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Old 16th September 2006, 01:53 AM   #1
zxx123 is offline zxx123  United States
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Default Replacing Power Transformer

I found an old tube amp in my father's garage.
Everything is ok except power transformer.

I have another power transformer with the same
secondary voltage but more current.

Can I use this new part without modifying PSU circuit?

@Both of transformers have same internal resistance (impedence?)

Thanks.
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Old 16th September 2006, 02:54 AM   #2
poobah is offline poobah  United States
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Yes, the current rating is the maximum which the transformer can produce safely. The actual current flow is determined by the load on the transformer.

If this amp has been sitting there for years... it is likely that the electrolytic capacitors have failed from age (and non-use). It is also possible that this may have caused the transformer failure years ago as well.

You should not power the amp without: a, a variac to bring the voltage up very slowly and observe as you go, or b, replace all the caps first. Both would be preferable.

There should be many threads here... try "old tube amp", "reforming caps" for starters. Bringing this amp to life may not be something you wish to tackle alone.

What model and number is it?



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Old 16th September 2006, 02:58 AM   #3
Sherman is offline Sherman  United States
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The circuit will draw whatever current it needs, not what the transformer is capable of supplying. So short answer- yes it will work if the voltage ratings are the same.

Be careful though. Tube amps can contain have very high (lethal) voltages. Read the safety thread here. A simple trafo replacement shouldn't be a problem but you are likely to have to also replace any electrolytic caps and possibly many of the resistors as well.
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Old 16th September 2006, 03:17 AM   #4
poobah is offline poobah  United States
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Great minds Sherm!
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Old 16th September 2006, 03:30 PM   #5
Sherman is offline Sherman  United States
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Scary huh? First paper models of trafos etc. now this!
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Old 16th September 2006, 04:02 PM   #6
zxx123 is offline zxx123  United States
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Default ....

Thanks!
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Old 16th September 2006, 05:09 PM   #7
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assuming that you do decied to "recap" the amplifier (I highly recommend you do), if its your first tube job, don't spend alot of money on expensive capacitors. Designer capacitors get expensive quickly.


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