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 Rewinding power transformers or does anybody have a spare one of these?
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 Return to top of page · Post #: 1 · Written at 3:35:18 PM on 8 June 2017.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

My poor Emperor is sick, it's been making a funny waxy smell and sounds a bit like a deep fryer, mind you it's still working but when I removed the chassis, there is a pool of wax under the transformer, I noticed the smell after running it this morning for about 3 hours, funnily nothing, even the tranny didn't feel hot from the top of the chassis, yet underneath it was.
Obviously the 1000 ohm field coil speaker was too low in resistance even though the voltages seemed right, I even put a 1.2K 5 watt resistor in series with the field coil to give me 2.2K like the original speaker, however I think the tranny has had kittens as for some reason I have 270 volts on one side and 385 volts on the other side instead of an even 385, and the frying noise continuing, even with no rectifier in place. I'm guessing a winding has gone poo?
So does anybody know where I could send it to have it re-wound? or does anybody have a spare 385v-0v-385v transformer with a 5v and 2.5v filament tap?
I figure the only way forward is to replace or rewind it.
Cheers. Jamie.


 
 Return to top of page · Post #: 2 · Written at 3:50:06 PM on 8 June 2017.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1575

There is a guy in the services directory that rewinds trannys


 
 Return to top of page · Post #: 3 · Written at 4:31:33 PM on 8 June 2017.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6013

I noticed the smell after running it this morning for about 3 hours, funnily nothing, even the tranny didn't feel hot from the top of the chassis, yet underneath it was

That is the chief reason that I will never leave any old radio powered on when I am not present.

Causes for such overheating will vary, but the result can be truly catastrophic.

You never know what might be in members' junk boxes, but a rewind is likely your best option in this case given the 2.5 volt filament requirement.


 
 Return to top of page · Post #: 4 · Written at 5:41:00 PM on 8 June 2017.
Redxm's avatar
 Location: Tamworth, NSW
 Member since 6 April 2012
 Member #: 1126
 Postcount: 444

David Browne is the man you want. http://www.transformerrewind.com.au/

I have dealt with him and he is well priced and quick

Ben


 
 Return to top of page · Post #: 5 · Written at 7:20:54 PM on 7 July 2017.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

Yes David Browne is the man. He has re-wound my transformer which had shorted out on one side of the HT winding. He has also rewound my speaker transformer and found and fixed a broken voice coil wire, so I'm very happy with him and this forum for suggesting his services!


 
 Return to top of page · Post #: 6 · Written at 7:38:47 PM on 7 July 2017.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6013

Good feedback.


 
 Return to top of page · Post #: 7 · Written at 10:45:56 PM on 7 July 2017.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4347

The objective now is to go back to the schematic and ensure every component in it, is in spec. Sometimes a tranny will fail all by itself especially if the windings get loose, or there is insulation failure (moist storage).

The other is it being caused to fail: E.g.Shorted caps (mostly the electroytics). I do not think that some actually appreciate just how much extra loading a group of leaking caps can contribute too problems. Leaking positive onto the control grid adds to the problem.

I note 10mA on a filter cap is considered by a tester here a fail & that in itself is one hell of a loading. Modern ones do not draw that sort of current. Most of the PSU's took the current of the Filters into account.

I use a voltage close to the non polarised caps working or specified test volts to leakage test them, using an insulation tester. The Palec VCT uses 225V and a neon. The same instrument as before:... Screen decoupling below 50 Meg is a fail; Coupling cap, below 200 Meg. The latter may seem odd but valves are voltage driven & as suggested, positive leaking onto a grid that is meant to be negative, is far from helpful.


 
 Return to top of page · Post #: 8 · Written at 10:46:31 PM on 7 July 2017.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1575

If you wish please email me a picture of your transformer. Top and bottom I may have one for you.


 
 Return to top of page · Post #: 9 · Written at 11:06:48 PM on 7 July 2017.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6013

^ See post #5. Problem solved via repair.


 
 Return to top of page · Post #: 10 · Written at 8:57:47 PM on 9 July 2017.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

Yes, thank you Carl, however David has it all fixed for me now and very reasonably price wise I must add! Very Recomendable!!!


 
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