Hi all, and thanks in advance for any guidance you can give. I just received a Triode VP-300BD tube amp from someone in the US, but it was configured as a 100V unit. Opening it up, I see the 100V transformer leads wired directly to the switch, and there are 120V leads that are not connected. Would switching to 120V be as simple as disconnecting and sealing the 100V leads and then connecting the 120V leads to the power switch? I suppose I would just need to bias the amp after, but is it as easy as that?
Unfortunately the manufacturer is neither providing a manual nor support for this modification. At worst case scenario I have a good step down transformer, but this seems like an easy mod considering the transformer has 120V windings.
Thanks.
iCloud
Unfortunately the manufacturer is neither providing a manual nor support for this modification. At worst case scenario I have a good step down transformer, but this seems like an easy mod considering the transformer has 120V windings.
Thanks.
iCloud
An externally hosted image should be here but it was not working when we last tested it.
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If it has the 120V primary winding(s), yes just reconnect the wires. In your amp, it may have two (a pair of) primary windings. Check how the 100V taps are connected and duplicate. It likely is just a parallel pair. I would make sure the filament voltages are within spec afterward. Also re bias the amp to account for house voltage difference.
Ok, great, that’s what I thought but wanted to hear from folks who obviously know more than me! I’ll report back once I get it dialed in over the coming day or two.
There should be no need to rebias the amplifier, since the point of changing the transformer connections
is to get the right voltage on the secondary. You can still check it, though.
is to get the right voltage on the secondary. You can still check it, though.
No, it certainly has 120V leads as seen in the pic/link in my original post. And the kit versions Victor sells do come in 120V versions, it’s the same transformer.
And to answer and earlier post, yes there are two leads for each 100V and 120V. Currently both leads for the 100V are joined and soldered to the same side of the power switch. Should be a very easy swap.
And to answer and earlier post, yes there are two leads for each 100V and 120V. Currently both leads for the 100V are joined and soldered to the same side of the power switch. Should be a very easy swap.
It sounds like you know what you are doing. However, it would be worth checking a couple of things. (1) Be sure that it actually is wired to the 100V taps right now. Markings often don't line up with exactly with wires. Use measurements to be sure. (2) Don't assume that using the 100V taps was an error. If it's an old amp modern mains voltages could be making secondary voltages higher than design. The previous owner could have measured this and made an informed decision to pick the lesser evil.
With ref to point #2 reply#8, secondary voltages would climb to still higher and dangerous territory if 120/125 volts supply from the wall socket is connected to 100 volts primary. 120 volts primary would be much better.
Regards,
Regards,
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I was able to swap the leads tonight, and measured the amp. Powered it up and it sounds decent. It came with some pretty poor quality 300B tubes, so I’m itching to roll them but new ones don’t arrive til tmw. But overall, sounds great considering what I invested into the amp.
Thank you for all your help - this truly is a great community.
Thank you for all your help - this truly is a great community.
Thanks for pointing out the error in my logic.
OK, it sounds good, but did you actually measure anything?
OK, it sounds good, but did you actually measure anything?
Yes I did, the one page of the manual Victor did give me was checking the voltage for the 300B grid so I could bias it using the variable resistors. Everything seemed to check out that way.
JFYI: The US is 120V nominal. The *only* place in the world using 100V power line is parts of Japan. Japan is big Hi-Fi, so there is a lot of 100V Japan-market gear. And some of it gets into the US. But if not converted to 120V it won't run for long on US wall power.
If the US owner never used it in the US, then it may be 100V. Or if a conversion transformer was used. But if it worked many hours on straight US 120V power, then it likely is not configured for 100V.