Author Topic: Eden Metro Transformer specifications  (Read 150 times)

Offline nicbrown

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Eden Metro Transformer specifications
« on: October 31, 2018, 08:35:12 PM »
I am currently tidying up a Metro DC210XLT that is dated 1997.

It is functioning well, but has a pretty high level of transformer hum that is audible through the speakers. I have mitigated this somewhat by rotating the transformer and fixing some of the wiring inside in positions where they pick up less noise. I may end up shielding the speaker switch wires as they seem to run very close to the transformer.

In my troubleshooting, I have checked the output of the transformer, and I can’t find any information to tell me whether this is in spec.

The secondary outputs measure both measure 58.3v unloaded, and the power supply board measures 78.7v at the outputs to the preamp.

The transformer is presumably the official Talema/Nuvotem toroidal from that era. The label has the following:

TR-500   31-0030
1749-SP3S2C
3297

I assume this is custom made for Eden. The only thing I can decode is that it was likely made in feb/mar 97, as the numbers don’t match product codes on the Nuvotem site. Based on the dimensions and output, I am assuming it is a 500va with 55v secondaries.

Any information on the factory fresh specs of this transformer, or any equivalents used in pre-2003 amps would be appreciated.

Offline Bassmann1968

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Re: Eden Metro Transformer specifications
« Reply #1 on: November 01, 2018, 02:51:06 AM »
Hi Nic and welcome to the Garden!

Your assumptions  are correct. 55V and 500VA.
Unfortunately, I don't have more information about the transformers.
In my experience, the best position for the transformer is, when the harness coming out of the transformer is pointing toward the power inlet of the enclosure. Is it the same for you?
Rock on!
Armin

PLEASE LIKE EDEN ON FACEBOOK!!!
No schematics available!!! Don't ask for it.
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WTP-Pre,1350,WTX260,WT300/400,WT1000,WTX1000N,NAV,WTDI
D112XLT,D210XST,D410XLT,D810RP,DNS410,DNS112

Offline nicbrown

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Re: Eden Metro Transformer specifications
« Reply #2 on: November 01, 2018, 05:36:09 PM »
Thanks for that info. 55v is a stock item for many transformer suppliers, so replacement will be relatively economical if it comes to that. I have since read that transformer hum in these amps is more prevalent in 230-240v countries. I don't think it is near failure, but the windings aren't as tight as they were in 1997.

In the same price/size ballpark, Nuvotem has an exact match, a 500va encapsulated version, or a 625va that adds almost another kilo of weight, but might 'sing' less under load. Or at least will run cooler without being too dramatically oversized. This is one amp where another 700+ grams isn't going to be too noticeable!

Rotating the transformer did drop the noise level a bit, but it was in the order of 20% of perceptible noise rather than being completely silent. I have made more gains moving wires around until I find a sweet spot, then fastening them down with stick on cable clips. I have also secured the wires leading to the primaries and secondaries with zip ties, separating the bundles like automobile ignition leads. I think I will shield the speaker switch wires with earthed copper braid (and heatshrink insulation) next. You could probably replace this with shielded speaker wire or route a longer wire away from the transformer, but I have the braid lying around.

Offline Bassmann1968

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Re: Eden Metro Transformer specifications
« Reply #3 on: November 02, 2018, 06:15:59 AM »
Hehe, nobody will notice the extra 700 gr. for sure :D
I would also measure with an oscilloscope to see where the noise is introduced.
Maybe in the power supply board? There you could easily filter some of it with a capacitor.
Rock on!
Armin

PLEASE LIKE EDEN ON FACEBOOK!!!
No schematics available!!! Don't ask for it.
;)

WTP-Pre,1350,WTX260,WT300/400,WT1000,WTX1000N,NAV,WTDI
D112XLT,D210XST,D410XLT,D810RP,DNS410,DNS112