Part # 1445, voltage divider network

[Randy Rago]

Or if in the Zenith world, a "Candohm". In the masterpiece, its 3825; 980; 780; 1975 ohms. Im replacing it with discreet power resistors. 5 or 10 watters?

[George]

Yes those Candohm resistors always seem to fail despite their apparent rugged appearance in many other radios. For durability it’s always wise to choose replacement resistors with an increased wattage rating.

[Randy Rago]

I know, but thers no rating on the schematic. Or is a parts list published? Thx

[Randy Rago]

Nevermind, did the math. 6 watts, using 10 watters

[Kent King]

They wattage can be calculated via Ohm's law and the power formula. However, to shortcut those calculations, if you make each a 5W unit, you should be ok. Making the big one (3825) a 10W unit would be prudent. I never noticed the schematic shows two different resistors with the same voltage drop. If they are, in fact 980 and 780, the drops won't be exactly the same, 980 should be closer to a 30V drop and 780 nearer 20V...in practice, with our higher line voltages, everything will probably be higher, and as long as they are consistent with each other, the set will operate just fine.

Kent

[Randy Rago]

230v drop across 7560 ohms gets me close to 6 watts across the array. So 10 watters will be good. Nice catch on that noted 25v drop across two different values!

Factor in a +/- 20 % tolerance and im fine. Thanks for the input.

[Randy Rago]

After some time off, I’m back into the Masterpiece project. Thanks to all who helped before with the grid wiring. Im at a major roadblock with the bias resistor network. Previously, the first value after the 230V showed 6100 ohms way out, the rest of the string measured good. I installed a 2k 10 Watt in place of the first resistor. I’ve got the 230VDC going in but then I’ve got  81v, 50v, 35v down stream.. Should be 230, 150, 125, 100.

the audio section is working well, through the phono input, but over the air is dead.

Is there a schem. with socket voltages or is that the holy grail? I checked the Super VII schem, but it also does not have socket voltages. Am I missing something obvious??

All I  have is a clue – when I turn off, I get a brief moment of reception. Is this an indication of  B+ /B- imbalance?

 

Thanks in advance Happy New Year

[David C. Poland]

so, something sucking off voltage after the first 2K section of the B+ voltage divider? Have you replaced all the various original paper/wax/foil caps in the receiver? If so, then You might try detaching each wire off the B+ divider (one at a time) and see if when one of them when detached suddenly restores the other voltages, then trace out that suspect circuit. 

[Randy Rago]

Thanks, David.
Im not a shotgun repairer, i change then test so i dont loose my place. Lack of detailed documentation has not helped. I have read that Scott published troubleshooting docs but seems they're rare.
So before i disconnect and light up B+ glad i checked here first.