Philips All transistors and ground-negative circuit

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Philips All transistors and ground-negative circuit

Berichtdoor oldphilips » vr aug 28, 2009 8:35 am

Hi,

I'm not sure I'm posting in the right section, but here it goes...

A huge majority of the All Transistor circuits made in the 60s were ground-positive : turntables, radios, reel-to-reel recorders, etc... That was the case with the units made by Philips too of course.

Does anyone know of a unit (turntable, radio, tape recorder...), Philips or not Philips, from this era (the 60s) that would be ground-negative ?

Thanks !
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Re: Philips All transistors and ground-negative circuit

Berichtdoor Thomas » vr aug 28, 2009 12:43 pm

As far as I know, all Philips devices were ground-negative. Since multiple voltageswere often used, I can't think of any situation where groud-positive was even a handy solution.
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Re: Philips All transistors and ground-negative circuit

Berichtdoor Henk D » vr aug 28, 2009 8:54 pm

Germanium transistors have been used for the ''all transistor'' equipment of the early sixties. And since germanium transistors are in almost all cases of the PNP type (AC127 is one of the exceptions to this rule) and the devices are operated in a common emitter connection, a ground positive scheme is the obvious choice.
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Re: Philips All transistors and ground-negative circuit

Berichtdoor oldphilips » vr aug 28, 2009 9:31 pm

And since germanium transistors are in almost all cases of the PNP type (AC127 is one of the exceptions to this rule) and the devices are operated in a common emitter connection, a ground positive scheme is the obvious choice.

Yes, quite right.
But at the same time it is possible to make some ground-negative circuits with some PNP transistors (even if it's technically harder, so not the obvious choice).
It could have been necessary, because it was connected to something that was already ground negative : car radio comes to my mind. Again, was it the case ? Were Philips car radios sometimes ground negative ? Or was it the case with some other devices (recorders...) ?
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Re: Philips All transistors and ground-negative circuit

Berichtdoor Henk D » za aug 29, 2009 8:02 am

For car radios it was indeed required to have a ground negative connection. The Philips 22RN464 for instance (MW/LW carradio, equipped with germanium transistors) does have a selector for -6, -12 and +12V supply voltage.
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Re: Philips All transistors and ground-negative circuit

Berichtdoor oldphilips » za aug 29, 2009 10:21 am

Hi Henk,

thanks for your answer. I have found some service manuals on radiodatabase.nl, but not for your 22RN464. Do you know where I could find some more ?

Thanks a lot.
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Re: Philips All transistors and ground-negative circuit

Berichtdoor Thomas » za aug 29, 2009 11:05 am

For Philips Service Manuals, see http://www.nostatech.nl . Mr Manshande has a huge collection of manuals, which may feature that specific radio.
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