Isolation transformer source

Given your supreme command of the English language it's not a surprise you don't understand what 'isolate' means...

--
*I don't suffer from insanity -- I'm a carrier

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Nice price. I'm working on a 1KW HP 6032A power supply (with outputs unloaded in this case, so I don't need *too* much current capability) and need to connect my scope to the hot side of a switching transformer - specifically the source and drains on the output FETs.

Service manual: (3MB)

Page 113 shows the schematic of the FET board.

With an isolation transformer, I *think* I would connect the scopes GND lead the source of Q1 and probe the it's gate to check the it, then move the scopes GND lead to Q3's drain lead to check it's gate drive.

Given that, would that Ebay transformer be the right choice, and do I need to isolate (disconnect) the ground on the 6032A power supply under repair?

Thanks.

Galvanic. Thanks - didn't realize there are different kinds. Don't want to kill myself!

It certainly seems to me stupid to have the same name for different devices like this. What is the point of an isolating transformer which doesn't isolate?

--
*When a clock is hungry it goes back four seconds*

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Thanks Chuck. Looking at these for the moment:

A bit more than I wanted to spend and a little less current capability, but those may be the breaks.

You need to make 100% sure your life insurance is fully paid up.

This is a "bad idea". Better to use a differential input and two probes. Do you have a two channel scope with invert on channel 2?

Tom

"Dave Plowman " Rabid Pommy Nutcase"

** Shame it is not so in the USA

- you Steaming Great Fuckwit ...............

... Phil

That SHOULD be the correct isolation transformer. And yes, the ground must be isolated. Note that this may well leave the metal chassis of the power supply at some potentially lethal voltage, so use extreme caution.

Somewhere in my kit (probably with the isolation transformer I can't find) is an adapter to use a grounded (three prong) plug in an ungrounded (two prong) outlet. I used that when working with any devide that required the isolation transformer. I also carefully verified that the isolation was indeed effective; I had no desire to watch my scope probe's ground lead vaporize.

PlainBill

But I'm not in the USA and neither are you. However, at least I know not to use bad language when visiting. If you'd ever known your parents they'd have likely taught you the same.

--
*If at first you don't succeed, redefine success.  

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

That would be news to large numbers of electronics technicians who had to use an isolation transformer when servicing TVs and other 'live chassis' consumer electronics. There IS a reason the advice was 'to always keep one hand in your pocket'.

PlainBill

On Sat, 12 Jun 2010 10:20:10 -0700, PlainBill47 ??o??:

Serviced many GE VIR portables with a Sencore PR57 Powerite.

If using a proper isolating transformer, there will be no reference to ground even with a 'live' chassis. The only way to get an electrical shock is to touch both outputs from the transformer.

--
*Why isn't there a special name for the back of your knee?

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

You can do it anyway you want. Just that many good scopes have a way to add the inverted second channel and can be used to look at a signal that is raised above ground. No isolation transformer is needed and it is IMO, safer.

YMMV.

Apparently you assume that I didn't understand that.

-- Cheers, WB .............

That advice was quite valid when two channel scopes weren't seen outside of a factory or research center.

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

Not true. You connect the chassis of the UUT to the test equipment, so ANY voltage you contact inside the UUT is referenced to ground.

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

"tm"

** The problem with that idea is the very limited common mode range available with that scope function.

The buffers on most ( analogue) scopes become overloaded with input signals that exceed full screen hight by a factor of 2 or 3 times.

Say you want to examine a 1 volt p-p signal and you set the scope input atten to 0.5 volts per division - then the largest undistorted input allowable is gonna be about 0.5 x 8 x 3 = 12 volts p-p.

Not much use with the ACTUAL common mode signal is several hundred volts p-p from rectified AC supply.

** Fraid that is just not true when dealing with off-line SMPS.

.... Phil

"Wild_Bill Top Poster from Hell"

** Could not be plainer that you did NOT understand the issue.