Philips radiogram F8X82A (Techniek Radio/TV)
door Pandu Rajan 
, 11.02.2020, 17:52 (1752 dagen geleden)
Dear friends
In this set two transformers have been used - S112/S113 and S114/S115 in the O/P circuit. What is the use of these transformers?
Regards
P.Rajan
Philips radiogram F8X82A
door Maurice 
, Dordrecht, 11.02.2020, 18:49 (1752 dagen geleden) @ Pandu Rajan
Isn't it kind of Ultra Linear principle?
Normaly the amp has then a centertap on the output pransformer and connected to the 2 grid.
"In 1951 , David Hafler and Herbert Keroes introduced a pentode power amplifier, inwhich a tap of the
primary transformerwindingwas connected to the screen grid of the power pentode . They called
this the Ultra-Linear power amplifier. This power amplifier shows the advantages of a triode, low
anode AC internal resistance and low distortion, as well as the advantages of a pentode, large delivered
anode AC power and good efficiency. The narrative given by David Hafler and Herbert Keroes
is good and substantiated in practice; this is very important."
--
"I haven't even turned this on to see if it works because as long as I don't it might"
Philips radiogram F8X82A
door Maurice , Dordrecht, 11.02.2020, 18:54 (1752 dagen geleden) @ Maurice
Bewerkt door Maurice, 11.02.2020, 19:28
Ofcource
About the F8X82A lezing-bernard-terlingen-philips-f8x82a-deel1
https://www.youtube.com/watch?v=9bVXLZ9zRi4
It is a dual driven Tube that Top tube EL86.
As wel as through normal G1 as now G2 through that left capacitor and transformer.
Also the transformer powers the ECC83,as wel as full output signal on that ECC83 in supperposition.
So positive coupling.
The botum tube has though the most lower resistor line Liniear feedback,and
upper ECC83 throug the 33k on that feedback and so that way also positive feedback.
So bottum ECC83 has negative feedback as the uppertube ECC83 positive feedback.
Resulte a big negative feedback is compensated through 2 times a positive feedback at the top ECC83.
That way a hudge dynamic expancion.
The lower current feedback is frequency independed , low as high is in the feedback.
The lower part of the amp is somewhat a normal amplifer configuration with transformerless output.
Beware!
Those 2 parallel capacitors.
IF afther long time you power Up this amp and you did not reforme and check those
capacitors, it is finito 9710.
Philips data both max 2mA zo 4mA total.
The transformer has very thin wire.
A continuos current through that transformer in rest case.
And so through that 800 Ohm speaker with very thin wire.
So becarfull and double check those capasitors.
The leak current does not excess that max current.
--
"I haven't even turned this on to see if it works because as long as I don't it might"