Interesting point. will try that later. Was realy after a test that didn't require cutting a compressor apart, that then becomes a point of no return.

Its not cooked Frank its just diferent coloured enamel coating.

No its beyond repair Frank. Have since discovered  the windings aren't Delta but Star wound. Theres a shorting link that creates the center of the star winding, so I removed it & checked the resistance & inductance of each individual winding. They were closer to the same values. But on re connecting the shorting link now find the compressor will actualy run. So the only thing I have disturbed are the internal conections. Thanks for your input guys, makes you re asses what you have done or missed.

-- Edited by DeBe on Thursday 10th of December 2015 01:12:36 PM

Darryl, years ago I built a tester that gives a ringing waveform for different coils, which was mainly used for LOPT transformers, but the output can be selected for other sized coils. You could consecutively ping across each of the coil pairs at the inputs and compare the resultant waveform on a CRO. You could use the waveforms from a known good motor to determine whether the one under test is stuffed or not.

You would get something similar to this (this is a pic I pulled of the net just as an example)

I used to download the waveforms to a computer, as well as waveforms of the new replacement LOPTs, and save them for comparison with other LOPTs I suspected as being bad.

Bob Parker designed an FBT tester as a kit for Electronics Australia. This kit was sold by DSE and others. I expect that one could modify the frequency in his design. Alternatively you could replace IC1a with a 555 timer.

http://members.ozemail.com.au/~bobpar/fbt.htm
http://members.ozemail.com.au/~bobpar/k7205.pdf

-- Edited by dorian on Friday 11th of December 2015 08:32:27 AM

03 if you find the circuit I would be most interested.

I found it and opened it up, but now I remember that it wasn't a kit, but one I got details from somewhere? and built on a vero board. I'll trace out the circuit when I get a chance and try some tests on a couple of different coils. The other thing I realised while searching for it was that I no longer have the desktop computer I used to use to save the waveforms to, and none of my laptops have a serial port. Except for a very old Toshiba notebook that I almost threw out a couple of weeks ago. And I had to download software from the Tektronix website because I might have lost the original software I had. I haven't used the DSO in over 10 years now.

OK, I have been playing around with the coil tester on a couple of motor windings, and these are the results.

I had 2 different motors, both 240VAC, but different constructions. I tried them both at the different switch settings on the tester and viewed them on a DSO.

The tester, I'm pretty sure, I built from a schematic that was in a pommy TV servicing magazine that I sometimes got when I had my electronics repair business back in the mid 90's. I haven't traced out the circuit yet, because the way I built it (rough and ready) I have to unsolder the pot and switch and sockets to remove it from the box.

The tester.

 

The tester puts out a series of pulses or different shapes (selected by the 3 position switch) at a frequency of between 66Hz and 124Hz (adjusted by the pot) roughly when not loaded by a device under test. The pulses are between 60mV p-p and 80mV p-p also depending on the switch position, and also when no device under test connected.

Here are the un-loaded pulse trains using switch positions 1 to 3 respectively:

 

Here are the motors I used for testing:

 

Here is what happens when the photocopier motor is connected across the tester, leaving the the time base the same for each position, to show the differences in waveforms produced:

 

Here's what they look like when you adjust the display for a usable waveform:

As you can see, you can get a decent enough ringing pattern to be able to see if you have shorted turns, especially if you have known good waveforms to compare them with.

Here is what the other motor looked like on the tester:

 

These waveforms are also pretty good for the purpose of looking for shorted turns. Especially in position 3 in the last pic, where you can see a nice symmetric waveform, with a smooth amplitude decay.

Hopefully I'll get some free time to pull the tester apart so I can trace it out. there are only about 8 components in total, but the way I put it together, it isn't easy to get at.

We bought a NV-2000 when we were in Malaysia back in 1981, from memory they cost about $1,500.00 in Aus at the time. We also bought a VHS Video Camera like this one, Which were well in excess of $2,000 in Aus at the time.

Hi 03 Troopy;

            Yeah great recorders of the day, only down side was they were very heavy in weight and the rechargable battery only lasted about 30 Min's. Old school recorders and now aeirloom material. Had a clean out of my store room ( 2nd bedroom ) the other day and one of the things that went to the local tip was a hitachi vhs (c) camcorder still worked, last time i used it but the way of how things are this days beening a throw away society, now one wants 'old school' same as the do do bird. 

And me to had a big clean out of trade mag's etc a couple of years ago. You name it, if it wasn't used or out of date, out it went, a couple of valve school PA amplifiers ( Pararell push pull 807 valves ((4 )) and about 500 volts on the plates ) good for a couple of 100 watts Weighed a ton , but again old school, serperate power supply and serperate radio tuner, built to last and last all in a steel case and made by AWA i remember these things, ran all day 5 days a week. Not like the rubbish that is forced on to the industry these days.

Sorry you guys for getting off topic, once i get on my soap box, their is no stopping me

-- Edited by valiant81 on Friday 18th of December 2015 05:49:59 PM

Thanks for that. Have printed it all of & will build it, only part I will have to buy is the IC. Will eventualy get back to you.

Hi Darryl, do you get any output at all, using a resistor across the output?