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Rewiring Trace Elliot amp for 120V

Anonymous Fri 22 May 22:25:48 2020 No.11701753 View Reply Original Report

Quoted By: >>11701760 >>11701778 >>11701921

Got a little project in mind, I want to convert a British Super Tramp to run from UK mains to US 120V. I was able to find a service manual, and the wiring looks pretty simple. Looks to me like it uses a transformer to step down the mains to 120V? Would I be able to just bypass the transformer and use the 120V directly? Would appreciate any advice!

Anonymous

Anonymous Fri 22 May 2020 22:27:49 No.11701760 Report

Quoted By: >>11701775

>>11701753
You have less chance of frying yourself if you ask >>>/diy/

Anonymous

Anonymous Fri 22 May 2020 22:32:32 No.11701775 Report

Quoted By:

>>11701760
Thanks, anon! Sorry for posting here. Maybe a mod can prune the thread.

Anonymous

Anonymous Fri 22 May 2020 22:33:42 No.11701778 Report

Quoted By: >>11701782 >>11702403

>>11701753
are you assuming 120V from the capacitor rating?

Anonymous

Anonymous Fri 22 May 2020 22:34:55 No.11701782 Report

Quoted By: >>11701963

>>11701778
That was my assumption, I tried to find the transformer output based on the label but the design is old and I couldn't find any information for the components.

Anonymous

Anonymous Fri 22 May 2020 23:16:37 No.11701921 Report

Quoted By: >>11701963

>>11701753

You buy a 1:2 transformer, attach it somewhere in the case, and wire it between the mains switch and mains transformer. This is a lot cheaper and easier than trying to hunt down a replacement mains transformer that will produce the same output voltages with half the input voltage. I've done exactly this with British guitar amps.

Anonymous

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Anonymous Fri 22 May 2020 23:29:24 No.11701963 Report

Quoted By: >>11701976 >>11702403

>>11701782
My assumption was based on something like this, I figured if they were equal the voltage would just be divided across them. A 126V total rating seemed like a convenient number that made me guess that the output was somewhere around 120V, and anything greater was gonna be popping that fuse first. But what >>11701921 posted makes sense. Might be what I end up doing since he's had success with this. Maybe that 126V is really rated for filtering something closer to 110V.

Anonymous

Anonymous Fri 22 May 2020 23:32:49 No.11701976 Report

Quoted By: >>11702105

>>11701963
>Maybe that 126V is really rated for filtering something closer to 110V.
Wait, now I'm confusing myself. If I use a 1:2 transformer I'm now putting ~240V in, and it is getting stepped back down, but would I be risking exceeding the voltage rating of those caps since British mains is ~220V?

Anonymous

Anonymous Sat 23 May 2020 00:37:30 No.11702105 Report

Quoted By:

>>11701976
European AC is between 220v and 240v. In the US it's between 110v and 120v. It's not possible to make it exactly the same in every outlet in a country. Appliances are built to tolerate the differences.

The transformer should say either its output voltage (when given 240v) or its coil ratio. The capacitors will have the max voltage they can handle printed on them. If you check it out your going to find the max voltage is quite a bit higher than what they'd be getting from 240v into the transformer.

Anonymous

Anonymous Sat 23 May 2020 03:31:18 No.11702403 Report

Quoted By: >>11702536

>>11701778
>>11701963
the rating of the capacitors IS NOT HOW YOU DO THIS, you need to check the actual voltage and I bet is way below 110V because capacitor voltage rating always has to be higher to the actual voltage otherwise you will be running the cap too close to its limit , thats what the vaoltage on the cap means, its the limit of operation , it does not mean the operating voltage

Anonymous

Anonymous Sat 23 May 2020 05:05:34 No.11702536 Report

Quoted By:

>>11702403
Yeah, found out I ideally want a 36:0:36 center taped transformer with 120V input but they're not readily available. A 40:0:40 would probably work since that's what's in it but they're hard to come by, too, at least with a 120V input. Thanks Anons.

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