Converting: 220 - 117V

[Tom Phillips]

… The 1484 has a ground switch on it, and I've been told to remove that switch and the death cap connected to it, in other words - the amp doesn't have a grounded power cable, so should I leave the ground switch be and use that as ground when connecting to the SD? …

I would upgrade to a grounded power cord. Proper conversion is removal of the “death cap” (OK to leave the switch itself in the chassis) and rewiring such that the ON/OFF switch and the fuse are both in the hot line. I would disconnect the convenience outlet since it’s an old non-polarized socket. I prefer not to use an amp as an extension cord anyway.

… Can I even connect to a SD like this ( 750w 750 watt 110/220 Step Up Step Down Transformer new - eBay (item 270511943921 end time Feb-06-10 11:25:37 PST) with an cable that isn't grounded?

You can use a device like that. It will work with a two prong or a grounded plug but its best to have grounded equipment.
However, I can’t find full specifications for the ST-750. Side note: The ST-750 may use an auto transformer inside. That’s fine if you are connecting it to a conventional PT. However, it you wanted isolation from the line, such as to safely use equipment that has a transformerless power supply like the Silvertone amp built into a guitar case then you would want a full isolation step down transformer.

About your 50 Hz power concern. I forgot about that. This does mean that your amp’s PT will run hotter that it would at 60Hz. I don’t know if that will be a problem or not. I don’t even see any mention of 50Hz on the Mercury Magnetics site. In fact, no specifications at all.

Tom

[J M Fahey]

Fully agree with Tom Philips and suggest again you buy a good Swedish transformer.
The one at EBay has what looks like a Schuko male plug (excellent but I don't know what you have at home) and a flimsy and unsafe 2 round pin to 2 flat pin adapter.
Besides, the price makes it highly suspect of being of cheap oriental origins.
It may even be good, but *never* better (nor equal) to a Scandinavian approved electrical apparatus.
For those who don't know it, Scandinavian countries have the toughest insulation requirements in the world, because they consider that the frozen soil (permafrost) is a very poor conductor.
They must have their very good reasons to think so.
As a similar example, Canadian Electrical Codes are the toughest in America, (I guess for similar reasons) so getting a CSA seal of approval means automatic approval in any other country of the Continent.

[Alex R]

A bit of experience on the 50Hz thing for you - your PT might run a little hotter on 50Hz, but I too would agree you should try it and see before changing it. Here in the UK I see plenty of USA PTs running fine on 50Hz. OK the Silvertone may not have too much tolerance, but give it a try and see if it gets hot to the touch.

[J M Fahey]

I can add more of the same.
I live in Argentina (220V/50Hz) and I spent the last 40 years using and repairing US/European/Japanese amps bought in Miami, NY or LA, built for the US market(60 Hz) , and used here with bulky 220/110V autotransformers, with no ill effects.
I guess that is because iron is used conservatively, at 10000 Gauss (or even less, 8000) ; while in fact it does not really saturate until 15000.
Yes, it will consume 20% higher idle current, and have 20% extra "standby" losses, but on full tilt probably there is not that much difference.
Ah! the turn-on pulse will be greater too.

[cowboy]

Thanks for all the answers! So... I ordered a SD-tranny from ebay yesterday, since it's really hard to get an SD that's approved for Sweden. I'm hoping that this solution will work, otherwise, I'm gonna let MercMag make a PT for me, but of course I hope that I can stay with the original PT as long as I can. Again, thanks for making everything a little clearer!

[J M Fahey]

it's really hard to get an SD that's approved for Sweden.

Mmmmmmmmmmmmmhhhhhh !, I guess I told you so
Toughest electrical codes in the world.
Replace the 2 wire power cable in your Silvertone with a properly grounded 3 wire type and make sure that all 3 ground connections: amp<>transformer<>wall outlet match.
They "should" but take nothing for granted, use a neon screwdriver to be sure.
Good luck.

[mfwalker1]

Hi Cowboy.
Hey I'm in Australia faced with exactly the same situation.
A mate has bought a Silvertone 1484 from the USA.
I considered trying to use the existing power transformer at 240V by removing the voltage doubler on the secondary side. See thread here:
http://music-electronics-forum.com/t17283/

In the end he bought a 500W step down transformer and the amp works great (except for the reverb - which is normal for this amp!).
No evidence of 50Hz/60Hz being an issue.

At the moment the amp is stock with the 117V cord, 0.05 cap (C31) and ground switch. I will mod this by removing the cap (c31) and providing a 3 pin USA style plug and cord. The step down TXFR provides an earth connection.

Regards,
Matt

[cowboy]

Thank you so much! That is really nice to hear, especially from someone who has actually done it. I've ordered a 750w SD tranny, but I haven't got it yet. I Will let you all know how it works out!

Thanks again.

J.T