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Marantz 8b from Japan

C

cray

New Member
I just ordered one from Japan and I’m expecting it to arrive shortly. I know Japanese voltage is 100v but would I be able to run it in the US with average of 120 volts? I’ve been told “it shouldn’t matter that much” and that it “should be ok within that range”. This coming from a tube gear expert… but I don’t like the lack of certainty in those words.
Any non passive aggressive opinions are greatly appreciated
Thanks
 
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I wouldn't plug it into 120 volts if it's wired for 100 volts. One thing it will do is raise the heater voltages too high for the tubes. If it does in fact have 100 volt primaries on the power transformer, you can buy a 100v to 120v converter.
 
The 120V version run the PT quit hard. It's getting toasty after long period of listening.
I would not chance it. If you have a variac you could power it with 100V, and measure the heater AC voltage, to measure what AC line gives you the 6.3VAC expected (with tubes so under load).
Then you'll know if the PT was indeed for the Japanese line voltage or not.
 
Brice said:
The 120V version run the PT quit hard. It's getting toasty after long period of listening.
I would not chance it. If you have a variac you could power it with 100V, and measure the heater AC voltage, to measure what AC line gives you the 6.3VAC expected (with tubes so under load).
Then you'll know if the PT was indeed for the Japanese line voltage or not.
Click to expand...
That's it exactly. If it has the accessory socket, I think you can monitor the heater voltage there as it's spooled up on a Variac.
 
I wonder if it has multiple primaries? I've heard some PTs had optional primary leads tucked away inside side bells.
 
grindfix said:
I wonder if it has multiple primaries? I've heard some PTs had optional primary leads tucked away inside side bells.
Click to expand...
Here's a partial skiz screenshot of a variant from Ampslab, voltages not specified. I've also seen split primaries for 115/230 VAC and a single 115 VAC primary.
Screenshot_20220410-204840.png
 
The Marantz has potted transformers, but they may have made special PT5-x for the Japanese market.
 

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Limited experience here but I haven't seen commercially built equipment with voltage selector plug/switch prior to 1971ish. Would be a blessing for OP if his amp is the one that has it.
 
If it indeed has a 100V primary, it is close enough to work, but not close enough to be reliable. Once you figure out what you actually have, then the next steps can be proposed. Getting a tube Marantz is exciting news in any case!
 
Whoever told you it doesn't matter is not competent to give advice on this subject. You can't run a product designed for 100VAC on 120-125VAC. The power transformer will likely overheat, tubes will operate above their filament ratings, and various capacitors may be pushed above their limits. If this amplifier only has a 100VAC primary winding, you should plan to add a bucking transformer into your system or replace the transformer in the amp.

Jack
 
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