Phono Connection for Philco Model 96

Phono Connection for Philco Model 96 - Printable Version

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Phono Connection for Philco Model 96 - TN Allen - 06-25-2016

I have restored Philco Model 96 Lowboy, and understand there was a similar Model 296 that included a phono turntable. I recall seeing a schematic for the 296 with a connection for the phonograph. I've been thinking of modifying the model 96 to use with a Garrard RC 121/4D turntable. I realize I'd need a preamp if I use a newer cartridge. Would anyone have suggestions for the modification?

I should add that I have an AM transmitter and have played 78RPM records as well as CDs through the transmitter and Model 96. I think however that it would be preferable, were it possible, to simplify the setup. In fact, it would be great to play CDs direct to the Philco as well, if feasible.

RE: Phono Connection for Philco Model 96 - morzh - 06-25-2016

http://www.nostalgiaair.org/Resources/182/M0013182.htm

296 sch. Why not just do the same?

RE: Phono Connection for Philco Model 96 - Radioroslyn - 06-25-2016

There's a few ways to go about it. Cheap and dirty is solder a .01 mfd cap to the junction of #28 &30. use the unsoldered end and the chassis for the input. Ground the ant post so you won't hear any radio signals.
You could add a radio /phono switch break the connection from 28 to 30. 28 is the audio output from the radio. 30 is the input to the amplifier. Use a switch to connect either the radio audio (28 ) or the phono to 30.

Terry

RE: Phono Connection for Philco Model 96 - Arran - 06-26-2016

(06-25-2016, 04:34 PM)TN Allen Wrote: I have restored Philco Model 96 Lowboy, and understand there was a similar Model 296 that included a phono turntable. I recall seeing a schematic for the 296 with a connection for the phonograph. I've been thinking of modifying the model 96 to use with a Garrard RC 121/4D turntable. I realize I'd need a preamp if I use a newer cartridge. Would anyone have suggestions for the modification?

I should add that I have an AM transmitter and have played 78RPM records as well as CDs through the transmitter and Model 96. I think however that it would be preferable, were it possible, to simplify the setup. In fact, it would be great to play CDs direct to the Philco as well, if feasible.

I don't think that you would need a preamp at all, the pickup on the model 296 was magnetic so it would have have had a lower output then even a newer ceramic cartridge anyhow. There is an advantage to using the AM transmitter though, you end up using the RF amps in the model 96 as preamps ahead of the audio amplifier stages rather then bypassing those and the detector.
Regards
Arran

RE: Phono Connection for Philco Model 96 - TN Allen - 06-26-2016

(06-25-2016, 07:21 PM)Radioroslyn Wrote: There's a few ways to go about it. Cheap and dirty is solder a .01 mfd cap to the junction of #28 &30. use the unsoldered end and the chassis for the input. Ground the ant post so you won't hear any radio signals.
You could add a radio /phono switch break the connection from 28 to 30. 28 is the audio output from the radio. 30 is the input to the amplifier. Use a switch to connect either the radio audio (28 ) or the phono to 30.

Terry

This works nicely, although I tried grounding the antenna, but that increased the noise. I'll add a switch later.

The volume is adequate with either the Garrard through a cheap preamp, and the CD player connected directly to 28&30. I may want to amplify the input a little more later. It's fine in the small room where the Phico sits presently, but may need a little more volume in a larger room, as it is I have the volume at maximum.

Thank you for the suggestions.

RE: Phono Connection for Philco Model 96 - morzh - 06-26-2016

By grounding the antenna Terry might've meant shorting it to chassis (Gnd post if exists at the same terminal strip with antenna) and not really connecting it to Ground.
Which one did you do?

RE: Phono Connection for Philco Model 96 - TN Allen - 06-26-2016

(06-25-2016, 07:21 PM)Radioroslyn Wrote: There's a few ways to go about it. Cheap and dirty is solder a .01 mfd cap to the junction of #28 &30. use the unsoldered end and the chassis for the input. Ground the ant post so you won't hear any radio signals.
You could add a radio /phono switch break the connection from 28 to 30. 28 is the audio output from the radio. 30 is the input to the amplifier. Use a switch to connect either the radio audio (28 ) or the phono to 30.

Terry

(06-26-2016, 02:45 PM)morzh Wrote: By grounding the antenna Terry might've meant shorting it to chassis (Gnd post if exists at the same terminal strip with antenna) and not really connecting it to Ground.
Which one did you do?

I connected antenna and antenna ground, it has both, as well as a connector designated loc., which connects to one side of the power in across a .015uF capacitor.

There is some static and popping, but perhaps this is to be expected in this radio. Neither are very noticable while playing the Garrard, and vary when playing the radio.

RE: Phono Connection for Philco Model 96 - TN Allen - 06-28-2016

I found the schematic for the model 296 and looking at the phono connection and am trying to understand the phono switch and connection. I understand some of the schematic, but would be grateful for some assistance understanding the way the phono is switched in and out of the circuit, and which of the tubes are the audio amplifier.

The suggestion to connect at 28 & 30 works well, but I'd like to understand the difference between connecting there, and alternately at 24 & 26.

Here is a link to the model 296 schematic: http://www.philcoradio.com/tech/images/296.jpg

Thanks in advance.

RE: Phono Connection for Philco Model 96 - Radioroslyn - 06-28-2016

Hi TN,
The switch on the 296 is doing two things. It's changing the voltage on the 24's suppressor grids to lower the gain of the rf amp stages and switching audio input.
The thing that is a little tricky is that #25 is part of the avc circuit so we want to leave it a lone. The original magnetic cartridge presents a low resistance across the amplifier input. Your modern cartridge doesn't. So what to do? Add a 500k -1M resistor to the control grid of 27 tube to chassis ground. Break the connection at #24 and 26. Add switch with the wiper connected to 26 (that's the audio input) One end of the switch goes to 24 (radio) and the other end to phono cartridge (phono) though a mylar cap a .005-.01 is fine.

Terry