CANDOHM resistor zenith: (5-S-218AT Ch=5521AT); 5S218AT
This model radio employs a three section "candohm" resistor (R10) working as a voltage divider to obtain the negative bias voltages for the 6Q7G and 6F6G tube grids.
The schematics does not gives the ohm values for this "candohm".
I've search over to get these.. but has no success.
I wonder if maybe someone could give a clue with this matter.
attached is a schematics with all the voltages.
- Zenith Chassis 5521 (123 KB)
On a schematic of a 6-S-52 Zenith I found a six-section Candohm. Three of the six sections performed the same functions as the three-section Candohm in your 5-S-218AT. Those values are actually given on that schematic and the three sections in question would be:
first section, from center tap of HV winding/- side of 8µF 450V to 220k/1M/g1 of 6Q7: 250 ohms
second section, from 220k to k/g3 of 6F6G: 74 ohms
third section, k/g3 of 6F6G to earth/ground: 83 ohms.
I don't know if you have tried measuring any of the actual resistances of your original Candohm to see if any of these values match or are at least close, but these could be a starting point...these would probably need to be multi-watt resistors; and these exact values are not readily available; you would need to substitute probably 240 or 270 ohms for the 250, 75 ohms for the 74, and 82 ohms for the 83,,,
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