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All, Starting to work on this radio. Have schematic But its Terrible quality
But the Caps are labeled 16UF and 8UF But NO voltage listed Also on actual caps NO markings One is 2 IN in DIA other is standard 1 3/8 in
What voltage rating?? Also there is a Resistor across the + leads that's NOT on schematic Its a 400 Ohm 2 Watt Dogbone Resistor Looks original??
Anyone work on this Model Number?
Skip
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Hello Skip,
Looking at the Schematic diagram for that I would use Filter capacitors of no less then 450 volts the higher the better here is the schematic diagram .
Sincerely RichardÂ
http://www.nostalgiaair.org/PagesByModel...028817.pdf
(This post was last modified: 09-23-2022, 12:12 AM by
radiorich.)
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Actually, looking at the schematics, 450 V filter condensers should be fine. The highest voltages they should see seems to be 280 V, and according to the voltage tables the plate voltage on type 80 rectifier is 350 V, so 450 should be fine.
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Hi Skip,
Sounds like someone wired the power supply wrong. The positive side of the caps should be connected together and the negatives have the speaker field coil between them to provide a voltage drop for the output tube grid bias as well as the speaker field. Maybe the speaker has been replaced with a PM?
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Hi Skip,
Good to see last weekend (Ktown). I'll mention a couple of things that are a little different about this set than the average bear.
The p/s uses negative lead filtering. This means the positive sides of filter cap are connected together. The negative side connects the ct of the pt and then to the field coil. The other end of the field coil connects to ground as does negative of the 2nd filter cap. The field coil provides - voltage drop that creates the bias voltages for the 47.
The 47 tube has a rheostat in parallel it's filament. This is adjusted for minimum 60cy hum after the set is back together. No avc and vol control is a rf gain control, has nothing to if the audio circuits.
GL with your new project!
ps Rod is a faster typist than I.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 09-23-2022, 08:18 AM by
Radioroslyn.)
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Thanks all, I will check wiring to see whats going on.
Will let everyone know.
Thanks
Skip
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Terry, I had a little help from my tablet. But you responded more eloquently.
I think it's interesting the different ways these '30s engineers came up with the negative bias voltages, this one seems to waste the least power.
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Ok checked wiring found this..
Across the field coil there is 2 resistors tied in series and ctr taped one is a 1Meg other is a 200K mine has a 500K in place of the 1 MEG...
Other is mine has a 400 ohm 2 watt resistor between the 16uf and the 8uf caps schematic says it should not be there .. the both positives should be connected together
my speaker does have the field coil and output trans both measure good.
Skip
