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Old 14th May 2021, 1:14 pm   #1
Strange Brew
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Default Faulty power Transformator - replacement?

Hi.

I hope this is the correct place to post this.

I have an RTW volume meter and its power supply is buzzing really badly.

Unfortunately, I can't seem to find a replacement on the general web so I was wondering if anyone here could point to a possible replacement?

I've tried to get in touch with Schaefer but had no replies. Not even sure if they're still made.

Many thanks
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Old 14th May 2021, 1:53 pm   #2
WME_bill
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Default Re: Faulty power Transformator - replacement?

Transformer troubles.
It certainly sounds as though the transformer insulation is failing., but first just check that the unit is bolted down firmly to the PCB and the laminations are firmly clamped together.
Are any windings connected together on the circuit board. I suspect the use is as 100-0-100v at 9ma to feed a nixie tube display, and 8-0-8 at 200ma for the main electronics. This latter is presumably rectified and cut down to a 5 v rail through a regulator IC, such as 7805. And perhaps a negative 5v rail through a 7905.
You must tell us a bit more about the circuit components around the transformer.
The primary is two 120v windings, so probably connected in series for UK mains. Perhaps you can confirm.
With this information, it should not be difficult to identify an alternative and any necessary mods to the PC Board.
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Old 14th May 2021, 1:58 pm   #3
Strange Brew
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Default Re: Faulty power Transformator - replacement?

Hi Bill.

I'm afraid you have one up on me at this point, that is... I really don't know much about these things or what is wrong or anything about the circuit.

I can give you the model number : RTW 1206D 'plasma PPM display'

Do you think finding a direct replacement supply unit be hard to do?
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Old 14th May 2021, 4:10 pm   #4
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Default Re: Faulty power Transformator - replacement?

Have you tried RTW, Schaffer are unlikely to deal with one off quantities.
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Old 14th May 2021, 4:19 pm   #5
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Default Re: Faulty power Transformator - replacement?

Hi.

I've tried RTW too... none left in stock apparently.
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Old 14th May 2021, 7:17 pm   #6
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Default Re: Faulty power Transformator - replacement?

Hi, unfortunately this type of transformer fails all too often in professional equipment, and while replacements for single voltage types (12+12V) are easy to find, this combination will be difficult. It is a potted transformer so a rewind is not possible.
Best course of action is to fit 2 separate transformers id there is room in the case

Ed
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Old 15th May 2021, 11:52 am   #7
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Default Re: Faulty power Transformator - replacement?

Ugh... thanks, Ed.

This doesn't look too promising, does it.
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Old 15th May 2021, 3:07 pm   #8
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Default Re: Faulty power Transformator - replacement?

Quote:
and its power supply is buzzing really badly.
Just buzzing or also getting hot?
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Old 15th May 2021, 7:33 pm   #9
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Default Re: Faulty power Transformator - replacement?

Quote:
Originally Posted by Ed_Dinning View Post
Hi, unfortunately this type of transformer fails all too often in professional equipment, and while replacements for single voltage types (12+12V) are easy to find, this combination will be difficult. It is a potted transformer so a rewind is not possible.
Best course of action is to fit 2 separate transformers id there is room in the case

Ed
It could well be a custom transformer made for that particular product. We've safety tested custom transformers at work. I note it hasn't got any safety marks from authorised test houses....just a CE mark which doesn't mean very much. Most likely this indicates a relatively short run of this particular transformer.......it would not be economical to have a short run of transformers tested by UL or VDE so the manufacturer would basically use approved components and do his own testing and satisfy himself that it met the requirements.

All this means that the chances of finding a proper replacement are slight to impossible.
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Old 17th May 2021, 11:40 am   #10
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Default Re: Faulty power Transformator - replacement?

Quote:
Originally Posted by merlinmaxwell View Post
Quote:
and its power supply is buzzing really badly.
Just buzzing or also getting hot?
Hi. Both really. It does get quite warm
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Old 17th May 2021, 11:41 am   #11
Strange Brew
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Default Re: Faulty power Transformator - replacement?

Quote:
Originally Posted by Sideband View Post
Quote:
Originally Posted by Ed_Dinning View Post
Hi, unfortunately this type of transformer fails all too often in professional equipment, and while replacements for single voltage types (12+12V) are easy to find, this combination will be difficult. It is a potted transformer so a rewind is not possible.
Best course of action is to fit 2 separate transformers id there is room in the case

Ed
It could well be a custom transformer made for that particular product. We've safety tested custom transformers at work. I note it hasn't got any safety marks from authorised test houses....just a CE mark which doesn't mean very much. Most likely this indicates a relatively short run of this particular transformer.......it would not be economical to have a short run of transformers tested by UL or VDE so the manufacturer would basically use approved components and do his own testing and satisfy himself that it met the requirements.

All this means that the chances of finding a proper replacement are slight to impossible.
Hmm... that's a bit of a barstool.

It's a real shame, it's a lovely little unit.
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Old 17th May 2021, 4:40 pm   #12
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Default Re: Faulty power Transformator - replacement?

You could always put two transformers in an external box.

Ungainly, but OK if it's used as fixed equi[ment.

David
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Old 17th May 2021, 4:55 pm   #13
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Default Re: Faulty power Transformator - replacement?

Quote:
Both really. It does get quite warm
A thing to try take it off the board or remove the rectifiers and power up, does it still hum/get warm? If it doesn't there is something downstream that is loading it, if it does the transformer is bad.
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Old 28th May 2021, 6:27 pm   #14
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Default Re: Faulty power Transformator - replacement?

Hi!

Get a small 9V𢠫V transformer of about 510VA that will fit in the unit or on the PCB and use one of these kits for the high杤oltage supply:

https://www.ebay.co.uk/itm/High-Volt....m46890.l49286

The Operation Manual for these is also a Service Manual with schematic diagrams and parts lists, so you can use the information in it to help you get the correct h.t. line voltage for the display!

I note the RTW 1206D has a metal tubular stand has this a hollow space you can use for a small 9V transformer and the PSU kit I suggest?

Chris Williams
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