pre-say.

and u must forgive me,as i some time's think most ppl took 101/102 electronic's
and i am by no means a snob..it is just year's of working with it


ed

[jennifer]

      I got all OCD and locked myself in the lab.... After hooking a 1/1 up to the scope apparently what is happening is the draw is saturating the 1amp,  (And according to Ohms law) this changes the volts, Very interesting study.

[ed12]

welp for a man u got a very sexey ass
but back on topic
that is what to happen
current=draw
then u go >i< over voltage
etc etc,the law work's 3 way's
i over e =r
e x r =
r divided any of the above =
then u carry on on to volt amps >va<
which = watt's which = current=reistanice,which = wire size +winding's+
go fig
btw u are now in engeering range

ed