Hi Guys,
I have inherited a Stromberg Carlson 5A26, missing its power transformer.
Can anyone help with supplier information or the technical specs for a 240V input transformer.
I think it should be 300 0 300 with 6.3V and a separate 5V for the rectifier 5Y3G heater.
I can find a similar transformer used in a Fender Champ guitar amp also used with a 5Y3G
Hammond 010020
input 230, 240 50 cycle and 120 60 cycle
325 0 325 or 275 0 275 either at 100ma
5v 3a
6.3c 2.25a
Any comment would be gratefully appreciated.
Regards Jim Stringer

The Fender transformer would be ideal in all respects.
Hope it will physically fit.
JJ

Thanks JJ The last time I visited valve theory was in the 1960s when doing electrical engineering HNC. I new it would be useful one day!
Rgds Jim

According to the schematic the secondary H.T. to the rectifier plates is 230 0 230V & the rectified H.T. is 220V

Hope this is of some help.

Yes, if the radio had a speaker field coil that secondary voltage would be appropriate, a bit high otherwise.
You might find you need to drop the B+ a bit. Best way is a resistor from 5Y3 cathode to 1st filter. This is kinder to the rectifier and the filter and reduces hum, but you need a lower value resistor due to the peak current.
Start with about 47 ohms 10 watts and see what you get.

Yes, I did not study the circuit, but the output valve will handle 300 odd volts easily.
Otherwise it’s fairly easy to get rid of 30 odd volts with a bit of resistance, as Ian has suggested.
And of course select the 240v primary option.
As I believe the Aus standard is now 230v. (Where do you find that!).
JJ

AS 60038 was brought in to alter the nominal voltage and tolerances - a worthless and completely nonsensical piece of red tape given that 240V still comes out of the GPO.

Most electrical accessories are still rated at 250V/440V as appropriate and as the tolerances actually exceed this, I doubt the ratings will be lowered any time soon.

Thanks for the info, I have ordered an R-Core R80-47 transformer which gives me
250-0-250 at 150MA
0-6.3 at 3.5A
0-5 at 2A
That shoud do the trick with less messing about!

My supply voltage in OZ is 240V no matter what the standard says, I think it says 230V within 10 percent.

Also the place you will find 240 nominal supply is the USA domestic supply, every house is supplied with 120-0-120 and for water heaters and aircon they connect across both 120 circuits giving 240V and a bit more omph. If you look on their breaker panels you will see double width breakers that clip into both supply rails.

Again thanks for the advice.
My Regards
Jim

The new AusNet transformer here was set at 240V. The old one was damaged when worked on (seals) & starting to creep above 250V. By the amount of dirt the leaking oil was gluing to the insulators, there must have been considerable leakage. Have a photo of it.

Interesting as to how they get 120 - 0 -120 to 240V as 240 + 240 does not add up to 480 as its a vector sum & cos theta gets involved, AC can be very strange at times. Had a phase fault in a 1929 Lyric 70 series, at one point. AC filaments: That was quite fascinating, with a corrosion cause.

A series resistor before the first filter will act as a choke input filter and lower the volts as will reducing the capacity of the first filter cap. Panel mounted resistors are good, mounted on a metal side.

This is also where transformers with tapped primaries were good. +/- 20% is the accepted variance in "B" voltage.

Marc

Interesting as to how they get 120 - 0 -120 to 240V as 240 + 240 does not add up to 480 as its a vector sum & cos theta gets involved

Not certain, but I think the US system is 2 phase, not 3 as is here, so it appears as 240V phase to phase, centre tapped.

Perhaps one of our US friends could confirm?

Harold

US household services are indeed 120V-0V-120V centre-tapped. So each 'phase' is 180 degrees out of phase, rather than 120 degrees as is here.

They use 240V rarely but as mentioned, heavy appliances like clothes dryers (think Speed Queen) run on 240V and they use the same models as they send out here for our laundromats.

That should solve it. However, three phase is more efficient to generate. Even car alternators are 3 phase. That of course does not mean it cannot be converted. There is a setup near here taking 3 phase to single wire SWER & I have seen one putting out 12 phases for tubes with 250 Amp heater / filaments.

Hi Stringer .
All a bit late for you now I recently acquired an 5A26 Stongberg Carlson chassis . It's power transformer appears to be good. I measured the primary winding and it is ok . I have meggered to ground and it's ok.
If you want it I will send the chassis to you . I have used the tuning gang off it and I intended to use the choke however the choke must have died due to corrosion or some such cause as it measured 300k ohms.
If you need it send me you address my email is open.
Regards Jimb