Secondaries in series - CT?

[fyzygy]

I have an old HP oscilloscope power transformer with dual 104v secondaries (among others). I intend to wire them in series for 208v. My question is, can the link between the two secondaries be used as a 'centre tap' connection - which I can run to ground? Or would that put me back where I started, i.e., with 104v?

[!]

Are they both the same wire gauge? If not, current will be limited by the lesser (higher gauge) of the two.

Yes the link could be a center tap ground, assuming you want +/-104V rails, not a 208V positive rail and ground on the other end of the second winding.

[fyzygy]

So, a tube rectifier across the series-connected secondaries would yield (roughly) 104V not 208V?

[AudioSan]

is this gonna be single rail or dual rail PS?
i guess you are looking for single rail. in that case. it is not a centertap. but a series connection of the 2 sec. and can NOT run it to ground.
if it is dual rail with one rectifier, then run the centertap to ground.

[fyzygy]

I was hoping to get around +200vdc (single rail) for a tube circuit, preferably tube rectified. the mains transformer secondaries are 6.3vdc, 6.3vdc, 31vct, 104vdc, 104vdc, 145vdc. the 104vdc secondaries were used to provide a dual-rail supply in an old oscilloscope. i wonder whether wiring the 145vdc and 31vct secondaries in series, instead, would get me in the ballpark of 200vdc?

[AudioSan]

you can not use ct's in series. you can however use the 2 104v in series to get 208v (single rail)
but do NOT centertap it to ground. that will be a short.

[AndrewT]

All the secondaries should all be isolated from the Primary/ies

Have you checked this thoroughly?

Two isolated secondaries can be connected together. Either in series or in parallel. But, if in parallel then the secondaries must be identical, i.e. exactly the same number of turns.

Once you have a pair of isolated secondaries connected together, you decide which tapping is connected to which reference voltage.

BTW,
secondaries and primaries are rated in Vac not Vdc.

When you rectify and smooth the secondary output the secondary voltage is given very approximately by Vdc ~ sqrt(2) * Vac.