Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jase128 on April 16, 2017, 04:05:24 pm

Title: transformer help please
Post by: jase128 on April 16, 2017, 04:05:24 pm

Hi
Hi All,

I have just bench tested a Hammond 291aex transformer before fitting.
It has a dual supply 110v or 240 v and outputs of 650, 550 , 6.3 and 5v  all output voltages are ok.

It has a copper strip/band around the outside which I believe is to reduce hum?? but when I power it up Im getting voltage between the strip and ground - with 240v supplying it read 110v from copper to ground and with 110v supplied it reads 70v to ground?

is this ok?

many thanks for any help

Jason

Title: Re: transformer help please
Post by: sluckey on April 16, 2017, 04:43:36 pm

Transformer is just sitting on the bench? Nothing connected to it except the primary?

You're putting one meter lead on the copper strip but what is the other meter lead connected to? IOW, what are you calling ground? The green wire in the power cord?

This is probably nothing to worry about.

Title: Re: transformer help please
Post by: jase128 on April 16, 2017, 04:56:18 pm

thanks for the reply,

yes Sluckey one end of the dmm is on the copper and the other on the earth lead! nothing else connected up just in terminals

thanks


Jason

Title: Re: transformer help please
Post by: sluckey on April 16, 2017, 05:38:17 pm

That bogus voltage should disappear when you mount the PT on a chassis, connect the green power cord wire to chassis, and begin wiring everything up.

Title: Re: transformer help please
Post by: jase128 on April 16, 2017, 06:11:56 pm

ok will do, thanks again for your time


Jase