Can toroidal & E-I co exist? - diyAudio
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Old 27th October 2006, 04:59 AM   #1
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Default Can toroidal & E-I co exist?

Have assembled a 4 channel amp for which the Front amps are powered by a torroidal and the rear amps powered by E-I. For some reason the E-I tends to get damaged after a months use and heats up rapidly. Its a recurring problem and its the 3rd time I had to replace the transformer. Have replaced the rear amps before, but this doesnt help. Could it be possible that an E-I is not meant to be kept too close to a torroidal as it would cause some sort of inductance?

Thanks
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Old 27th October 2006, 06:41 AM   #2
AndrewT is offline AndrewT  Scotland
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Hi,
it's not a toroid/EI compatibility issue.

What temps are inside the amp casing?

Are the EI running hot?

Could the EI be mis-wired (phases)?
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Old 28th October 2006, 06:36 AM   #3
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Thanks for your reply Andrew.
The EI has been removed from the cabinet and it still gets heated up without any load. There's a shorting between the primary & secondary. This has happened before.
Forgive my ignorance, but how do i connect 2 tranformers in phase?
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Old 28th October 2006, 07:35 AM   #4
AndrewT is offline AndrewT  Scotland
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Hi,
does your EI have twin and/or multi-tapped primaries?

Does your EI have twin secondaries or centre tapped and/or multiple secondaries?
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Old 28th October 2006, 09:13 AM   #5
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Primary has a single winding. No twin or multi tapping


Secondary has just a center tap.

14-0-14, 3 Amps.
Connected to a bridge to give split supply.
Can leaky caps cause this sort of recurring problem?
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Old 28th October 2006, 10:16 AM   #6
AndrewT is offline AndrewT  Scotland
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Hi,
you have only one primary, so you cannot wire it out of phase.

You have two secondary windings but they are already connected at the centre tap so, again you cannot connect the secondary out of phase.

You could have three different problems.
Faulty rectifier,
Faulty smoothing caps,
Faulty load.

Remove the load and measure the secondary voltage across each smoothing cap. It should be 20 to 21Vdc.

If one or both are low then remove the caps and measure the voltage across the + - of the rectifier, it should be 40 to 42Vdc.

If this is wrong then measure the transformer output. It should be 14Vac to 16Vac on each half winding and 28 to 32Vac across the pair of windings.

come back with some numbers.
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Old 28th October 2006, 10:18 AM   #7
djQUAN is offline djQUAN  Philippines
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did you use the same model/ brand of transformer?

could be that the transformer has poor design.

I also have a power amp with a 500VA toroid for he mian supply and a smaller EI for the fans/ DC protector and I never had those problems.
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Old 30th October 2006, 03:04 AM   #8
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Quote:
Originally posted by AndrewT
You could have three different problems.
Faulty rectifier,
Faulty smoothing caps,
Faulty load.
Cant be faulty load, since I've replaced with a different amp. So this leaves rectifier & Caps. Need to get a new transformer , rectifier & caps. This shouldnt leave room for any problems.
Thanks.


Quote:
Originally posted by djQUAN
did you use the same model/ brand of transformer?

I've used 3 different brands.
Since you've been using toroidail & EI together , I guess I can safely rule out problems due to coexistence.
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