[viggen]

Hi.

I have an opportunity to buy a tube rectified EL84 based tube amp with 4 wpc.  It has Tango transformers and made in Japan.  So, it has 100v and AFAIK 60hz power input. 

Seller says he could install a resistor to step down in lieu of a step down transformer. 

Is this safe with a tube amp?  Seller says only downside is the resistor will produce some heat.

Thanks.

[FullRangeMan]

Hi.

I have an opportunity to buy a tube rectified EL84 based tube amp with 4 wpc.  It has Tango transformers and made in Japan.  So, it has 100v and AFAIK 60hz power input. 

Seller says he could install a resistor to step down in lieu of a step down transformer. 

Is this safe with a tube amp?  Seller says only downside is the resistor will produce some heat.

Thanks.

Japan have both 50Hz and 60Hz.
Seller says he could install a resistor to step down in lieu of a step down transformer. 
If the resistor goes out the amp will receive full 120V.
The correct is rewind the power transformer primary wind to 120V using the original core, its not a rocket science job.

[viggen]

I think the resistor is installed between IEC and whatever connects to the IEC, a transformer?

Something like what's talked about here:

https://www.tapeheads.net/threads/running-japanese-tape-decks-100v-on-north-american-120v.57947/#post-734321

It's a no no with tape decks according to this site.

[FullRangeMan]

I think the resistor is installed between IEC and whatever connects to the IEC, a transformer?
Normally would be in this position.

[JakeJ]

I don't like it.  No sir, I don't like it one bit.



I would not feel safe about operating a tube amp like this.

[opnly bafld]

If you have a proper US voltage transformer and voltages are high changing a resistor in the power supply works.
With a 100 volt transformer I would want to lower the voltage before the amp.
There are a number of products designed to run Japanese voltage in the US.

My wall voltage regularly runs at 124v, so to keep the heater/filament voltage correct I use a bucking transformer with an older 117v Ampex 6973 amplifier. 

[viggen]

I just don't want to connect to another device hence trying to avoid using a step down transformer hence the seller suggested the resistor solution. 

I guess unless we re wound the transformer, there's no way to avoid an external device to safely step down to 100v.

It's such a lovely looking amp too...

[JakeJ]

Just curious, why no love for a step-down?

[viggen]

Another device taking up space, harder to minimize wires... harder to cable swap... potential of using the wrong outlet... harder to resale down the road. I know I avoid buying something that requires a step down.

[SET Man]

Hey!

   Wait! A power resistor at the 120V input to step down to 100V? I've never heard anyone doing that. First off you'll need a very high power resistor to do that and likely have to deal with heat.
 
    Honestly the easiest way and safer way is to get a good step-down 120V-100V transformer. Just make sure is rated at least twice the max power consumption of the amp.

   Another way to look at is to see if the the main power transformer can be rewired to 120V. Many main power transformers have multiple voltage input, even though they don't say it on the outside of the components.

[FullRangeMan]

Many main power transformers have multiple voltage input, even though they don't say it on the outside of the components.

Good point 

[FullRangeMan]

I just don't want to connect to another device hence trying to avoid using a step down transformer hence the seller suggested the resistor solution. 

I guess unless we re wound the transformer, there's no way to avoid an external device to safely step down to 100v.

It's such a lovely looking amp too...

Wow these are quality irons. This Tango trafo can be rewind easy.
If the amp are low priced and was made with Hard Wiring Poin to Point it worth the hassle.

[viggen]

I will check with seller if he could perform rewiring if that's possible or whether he could rewound.

Seller is an EE and does refurbs.

I found him trying to find someone local to fix another amp.

If he can't do either, I'd sadly give back this beauty of an amp.

Does one need special equipment or skill to rewound?  Not sure if it's economical to do this?

[FullRangeMan]

Does one need special equipment or skill to rewound?
Previous experience and care are required.
https://www.youtube.com/results?search_query=rewind+transformer