Guitar amp Power transformer swap

[Trench Recordings]

Hi All,
I have a VHT special 6 guitar amp that is set for 230V primary and I would like to replace the power transformer for 120V primary for North America. Seems like specs show at 275V @ 100mA (no center tap); 6.3V @ 1.25A.

Did some power transformer searching and I came up with a Hammond 290XXA - 260V @ 170mA; 6.3V @ 3A. Will this be ok? Or should I step up to 300V? Hammond doesn’t have a 275V that I can find. My line voltage in the studio is a little high so probably will be fine.

 

[Tubetec]

I think it should be ok , what might be worth checking is chassis space , mounting style etc

The fractional difference in HT voltage wont make any difference , mounting the new mains Tx in the wrong plane could increase hum a lot .

 

[Trench Recordings]

Thank you, I will keep that in mind

 

[Whoops]

Hi,
can't you find someone locally that can Rewind that transformer primary for 120V?
It's just a matter of having the primary with Half the turns it has at the moment winded with wire double the size.

I have transformers re-winded all the time over here from 120 primary to 240v primary, a local re-wind shop does that for 30€.

Best regards and good luck

 

[john12ax7]

Have you checked the current transformer? Often times there will be dual primaries that can simply be rewired internally.

 

[Whoops]

Have you checked the current transformer? Often times there will be dual primaries that can simply be rewired internally.

yes, thats a classic also

 

[Trench Recordings]

Hmm interesting idea about rewinding the transformer. I don’t know anyone that does that but I will look into it. Only two wires coming off the primary so no way to rewire it.

Thanks

 

[Trench Recordings]

Well you just opened a can of worms for me and I'm gonna try rewinding this myself . Learning alot about transformers. Anyways I have the transformer apart and I counted 1072 turns on the primary. Looks like 30 awg or smaller. I'm going to rewind with 26 awg 560 turns and see what happens. Maybe 600 turns and subtract from there.

Amp says input power is 33 watts

 

[Whoops]

Anyways I have the transformer apart and I counted 1072 turns on the primary. Looks like 30 awg or smaller.

You need to wire it will wire that is double the thickness of the previous primary.
You want the new copper windings to occupy the same area as the previous primary with double the turns.
The area that the copper occupies has to be the same independently of the number of turns.

Good luck with winding it. Depending on the transformer construction it might not be hard