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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 18th Jan 2019, 10:22 am   #21
The Philpott
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Default Re: Wee Megger - HELP

Was labelled 1.5kV 100nF, Not an electrolytic (different capacitance value to yours as this was a different model of megger)
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Old 20th Jan 2019, 6:36 pm   #22
Johnny_b
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Default Re: Wee Megger - HELP

HI All, after testing with an AVO 8 meter there was not volts on AC or DC. On the Digital Meter there was over 100 Volts AC and about 20 DC.

I dismantled the meter to make sure it was not the brushes. I cleaned the commutator and still not connecting between the two stators. Then decided to pull it apart.

The winding is Open Circuit....between these winding points.

Sadly it is not the Easy one to get at. I guess it is the one that comes up by the side of the stator.....

Not sure what's next

Just thought I would let you all know

Regards
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Old 20th Jan 2019, 9:40 pm   #23
The Philpott
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Default Re: Wee Megger - HELP

Typical example of a high impedance digital meter detecting ghosts! Thanks for reporting back, this helps people in the future with similar repair jobs.

Chances are that if you got another megger for parts it would not have the same fault. (more economic than contemplating a rewind anyway..)

Dave
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Old 21st Jan 2019, 9:41 am   #24
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Default Re: Wee Megger - HELP

Hi, Yes it was a bit misleading with that Digi meter.

As you say, it might give some guidance to others who have the same problem

Regards and thanks to all you guys,,
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Old 19th Feb 2019, 5:00 pm   #25
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Default Re: Wee Megger - HELP

Hi all

After all these problem I decided to pull it all apart and unwind the armature ( see pictures ) to try and see where the break was. Sadly part way though unwinding with my slow speed screwdriver and modified armature holder the thin wire broke. So I then cut the winding off -- got some enamelled copper wire of a similar size and made up a device to rewind it. Had no idea how many turn so just kept going until it look about the same size..

Put is all back together and wow.. the needle moved the wrong way. At least it moved so that was progress.. Guess I wound the armature the wrong way round so just change connection from the outputs and then the needle went to Inf. Still did not work properly so I rewired to the same as the megger picture with the 2 coils. I guess this had been tampered with before..

Got a couple of resistors = 200k and wound the handle... it read 200K... then removed one resister and it read 100k.

So I think I have at least got it as close to working as possible

Just thought I would let you know how I got on

Regards
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Old 20th Feb 2019, 2:29 pm   #26
The Philpott
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Default Re: Wee Megger - HELP

Nice one, what sort of voltage is it producing? My 500v one was showing 450v or more on an Avo after i had played with it.

Dave
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Old 20th Feb 2019, 4:06 pm   #27
Johnny_b
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Default Re: Wee Megger - HELP

I will find out tomorrow at my friend's workshop as he has an old Avo 8.

On my digi one it goes over 200 volts and on the imprinted spec it says 250 volts..
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Old 22nd Feb 2019, 6:59 pm   #28
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Default Re: Wee Megger - HELP

Hi, after using the Old type Avo, on the DC scale it measures at about 235 volts when winding the handle quite fast.

The Imprinted writing on the case says it is a 250 Volt version so a little bit out.

Even the Avo 8 does offer some resistance so on different scales there is a slightly different reading, so used the 1000 volt scale to measure

We tried various resistors from a few Ohms to a few Megs and believe it or not it was almost exact...

So at least I do have something which will give me a clue if I ever have to use it.

Many thanks again to all of you that contributed to my original issue

Regards
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Old 22nd Feb 2019, 7:50 pm   #29
The Philpott
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Default Re: Wee Megger - HELP

Result. I have a '500v' tester made by a rival company which only gives 40 or 50v, and it may well end up being 30 years before I investigate that one as well!

Dave.
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Old 25th Feb 2019, 3:09 pm   #30
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Default Re: Wee Megger - HELP

Three posts moved to a new thread here:-

https://www.vintage-radio.net/forum/...d.php?t=154357
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Old 5th Mar 2019, 6:50 pm   #31
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Default Re: Wee Megger - HELP

I have a similar Megger with an identical fault : The armature winding is open-circuit.

Can you tell me how you re-attached the ends to the armature core, please. They seem to be retained by 4 rivets. Did you drill those out or manage to un-crimp them?
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Old 12th Mar 2019, 11:02 am   #32
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Default Re: Wee Megger - HELP

HI, Yes I drilled them partially out and them prised the ends off. I refitted them by offering them over the partially drill rivets and then squeezed the end on with some pipe grips. Sound a bit dramatic but it just needed a bit more umph to seat it again. Then I dabbed a bit of hot melt glue over the Revit end ( which is slightly sunk ) just to hold it in place to the end cap. Have now used the megger quite a few times and all is well.
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Old 12th Mar 2019, 11:39 am   #33
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Default Re: Wee Megger - HELP

Thanks. When I have some time I'll give it ago (and report back here, of course).
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Old 13th Mar 2019, 9:57 am   #34
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Default Re: Wee Megger - HELP

Hi, here is a link of me unwinding the armature. Have a chuckle ..
https://youtu.be/hlezVMX3kAQ

I had to make 2 simple tools for unwind and wind.

Oh not sure if you have got this far but the needle rollers are not caged so they will drop off when you take the ends off. Just put some Vaseline on the spindle and stick them back when you assemble it.

Good luck
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Old 13th Mar 2019, 12:01 pm   #35
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Default Re: Wee Megger - HELP

Oh by the way... I was only unwinding it to see where the break was but unfortunately after a while the shellac was caught on the windings and it broke.. so never did find that problem///////
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Old 13th Mar 2019, 3:33 pm   #36
TonyDuell
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Default Re: Wee Megger - HELP

Quote:
Originally Posted by Johnny_b View Post
Oh not sure if you have got this far but the needle rollers are not caged so they will drop off when you take the ends off. Just put some Vaseline on the spindle and stick them back when you assemble it.
Yes, I found the loose rollers the hard way. I stuck them back with bearing grease (I can't believe it's that critical what to use, it is not run for long
periods).

The rear bearing (commutator end) is the easier one. After fitting the end housing, you can remove a little plate from over the end of the spindle and insert any escaped rollers that way.
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Old 14th Mar 2019, 4:46 pm   #37
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Default Re: Wee Megger - HELP

Yes I also found that was a nice extra bit of assistance when re-assembling..

One other thing, when I rewound it I did not make a note of which way I unwound it ( before I cut the whole lot off with a Stanley knife after the winding broke )

When re-assembled and I connected the meter, I though all was great until I noticed when I fitted the Ohm scale back the needle was going the wrong way. So I have to change the connection output from the brushes, the top connection was connected direct to the meter but now the bottom brush output is connected to the meter and the top one connected to where the bottom one fed...if you see what I mean. Just had the DC the wrong way round but works correct once I change that... just a hint,,,,
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