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R-90 radio transformer
#7

Hi Frowland,

Welcome to the Philco Phorum and the radio collection, repair and restoration hobby!

As others have stated, especially Bob (Klondike98), this is a reproduction, made in the 1980s, using a modern solid state AM-FM radio circuit. This is good and bad news. The good news is that a modern, solid state is usually more reliable than 85 -100 year old tube circuits, and the availability of FM means a higher fidelity method than AM for music.

The bad news is that this Asian reproduction is not as valuable as a restored and working Model 90 (one of the iconic Philco designs and cabinets of this era). In addition, documentation and parts are likely not available for this reproduction.

Where does it state that the AC Power Input Frequency is 80Hz? Almost all power throughout the world is currently either 60Hz (USA, Canada and most of the rest of the Americas, most of Japan and many other Pacific Rim countries) or 50 Hz (most of Europe, some of Asia, some of South America) A transformer designed for a higher frequency will not work and possibly burn out on a lower frequency, but a transformer meant for a lower frequency should work at a (reasonably slight) higher frequency.

Is the transformer missing or burned out? Does it smell of being overheated. Have you "ohmed" the primary and secondary?

How many wires toes the transformer have? If only 4 wires, then it has only one secondary.

I would hazard a guess that this transformer has a single secondary and that the power supply of this chassis consists of a bridge rectifier and a rather large capacity filter capacitor. This is rather common for AC powered solid state radios of relatively low output power. Look for a bridge rectifier or 4 individual rectifier diodes (1N4001 or similar) on the PC Board. The largest capacitor on the board is likely near this rectifier and is likely the filter capacitor. (Make sure to not confuse the power supply filter capacitor with the output capacitor that may be used to couple the power amplifier to the speaker.) Note the voltage rating on the capacitor. If 16V, then the power supply output ls likely between 9 and 12 V. Ohm across the capacitor. You will get a low resistance reading that will increase eventually to infinity. With the transformer out of the circuit, ohm where the secondary was soldered to the board. Verify no shorted diodes. If any diodes are shorted, they need to be replaced. if individual diodes were used, 1N4007s should do. If a packaged bridge was used, look up the number on the internet. A 4 A (Amp) 400PIV (Peak Inverse Volt) unit would more than suffice, but it is likely that the rectifier is a 1A 50PIV or 1A 100PIV unit.

Once you have confirmed that the power supply is not shorted, you could "tack solder" 2 wires to the capacitor (red to positive and black to negative) and attempt to power the radio. If the filter capacitor is rated at 16 VDC, start with 9V and increase to 12V using batteries. do not accidently reverse polarity! This will toast the radio! If the radio plays, you are on the right track.

Hope this helps. Good Luck!! Keep us posted and add pictures of the transformer as well as the top and bottom of the chassis.

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

MrFixr55


Messages In This Thread
R-90 radio transformer - by frowland - 02-07-2024, 10:10 AM
RE: R-90 radio transformer - by klondike98 - 02-07-2024, 01:26 PM
RE: R-90 radio transformer - by Arran - 02-07-2024, 01:45 PM
RE: R-90 radio transformer - by klondike98 - 02-07-2024, 02:28 PM
RE: R-90 radio transformer - by Radioroslyn - 02-07-2024, 04:18 PM
RE: R-90 radio transformer - by Arran - 02-07-2024, 06:24 PM
RE: R-90 radio transformer - by MrFixr55 - 02-07-2024, 11:32 PM



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