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1927 Eveready (National Carbon) Model 1 TRF Radio
#31

Thanks Mike! It only took me about 2 weeks to get it going.  Icon_thumbup  Icon_e_biggrin
#32

Hi Cap'n Clock,

Other than the push pull output (nice to have), this circuit is very common to the era, similar to Atwater Kent 40 and RCA Radiola 18.  Might be a Neutrodyne.  For filaments and heaters, the '26s run on 1.5V, the 27 on 2.5v and the 71s on 5.0V.  the 80 is on its own 5V secondary because the filament is the cathode and is 200V or more above ground.   

The filter capacitors in the power supply are likely oil filled and not electrolytic.  Be careful disposing of them as they may be toxic.

You can start out with the existing speaker until you get further in the restoration,  This does not look a dynamic speaker, it is magnetic, similar to a Radiola 100A Speaker.  It can be patched either with coffee filter if the original paper has not ripped off and gotten lost.  You can use black construction paper if you want something thicker.  High impedance, maybe 1K Ohm.  the secondary of that push pull output transformer is alikely also about 1KOhm. Some folks think they should be good, others say replace them  In this case, since the Rider's schematic for this radio has instructions for replacing the "Filter Pack", definitely replace the filter caps. You can use a speaker and output transformer from an AA5 (5 Tube radio) from the 1950s for testing purposes.  Plug the red and blue primary wires into the pin jacks.  If you are looking to keep  the radio original looking, reproduction cloth covered wire is available, but not cheap.  Phoneco, Inc (google it) has a speaker cord with pin plugs on one end and spades on the other for $9.75  Lamp cord is an anachronism but will work just fine and will be safe.

Many techniques are used to deal with the rubber wire from absolute replacement to disconnecting one end, slipping heat shrink tubing or "Spaghetti" over the wire and resoldering the disconnected end.  Remington Wire sells a nice kit with about 25 feet per color, 6 different colors for $30.00.  UL Listed, 300VDC Insulation.  Available on ePay.  not what was used to build the radio but will  work just fine.  Should be good enough for this job.  Cloth covered wire is available from many sources.

2 safety steps:
Install a fuse in the power line, on the high (switch) side.  1Amp fast will do, I think, if the specification is less than 100 Watts.
Install a 1N4007 in series between each Power Transformer HV secondary lead and each plate of the rectifier tube with the cathode of each diode facing the plate of the rectifier tube.  This will protect the transformer if the rectifier tube shorts.  Lost a Philco console as a kid when the rectifier shorted (I cant remember the model but it uncharacteristically had a 5Y3 instead of  car radio type 84 rectifier that Philco commonly used.  House filled up with smoke, Mom completely freaked and made me throw it out.  No explaining it to her!  Heck, I was playing with a washing machine motor when the Great Blackout of 1965 occurred.  Dad came home (His car had the working radio), and tells Mom that the lights are out as far west s Chicago. Mom then informed him that I caused the blackout.

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards, 

MrFixr55
#33

It's unlikely that a set this old would have used oil caps, more then likely they were large paper caps, stuffed in the bottom of the filter block. Since this set was based on an American Bosch model 28, which was a reworked Radiola 17 or 18, this was haw it would have been constructed, and they are actually fairly easily removed in those two sets, the hardest part is unbending the metal tabs that hold the can in place. These set were straight TRF, no Neutrodyne, Neutrodynes use an extra winding on each RF coil for inverse feedback, the Radiola 17 and 18 used neutralizing condensers.
Regards
Arran




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