Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: smackoj on October 01, 2014, 07:57:43 am
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Hi amigos; long time no post but I'm still kickin' PTL. I have a friend in Norway who wants to buy a vintage Newcomb Pathfinder (4-EL84 model with 2 preamp tube and one 5U4 recto) amp and use it in Norway. I'm not sure if changing out the PT is the best idea? This PA amp is in 9+ cosmetic condition and I kind of hate to start making major changes but it won't operate on 240 volts. What say the best and brightest tube amp minds that haunt this corner of the universe?
gracias hermanos,
smack jack :icon_biggrin:
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If you don't want to change the PT then you'll need a stepdown transformer. This is really the easiest solution. No need to mess with the amp. Just plug the stepdown transformer into the wall and plug the amp into the stepdown transformer.
http://www.hammondmfg.com/172.htm (http://www.hammondmfg.com/172.htm)
http://www.hammondmfg.com/289T.htm (http://www.hammondmfg.com/289T.htm)
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changing the PT is likely your only option. your PT is probably rated for 60Hz service: EU is 50HZ. it will burn up eventually even assuming you're using 115V/230V step-down. if the device has a factory label that states 120V 50/60Hz printed on it somewhere, then you're OK, otherwise assume it's 60Hz only.
--pete
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I'm not sure about this, but seems to me that PRR some time ago told that a 60Hz transformer can be used with 50Hz line without big problems
I hope that PRR can confirm or deny what I remember
If I remember true, I think that a step down autotransformer will do the job instead of using a more expensive traditional step down transformer
Franco
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Thank you amigos. The gent in Norway is going to give it a go with a Step-down transformer. I would still be interested to hear more info about the
50hz vs 60hz question on the step downer?
adios for now, smacko
:icon_biggrin:
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> told that a 60Hz transformer can be used with 50Hz line without big problems
Other way.
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Hi PRR
Other way
Ahem .... :dontknow:
Please, what do you mean :w2:
Franco
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50Hz transformer, 60Hz line.
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Ah ! OK
GRAZIE HotBluePlates
Franco
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Skip the theory. Think this way.
Say you need an output transformer.
Say you need it to be good to 20Hz.
Or say you need it to be good to 100Hz.
Which is bigger?
Certainly the one good for 20Hz.
Power transformers are similar. Lower frequency needs a bigger transformer.
Now say you live in the USA/Canada where power is always 60Hz. You will design the power transformer for *just* 60Hz. That's all the old classic Fenders sold to the home market.
A 50Hz transformer will be about 20% bigger. And roughly 20% more cost. Fender would not pay that cost for a USA/Can-only transformer.
When you take the 60Hz transformer to a place with 50Hz power, even after you adjust the voltage, you still have the too-low frequency. The transformer runs inefficiently, over-heats, burns-up. You need what Fender called an "Export" transformer, what the rest of the world calls a "normal" transformer. This will either be 20% heavier or made with 20% better iron (and also have the several connections for the many voltages around the world).
But it depends. Today many transformers are "global", meaning they are designed for 50Hz (60Hz works fine) and have dual primaries to cover the two main voltage ranges. Also VERY large transformers (over 200VA) *tend* to have ample inductance, so a 60Hz design may just run a little warmer on 50Hz. OTOH very small cheap 60hz iron is already strained to handle 60Hz and may die in minutes on 50Hz.
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Thanks for the explanation PRR
Franco