Rob Rob's BlackVibe Micro power transformer for 100v Japan?

[takayuki]

Dudes,

I'd like to build a RR BlackVibe but want to get the power transformer right.

Blackvibe

RR763 BLACKVIBE Guitar Tube Amplifier

robrobinette.com

Here is RR's recommended PT but this is for 120v.

I recommend the use of a Princeton Reverb chassis and Classictone 40-18027 Princeton Reverb power transformer. The 40-18027 supports 120v and 240v mains and has two high voltage windings. We'll use the 275-0-275v 100ma red-white high voltage leads which are perfect for the Blackvibe Micro. The entire amp uses only 24ma at idle. The power transformer has a 6.3v center tap so an artificial center tap is not needed. We connect the 6.3v center tap to the hot side of the power tube cathode resistor to elevate its ground reference to reduce heater hum. If you need a stand-up transformer the Classictone 40-18085 is perfect.

What should I use for Japan/100v?

Thanks

 

[wangdaning]

I think your best bet is to get something from Japan. Try to locate transformer suppliers there and give then the secondaries you require. Most well known brands will only have primaries for US/EU/UK. So, 120 will be about as low as they go, which will cause you to have lower output on the secondaries. I would imagine there are people who make transformers there for the hifi crowd, if not for tube amps.

 

[owlexifry]

100V isn't that far from 120V.
it would just mean that the secondary high voltage windings have a slightly lower voltage than advertised.

not sure how much this would matter for the amp circuit in mind.... some component value adjustments may be required (B+ dropping resistors etc.)

 

[wangdaning]

Yeah, I would mainly be worried about the heaters.

 

[sds1]

Get Hammond 291AEX

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www.hammfg.com

Has the 100V primary option and matches Rob's spec for 275-0-275 @ 100mA.

Will fit the Princeton Reverb chassis.

 

[takayuki]

Thanks for the replies owlexifry, wangdaning and sds1.

I found the 291aex here: https://www.digikey.jp/en/products/detail/hammond-manufacturing/291AEX/2357977

about $120

I've just started the journey, don't know what I'm doing, so I think I'll also head to the elec parts store in town with the schematic and see what they've got.

 

[takayuki]

Another noob question...

If I go with the solid state rectifier option, the power supply is a 125-0-125. Here's the schematic from Rob R's awesome site: https://robrobinette.com/images/Gui...IBE/RR763_BLACKVIBE_MICRO_SS_Layout_small.png

Which brings me back to which PT I should get?

I found this 369ax at digikey japan. I need a 100v primary and this has it. Would this PT work?:

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www.hammondmfg.com

thanks for any assistance here.

 

[wangdaning]

That PT hits the specs needed based on the layout, yes. It seems to be a stand up transformer though, I think you need to think about chassis as well. Wouldn't you need a laydown transformer?

 

[2L man]

It has lots of spare current for micro amps! If it fit you can use it. Perhaps filament voltage stay bit too high but that is easy to drop installing series resistors. They can be installed in between filament feed wires and insulated with heat shrink tubing. But their value is possible to define only when you power up the amp and possibly very low value resistances are not easy to find nearby?

Remember to connect both primary coils parallel!