The PHILCO Phorum
New to Phorum - picked up Zenith S652 and RCA811K - Printable Version

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RE: New to Phorum - picked up Zenith S652 and RCA811K - MrFixr55 - 02-22-2021

Hi Folks,

I agree that the 6S52 (and table model 6s27 which uses the same chassis) is a major performer given the circuit. It is a 6 tube, sure, but no RF Amp. he tube coubt is 6 the 2nd detector is separate from the first audio amp Usually, they are combined in a 6Q7 or similar tube.

Had a chance to buy one of these for 1.00 when i was a kid in 1967. Dad wouldn't let me. Kid down the road ought it because he wanted to make a guitar amp out of the speaker and cabinet. He gave me the chassis and I have it to this day. I don't know if he was successful, as he did not know enough about electronics to power the field. Now that I am eBay literate, I am looking for a 6S27 (table model) cabinet only, to put the chassis in. Amazingly, it has all the original caps except the filters that I replaced years ago. I should recap it, but amazingly, there is no drippage from these caps. However, definitely recap yours. As you can see, there is plenty of room to work inside the chassis. This radio dates to 1936. Fix the chassis and enjoy it as you refinish the cabinet.

Everyone is right. The Black Dial is cool when lit. The Lightning bolt Z freaks my wife out!


Best Regards,

John, "MrFixr55"

RE: New to Phorum - picked up Zenith S652 - Steve A - 02-24-2021

Thanks, Mike. Regarding the Candohm, what are the resistors and values I need if I build a replacement on a terminal strip? What else would be needed to replace the Candohm? Also, in the schematic the resistors R5 and R7 respectively, are stated simply "Tone Control" and "Volume Control"- no ohms or wattage listed. Can anyone tell me what the resistors are for these two?

RE: New to Phorum - picked up Zenith S652 and RCA811K - MrFixr55 - 03-17-2021

Hi Steve, 

If no one has posted answers to your last questions:

The volume and tone controls are usually 1/2 watt.  The volume control likely should be 500K Ohm, or 1 Meg Ohm, and importantly, "Audio Taper".  A 100K  Ohm should work for the Tone Control if yours is bad.  You can measure between the 2 end connections to get an idea of the actual resistance. Try cleaning them before replacing them.  Caig DeoxIT ™ is popular among a lot of experts.

The Candohm Resistor is represented by the "string" at the top right of the Rider's Schematic for the radio.  It is a rather clever voltage divider for both "B" and "C" (bias) voltages.  It is important to get the resistances in the correct Order.  From B+ to center tap of the transformer (C-, based on the fact that the center tap is more negative than chassis ground, common in radios of this vintage) is:
11 KOhm, 4940 Ohm, 920 Ohm, 83 Ohm, 74 Ohm, 250 Ohm.  5 Watt wire wound ceramics would be fine, and may be overkill for some of these.  a 5 Watt for the 11K Resistor and 3 Watt metal film for the rest of them should be OK.  You will likely not get exact values for these resistors.  If the error is 5% or less, there will be no issue.  For example, substituting a 5 KOhm resistor for the 4940 Ohm resistor is an error of about 1.2% 

Note that the diagram calls the resistance closest to the junction of the field coil and B+ to the Audio Output stage is listed as 11M.  This is confusing but M in this context on schematics of this vintage is the same as Kiloohm, KOhm or Ohm x 1000.  For resistances in the Megaohm range, Megaohm or Meg is the usual marking on schematic of this vintage.

I welcome the comments of the experts as to my recommendations.  Any difference of opinion, please take the recommendations of the experts and moderators over mine.

There is one other recommendation that I have.  I do not remember where I saw this but considering adding a 1N1007 Rectifier between each leg of the Power transformer and the Plate of the 5Y3 Rectifier with the cathode (band end) connected to the plate and the other end to the transformer.  This will protect the transformer if the rectifier tube shorts.  Filament heater type tubes like the 5Y3, 80, etc. can short filament to plate if the filament opens.  This happened to me as a kid on a nice Philco console (Can't remember the model, but must have been early post war because the older ones had a Heater style cathode in the rectifier tube, such as 84 and 7Y4 types).  Filled the house with smoke and stink from a burning power xformer and Mom freaked.  She made me put it right out to the curb,  Dad knew what happened but wisely demured to Mom.  He knew that discretion was the better art of valor.

Good luck on your restoration!

John "MrFixr55