Philips car radio transistor output

[vindi93]

hi i have a philips n4g93vt hybrid car radio. the ouput valve is an ef98.
i have the circuit diagram however what i dont have is the second part of the radio that contains the transistor. the transistor is an oc26 on the circuit diagram it shows 2 transformers i could possible build the final output stage. However how do i work out what transformers i need??

[ronbryan]

There is some guidance in "Mullard Manual of Transistor Circuits" detailing a single-ended OC26 output stage for car radio. The section starts on page 137 of the "Class A Output Stages" Chapter.

Ron

[vindi93]

Originally Posted by Ed_Dinning

Hi Gents, if anyone is interested I can produce transformers and chokes for these amps.
I think I also have some nice nickle-iron lams for the driver transformers

I am looking for a transformer to run an oc26 off an ef98 valve how ever i don't have much to go on other than 25:1 and 270 ohms

If it was mine I would build the external unit using a modern IC amplifier, loading the EF98 to look like what the transformer was, if it hasn't already got an anode resistor.

[Ed_Dinning]

Winding details for the Mullard transformer are given in the Mullard "reference manual of transistor circuits"

Ed

[vindi93]

this is the schematic as you can see with out the transistor side there is no load on the anode. i have attached the circuit for reference.

[Silicon]

How important is it for you to duplicate the original circuit?

Making a audio amplifier using two unusual transformers could be expensive, bulky and time consuming.

You could amplify the output from the EF98 using a readily available audio amplifier chip or possibly a MOSFET source follower.