Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

Thread Closed
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

New to this site and have a Philco 20 question.
#1

Hello Philco radio lovers,

I am new to the group and also new to the TRF radio. I wasn't sure if this Model 20 TRF radio functioned normally. I got this radio recently. The radio worked (it received signals). However, the audio garbbled if the radio received strong signals.

It looked like that there wasn't an AGC circuit in the IF and RF sections. I wonder if this was the reason that caused the distorted audio. Also, I wonder if there are mods (such as adding AVC and diode detector) to improve the receiving performance.


Thank you for your answers.

73,

Jonathan,
AB6LS
#2

Hi Jonathan,
The trf radio has no IF's or avc. Icon_cry It amplifies the rf on the whole band through- out the radio to the detector/first audio amplifier. That is why you get "blaring" on strong signals and have to turn up the volume on weak signals (no avc). Have you recaped the radio yet? A good recapping might be in order. You can find the schematic here. http://www.nostalgiaair.org/PagesByModel...029582.pdf

Hope this helps
Terry
#3

Jonathan - welcome! Another free schematic may be found here.

For the early Model 20 with only one or two trimmers:
http://www.philcoradio.com/tech/images/20a.jpg

For the common Model 20 with three trimmers on the tuning condenser gang:
http://www.philcoradio.com/tech/images/20b.jpg

The 20 could be modified to add AVC, but it would frankly be more trouble than it would be worth - removing coil ends from ground, adding terminals to coil forms, etc. Not to mention detracting from the originality of the circuit.

--
Ron Ramirez
Ferdinand IN
#4

Ron Ramirez Wrote:Jonathan - welcome! Another free schematic may be found here.

For the early Model 20 with only one or two trimmers:
http://www.philcoradio.com/tech/images/20a.jpg

For the common Model 20 with three trimmers on the tuning condenser gang:
http://www.philcoradio.com/tech/images/20b.jpg

The 20 could be modified to add AVC, but it would frankly be more trouble than it would be worth - removing coil ends from ground, adding terminals to coil forms, etc. Not to mention detracting from the originality of the circuit.

Hi Ron and Terry,

Thanks for your feedback. I'd try to see what I can do to make the radio performs a bit better.

I guess the Model 20 probably performs similar to those early 1930 radios or 1920 radio such as Atwater kent Breadboard or Model 20.

Jonathan.




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
PT-6 finished!!
Actually the Loctal tube series, with number beginning with "14" are 12.6 volt tubes, at 150 ma, I'm not sure ...Arran — 02:14 AM
philco predicta
The model is the holiday without UHF It has no sound and I don't have an oscilloscope or signal generator.cgl18 — 08:51 PM
Philco model 38 code 121 not receiving signal.
I will definitely check my lead length and wire dressing. Thanks for the ideas.Stormlord5500 — 08:06 PM
Philco model 38 code 121 not receiving signal.
Do make sure that you twist the 3 wires from the chassis to the transformer, and dress away from tubes, especially audio...MrFixr55 — 07:38 PM
Philco model 38 code 121 not receiving signal.
The cone unfortunately got damaged when I removed it. The glue that held the cone to the basket was sloppily applied and...Stormlord5500 — 07:12 PM
Philco model 38 code 121 not receiving signal.
So what was wrong with the original speaker? Was the cone damaged? Unless it's totally hopeless I would put it aside as ...Arran — 05:31 PM
My collection presentation
There is an article on my site that introduces the first portable radios in my collection. I have only provided a link t...Vlad95 — 01:17 PM
Electrolytic restuffing/internals
Bridkarl This specific cap you have is the easiset type to restuff. I usually cut it at the upper border of the depr...morzh — 11:35 AM
philco predicta
Hi CGL18, First off, welcome to the Philco Phorum. I have not worked on a TV for a while but here are some givens: ...MrFixr55 — 08:22 AM
Another amp build - here I go again!
Sweet! I actually have a Dynaco Mark 4 that I had been running with 6L6s with no mods. Seemed to my 14-year-old head a...MrFixr55 — 12:57 AM

[-]
Who's Online
There are currently 1125 online users. [Complete List]
» 1 Member(s) | 1124 Guest(s)
Avatar

>