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Audio Output Transformers

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Davek0974
(@davek0974)
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Not seen this before, am i right this OPT is a single-ended one but with ultra-linear winding and also being used as a PSU choke?

Screenshot 2020 12 11 at 07.29.58
 
Posted : 11/12/2020 7:31 am
Nuvistor
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@davek0974

Quite a standard circuit, the ripple on the HT line will be through both sections of the windings but opposing each other, less ripple in the audio output stage to the speaker.

Saves a larger reservoir capacitor.

From Radio Servicing pocket book, J.P. Hawkwer.

4D5962CD 4841 435A BAA1 B7BD108E9468

Frank

 
Posted : 11/12/2020 9:37 am
Davek0974
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Posted by: @nuvistor

@davek0974

Quite a standard circuit, the ripple on the HT line will be through both sections of the windings but opposing each other, less ripple in the audio output stage to the speaker.

Saves a larger reservoir capacitor.

From Radio Servicing pocket book, J.P. Hawkwer.

4D5962CD 4841 435A BAA1 B7BD108E9468

Thanks, thats interesting, was i right that the other winding is for U/L tapping??

 
Posted : 11/12/2020 10:00 am
Nuvistor
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@davek0974

To be honest I had not noticed the winding for the screen grid, I shouldn’t  post first thing in a morning, or perhaps not at all.

Is it a Philips  circuit? If you have a make and model number I will try to find out more, unless some one else answers the question.

Frank

 
Posted : 11/12/2020 10:43 am
Davek0974
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Posted by: @nuvistor

@davek0974

To be honest I had not noticed the winding for the screen grid, I shouldn’t  post first thing in a morning, or perhaps not at all.

Is it a Philips  circuit? If you have a make and model number I will try to find out more, unless some one else answers the question.

Screenshot 2020 12 11 at 10.44.22

Lol, its from a Cossor tape recorder, full story - I got a HT and OPT from ebay - i wanted the EZ80 really and it was a good price so....

Looking at the OPT it had loads of taps so very confusing, luckily the guy had the diagram too, no idea if i'll ever use the OPT but an extra in the box is never a bad thing right??  🙂 

 
Posted : 11/12/2020 10:47 am
Nuvistor
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@davek0974
I don’t know if it’s for UL type performance or if they felt it was required due to the circuit being used for the Bias oscillator in the recorder. It’s a Philips circuit, EL3515 and EL3541 are the same machines.

 

Frank

 
Posted : 11/12/2020 11:10 am
Davek0974
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@nuvistor even thats interesting as there is no way of disconnecting the speaker if they are multi-purposing the output valve ?

Amazing circuits.

 
Posted : 11/12/2020 12:21 pm
Nuvistor
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@davek0974

The osc coil S17 will resonate around 50-60Khz, doubt the output transformer will pass much to the speaker.

Philips came up with some different circuits that can confuse, they do me at times, but they usually work extremely well.

 

Frank

 
Posted : 11/12/2020 1:03 pm
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