Parmeko model 9000/65B Mains Transformer - UK Vintage Radio Repair and Restoration Discussion Forum

Dave757 · 3rd Jul 2020, 12:17 pm

Hi,

I have one of the above transformers and would welcome
some advice on its use.

It has three separate 6.3V windings, 1 amp, 2 amp, and 3 amp.
I would like to parallel the 2 amp and 3 amp windings as I need a 3.5A
heater supply, but there is no indication of the start of the windings,
so what is the best way of going about it?

Also, the HT supply is rated at 0.1A DC (CD). Does the CD perhaps mean
continuous duty? If it is, what would the intermittent rating be?

I am wary of using this as the power requirement for the receiver I
am thinking of using it with ( A Rees Mace CAT) is .135A.

Kind regards

Dave

John_BS · 3rd Jul 2020, 1:09 pm

If you wire the winding in series you can then easily detemine the phases:

0V out: the two starts are connected
12.6V out: you have a finish connected to a start.

Re intermittent rating: if it's quite a large transformer, it will have a reasonably large thermal mass, so 35% overload would probably be fine for 10 to 20 minutes or so.

John

Dave757 · 3rd Jul 2020, 1:42 pm

Hi John,

Many thanks for that, I should have thought a bit harder about it.

Re the HT, although it is a very hefty transformer, I was thinking I
might get away with it as the radio has a 2W audio output, and I
would be lucky to use a fraction of that into headphones.
Then the grey cells kicked in momentarily, and I realised that if I turned
the volume down to nothing, it might save about 10mA at 245VDC.
Ah well!

Kind regards
Dave

snowman_al · 3rd Jul 2020, 1:55 pm

Quote:

Originally Posted by Dave757

Re the HT, although it is a very hefty transformer, I was thinking I
might get away with it as the radio has a 2W audio output, and I
would be lucky to use a fraction of that into headphones.
Then the grey cells kicked in momentarily, and I realised that if I turned
the volume down to nothing, it might save about 10mA at 245VDC.
Ah well!

Err, not if the amp is operating in Class A.
I do not know the circuit, but if it has a single output valve (6CH6?) then it draws (virtually) the same current regardless of volume.

Dave757 · 4th Jul 2020, 10:57 am

Hi Snowman,

Just shows how much I don't know about amplifiers!

I'd already decided that I didn't like the idea of drawing
more than the rated current. so as I still have work to
do on the set anyway, I will sort out a different HT source.

Many thanks for your reply

Kind regards
Dave

3rd Jul 2020, 12:17 pm	#1
Dave757 Heptode Join Date: Apr 2009 Location: Scratby, Norfolk, UK. Posts: 650	Parmeko model 9000/65B Mains Transformer Hi, I have one of the above transformers and would welcome some advice on its use. It has three separate 6.3V windings, 1 amp, 2 amp, and 3 amp. I would like to parallel the 2 amp and 3 amp windings as I need a 3.5A heater supply, but there is no indication of the start of the windings, so what is the best way of going about it? Also, the HT supply is rated at 0.1A DC (CD). Does the CD perhaps mean continuous duty? If it is, what would the intermittent rating be? I am wary of using this as the power requirement for the receiver I am thinking of using it with ( A Rees Mace CAT) is .135A. Kind regards Dave

3rd Jul 2020, 1:09 pm	#2
John_BS Octode Join Date: Dec 2008 Location: Wincanton, Somerset, UK. Posts: 1,780	Re: Parmeko model 9000/65B Mains Transformer If you wire the winding in series you can then easily detemine the phases: 0V out: the two starts are connected 12.6V out: you have a finish connected to a start. Re intermittent rating: if it's quite a large transformer, it will have a reasonably large thermal mass, so 35% overload would probably be fine for 10 to 20 minutes or so. John

3rd Jul 2020, 1:42 pm	#3
Dave757 Heptode Join Date: Apr 2009 Location: Scratby, Norfolk, UK. Posts: 650	Re: Parmeko model 9000/65B Mains Transformer Hi John, Many thanks for that, I should have thought a bit harder about it. Re the HT, although it is a very hefty transformer, I was thinking I might get away with it as the radio has a 2W audio output, and I would be lucky to use a fraction of that into headphones. Then the grey cells kicked in momentarily, and I realised that if I turned the volume down to nothing, it might save about 10mA at 245VDC. Ah well! Kind regards Dave

4th Jul 2020, 10:57 am	#5
Dave757 Heptode Join Date: Apr 2009 Location: Scratby, Norfolk, UK. Posts: 650	Re: Parmeko model 9000/65B Mains Transformer Hi Snowman, Just shows how much I don't know about amplifiers! I'd already decided that I didn't like the idea of drawing more than the rated current. so as I still have work to do on the set anyway, I will sort out a different HT source. Many thanks for your reply Kind regards Dave