Ampeg SVT-3 Pro -- Smoking Toroidal

[Steve Conner]

This forum has a known problem, he keeps posting information that is plain wrong. The transformers are not "designed for 100V".

[soundguruman]

This forum has a known problem, he keeps posting information that is plain wrong. The transformers are not "designed for 100V".

Did you take the transformer out, and read the label?
I think the last one I worked on was labeled 100-115 VAC...on the factory label.
Therefore, in that case it WAS designed to run on 100VAC.

Yes there are many products made for 100 volts, and they are exported to use at 120VAC.
Example is Nakamichi tape decks. And Digitech effects pedals.
It does run at 120, but the life is greatly shortened. Runs too hot you see.
When you look more closely, you will see that what I am saying is not so crazy, but true.
Although at first it's hard to accept the fact.
Kustom, Hartke, etc..all have the same problems.

[Dave Curtis, dB AudioTech]

He did say "IMHO", and we all know what his "humble" opinions mean...

[Enzo]

WHy not look at the schematic? The SVT3 Pro power transformer has a dual primary. The primaries are 120v windings with 100v taps. You can run it on 100v by changing the wiring over to the 100v taps as outlined in the drawings.

SO yes indeed you can run the amp on 100v if you change the wiring. However, the claim guruman makes is that the amp is designed for 100v and we use it on 120v causing stress. Not so. The 120v taps make the secondary voltages the exact same as the 100v taps when they are fed 100v.

[Steve Conner]

So, as I suspected, it was designed for 100, 120, 200 or 240V.

Once upon a time, when Japan made cheap, nasty electronics, they may well have exported gear to the US without bothering to change it from 100V to 120V. If you live on the west coast of the US, you might also come across unofficial imports that were actually intended for the Japanese domestic market.

I was once burnt (literally!) by a SMPS that was designed for 220V. It exploded when I used it on our 240V line voltage. But this was a niche product from a small company who went out of business shortly after.

PS: South Korea uses 110V, not 100.

[soundguruman]

WHy not look at the schematic? The SVT3 Pro power transformer has a dual primary. The primaries are 120v windings with 100v taps. You can run it on 100v by changing the wiring over to the 100v taps as outlined in the drawings.

SO yes indeed you can run the amp on 100v if you change the wiring. However, the claim guruman makes is that the amp is designed for 100v and we use it on 120v causing stress. Not so. The 120v taps make the secondary voltages the exact same as the 100v taps when they are fed 100v.

The ones I have been looking at do not have multiple primaries. Only ONE winding.
Maybe the schematic shows a tranny with taps, but the ones I am seeing do not.
Perhaps mystery amp manufacturer has an international transformer, why don't you buy one from them???
I know why. They don't sell critical parts. They don't sell transformers.
Once your tranny blows, no parts, no support. Disposable amplifier.

[J M Fahey]

The ones I have been looking at do not have multiple primaries. Only ONE winding.

Simply there is not such an SVT Pro. Period.
Even less "many" as you imply by writing "the oneS"

[gtrmann]

Did you remove all the secondary windings and put the tranny on a load lamp ? I have 4 or 5 of these amps come through my shop every year, I have never seen a transformer problem with them. I have seen the bias controls open up due to oxidation, taking out the power amp....that might be a Florida thing though..