Overseas transformer

[5Trout]

Hello ! I am new on this forum, and I have built my first tube amp.
I is an deluxe head kit from stf.
I have an "overseas transformer" with 100-110-120-200-220-240 VAC
wiring options. In Sweden we have 230VAC normally.

1: Wired for 240VAC I get B+ = 347 Vdc and heater voltage 6.2 VAC

2: Wired for 220VAC I get B+ = 380 Vdc and heater voltage 6.7 VAC,
the rectifier got 5.2 VAC.

Is it harmful for the tubes to run it like example 2?

The amp runs fine wired as ex.1 but breaks up a little early, have not
played it properly wired the other way because my wife is sleeping.
Tomorrow maybe...

[Tom Phillips]

There are lots of old amps out there that run fine with the heater voltages listed in your #2. This is due to the fact that line voltages have steadily increased over the years and the old transformers were designed for the lower voltages. In the US we see line voltages marked (From oldest to newest) 110V then 115V then 117V and now 120V. However, the actual line voltage at my house is sometimes as high as 126V.

If it worries you, you can always put series resistance in the heater line to drop it down to 6.3V. Not really necessary IMHO.

Regards,
Tom

[5Trout]

Thanks for your answer, Tom.
I have not thought of those issues about US voltages...
I tried the amp today as #2, and I think I like it more that way.
The early breakup may be the result of only using half of the 12AY7.
It's an one channel amp, but I have some plans using the other half of
V1. Don't know exactly what yet, there are several things one can do...
To fun to play as is still though :)

[5Trout]

The voltages are ok now, B+ 360vdc and heater 6.3vac. :)
Mailed Hammond and asked if it was possible to connect the
372BX transformer like:
0VAC -> white
black -> jumper -> brown
230VAC -> blue/yellow

They said it's perfectly ok to do that.

Here is a picture, the camera flash makes it look like shit though...
http://user.faktiskt.se/trout/amp2.JPG