OTL turntable EL86 speaker wiring

[Pauld35]

Hi Paul,

Yes, it's negative feedback, but frequency dependent. It's there to correct the frequency response as recorded on discs and possibly also to correct the frequency response of the pick-up element. The values of the tubular capacitors values are in pf. On Dutch radio forums they are regarded as reliable.

Greetings,
Robert

awsome thanks

 

[Pauld35]

Philips did the same thing in the AG9015.The UPT has several windings, probably for better coupling.
And for those who want more power for 400/800Ω speakers there was the AG9007, 60W in 400Ω !
Mona

wow thanks for posting the AG9007, looked at some of the prices for the philips AG amps .....quite high, maybe will build out of vintage parts though they are pretty nice looking amps though.

 

[Kay Pirinha]

And for those who want more power for 400/800Ω speakers there was the AG9007, 60W in 400Ω !

Hi Mona,
this amplifier is quite another topology, as it is a Circlotron .
Best regards!

 

[Pauld35]

saw an identical one on e-bay in France and used the model number to find a service document. attached it below.



Ancien Tourne Disque PHILIPS AG9128 1958 Haut De gamme RIAA radio gramophone | eBay

 

[OldHector]

The voltage divider sets the control grid to get ± half the supply voltage between the tubes.Since the two are in series the upper one gets the same bias current as the lower, set by it's cathode resistor.
Mona

Hi Ketje,

In the service manual, the B+ is shown as 430, but it is 324 on your diagram. Is that because you have re-worked the operating point for the toroid solution?

EL86 is meant to be similar to PL84, and that tube has a screen voltage limit of 200v. It looks like the top tube has a screen voltage slightly over that (210v). Is the EL86 a bit more rugged than the made-for-TV PL84? I.e. they are only close relatives, and more different than just the heater voltage?

 

[Ketje]

Hi Ketje,

In the service manual, the B+ is shown as 430, but it is 324 on your diagram. Is that because you have re-worked the operating point for the toroid solution?

EL86 is meant to be similar to PL84, and that tube has a screen voltage limit of 200v. It looks like the top tube has a screen voltage slightly over that (210v). Is the EL86 a bit more rugged than the made-for-TV PL84? I.e. they are only close relatives, and more different than just the heater voltage?

The 324V is my idea, it comes from EL504, #36.
430V is fine, you have to substract the voltage over the cathode resistor.
The datasheet from EL86 and PL84 are the same, 5% more or less is nothing to worry about for tubes.
Mona

 

[Kay Pirinha]

Besides the heaters, EL86 and PL84 are exactly the same tubes. As is any other member of the .CW5 family, but also the 45B5/UL84, which at least in Europe was the ancestor of all these tubes.
Best regards!