1959 Zenith C845M High Fidelity AM/FM Radio

This radio repair is cross-posted from Rain City Audio

This classic 1959 Zenith C845M radio came into the shop for a full repair after sitting unused for some time. It has the classic late ’50s styling, and a dual speaker high-fidelity design.


It’s an 8-tube radio with a 35C5 output tube good for maybe 3W of maximum output, but it has great sound quality.


Inside, it’s covered in a lot of original dust, and is missing about half of its tubes:


Here’s a good shot of the two speakers, with a single capacitor high-pass filter on the tweeter.


Underneath it’s mostly original although saw some service at one point. Very unfortunately, it’s a series-string radio; otherwise it’s quality construction. There was plenty of room under the chassis to work,  too. Zenith used precision resistors in this build and they were all within tolerance. After the film capacitors, the electrolytic capacitors were replaced.


Component replacement complete:


Time for a first power-up!


And immediately, one of the tubes that had tested earlier immediately blew its filament. So, it was time to replace that tube and for good measure the other two as well, so it received a fully new tube compliment.


Finally, time for an alignment. Using the alignment tool, I adjusted the cores inside the IF transformers. This cleaned up some of the remaining distortion and increased the volume a bit.


The components have drifted a bit so the dial tracking isn’t perfect, but it’s close. Looking carefully, one of the IF transformer has a manufacturing error – the label stamped into the top of the can has an inverted “F” when a technician set the stamp incorrectly.


Back in the cabinet!


I took a video of it tuning through the range on both bands:

This is going to sound great for a long time to come. It does have a phono input on the back where you could connect an external input, but, due to the series string construction it’s not safe to connect anything modern to that input as it’s a shock hazard.


This does justice to the High Fidelity label, it sounds great with the large speaker and dedicated tweeter, and it plays loud and strong on both AM and FM. On AFC, tuning between stations is very crisp. This should be a great daily driver!

Rain City Audio Vintage Radio Repair

More Rain City Audio Projects


Original Article at Rain City Audio

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7 Responses to 1959 Zenith C845M High Fidelity AM/FM Radio

  1. David DeRosier says:

    Nice Job. Would you know what type of dial light would be used with a 5 tube series string radio using 12SA7,12SK7,12SQ7,50L6,35Z5? it is across one side of the Rectifier Filaments.

  2. Richard McLeod says:

    There was no mention about a Dial light. I know that some of these similar models did have a Dial Light and some did not. How about this one? Does it have a Dial Light? Thanks for the clarification. Rich

  3. Jason M. Stafford says:

    I have just recently purchased a similar 1959 Zenith Hi-fi C845E Radio on EBay, however it is in need of some new film resistors and probably electrolytic capacitors as well. WOuld it be possible to purchase a copy of the schematic and or parts lists from you?

  4. Mark says:

    I’ve got the same one playing in my kitchen right now. Love it!

  5. Gary says:

    I have the exact same radio and it plays great. I always loved the tube sound.

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