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Old 10th December 2012, 03:13 PM   #11
johnr66 is offline johnr66  United States
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I notice a lot of consumer gear operate the transformer partly into saturation. Dropping the frequency will cause this to be more of an issue. Keep tabs on the temps and be sure it isn't getting to hot.
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Old 10th December 2012, 06:29 PM   #12
JMFahey is offline JMFahey  Argentina
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Normally it *should* not be a problem.
This is confirmed by the freezing cold temperatures shown by that transformer.
As a side note, I live in 220V 50Hz Argentina, we are chock full of US amps "bought in Miami, NY or LA", US version (as in 120V_only windings / 60Hz) and that has never been a problem.
Besides, Korean stuff is usually very well made.
That transformer looks good.
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Old 11th December 2012, 07:49 AM   #13
AndrewT is online now AndrewT  Scotland
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Operating temperature is a very good indication of abuse, whether due to voltage or frequency.

Check it often and learn to "read" the abuse or not.

You may be OK.

There is an alternative:
But you need to be confident that you have the skill to do this safely.
Add extra primary turns !
Even as few a 20Turns makes a significant difference to the idle current. You can measure the primary idle current with care to avoid electrocution !
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Old 11th December 2012, 07:58 AM   #14
freax is offline freax  Australia
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Quote:
Originally Posted by bwtechguy View Post
the good news is tortech isn't far from me, but i'm unsure this will help me, i don't believe the voltage is my problem, many devices are 220-240v, and my transformer is 220v, my problem is the 60hz,

i found a article saying its a bad idea

referring to the section of the page "4 - frequency" part

Voltage and Frequency

basically he was suggesting that 60hz transformers are made smaller that the same 50hz one, and the 60hz often uses a lower grade steel lamination,
he goes on to mention:
Part of the design process for a transformer is to ensure that there are enough primary turns to prevent the steel core from saturating. This depends on the voltage and the frequency. If the frequency is reduced (and 10Hz or 16.6% makes a big difference), there are no longer sufficient turns to prevent saturation. When the core saturates, the primary winding of the tranny draws much more current from the mains than normal - not just 16% more though, it can easily exceed 100% more.
The result is that the transformer overheats, and will eventually fail.. There is actually no difference between decreasing the frequency or increasing the voltage by the same ratio.

and then shows examples on the oscilloscope...

so i don't know. any ideas?
Makes sense to me now that you mention it, its amazing what we forget over the years, but yes higher frequency transformers are smaller....

I'm surprised no one has asked you if you can measure the unloaded transformer voltages and give us an indication of its open circuit readings...

Then its dc resistance taken when all secondary windings are disconnected from the amp pcb...

Its probably because that is an enviable rats nest in there, and finding a substitue transformer for it would be next to impossible without a lot of head scratching...


-------------------------------------------------------
Option #1:
The only way I see out of this problem is to keep the transformer cooled with the fan that you've got there, possibly making a second power supply inside of the case specifically for the fan, or simply volt regulating it with a L200 vreg board off ebay and tapping into one of the AC windings which is within the range of the input voltage of the LM317...

http://www.ebay.com.au/itm/LM317-Adj...#ht_3595wt_689

Then turning the trimpot on the LM317 vreg board down so that the fan doesn't stall but keeps silent..Probably around 7-9v DC.


-------------------------------------------------------
Option #2:
This to me seems like the cheapest way out, but if the OP doesn't have confidence to do mains wiring then I suggest a different approach, and that is to simply get a power supply plug pack and a couple of chassis plugs and mount the fan inside of the case, then mount the chassis plugs and use the external power supply to keep the fan running.

I don't see any harm in letting the transformer run with a fan pointed in its general direction, does anyone else?

I of course don't take any responsibility for loss of life or injury or damage to equipment, household or family if the OP or anyone else takes my advice and that by reading the above post and or this legal disclaimer that you agree to abide by these terms.
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Last edited by freax; 11th December 2012 at 08:20 AM.
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