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Sparton Model 15 resistor wattage ?

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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » Sparton Model 15 resistor wattage ?
           
Jack Smith
 
 
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21.Jul.20 07:10
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Can anyone tell me the wattage  rating of  the 5 resistors labeled as R2 and R3 on the sparton Model 15 Schematic  ?

Thanks

Jack

Omer Suleimanagich
Omer Suleimanagich
 
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21.Jul.20 07:34
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Any chance that you can associate the model or upload the schematics?

if we can see what you need to know , someone here can help you

Jack Smith
 
 
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21.Jul.20 14:19
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Https://www radiomuseum.org/r/ sparks_wit_15.html

 

On the left side  about 1/2  way down.

 

This article was edited 21.Jul.20 20:20 by Jack Smith .

Omer Suleimanagich
Omer Suleimanagich
 
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29.Jul.20 09:24
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"R2" is two resistors in series, 3.9K ohms and 4.3K ohms

"R3" is three resistors in series, 220 ohms, 60 ohms, 2.1K ohms

I don't have this set in front of me, but I would use 1/2 watt rated resistors  Either carbon film or metal film

It's always a good idea, rather than shotgun replacing parts, try to find out what the curcuit is doing, and why it was designed the way it is for the time when the radio was manufactured  That is what this forum is good for

Don't rely on the original parts either, test EVERYTHING!

C21 should have a safety capacitor in its place

This article was edited 29.Jul.20 09:26 by Omer Suleimanagich .

Jack Smith
 
 
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29.Jul.20 17:54
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Thanks so much for your help!!

Rüdiger Walz
Rüdiger Walz
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30.Jul.20 09:03
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I fear half-Watt resistors are not sufficient. Looking at the schematic I see the field coil and the resistors R2 and R3 in series to the voltage at the cathode of the rectifier valve 80. Assuming worst case a voltage of 420 V at the cathode of the tube 80 and variable R1 at the lower side a current of about 36 mA is flowing through the field coil 1150 + 4300 + 3900 +220 +60 +2100 Ohm resistor. Assuming current consumption of the valves beside the output power valve which is conected before the field coil about 30 mA can be added to the current in the field coil. 

Using the equations R= U/I and P= U x I one can assume a voltage of about 300 V at the electrolytic condenser and the hot side of R2 and R3. This results in a current of about 33 mA  (0,033 A).

Using both equations you get P = R x I,which results infollowing results (rounded):

4300 Ohm / 6 Watts

3900 Ohm / 5 Watts 

220 Ohm / 0,3 Watts

60 Ohm / 0,1 Watts

2100 Ohm / 3 Watts

American scematics aresometimes difficult to read for me and I hope Imade no mistake.

Best regards

Omer Suleimanagich
Omer Suleimanagich
 
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31.Jul.20 10:59
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I actually did not make any calculations, but from restoring a few radios of that vintage, some manufacturers would place one broad "resistor" with feeds.  I don't remember them being large resistors, but they seemed to be power resistors. 

in hindsight , it would be helpful to have pictures of the parts in question

A 6 watt power resistor for a radio of that vintage would be pretty big

Thank you for doing the math, there is nothing worse than putting underrated parts in a radio and see them fail before your eyes!

 

 

 

Rüdiger Walz
Rüdiger Walz
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31.Jul.20 17:10
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Dear Omer,

yes, you are absolutely right. I would also expect a ceramic wire wound resistor with respective feeds. I only wanted to make some rough calculation to beon the save side. 

Best regards

Rolf Beckers
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31.Jul.20 18:05
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Dear Jack,

You have round about 300V and some volts at total resistance of round about 10.000 Ohm makes .03A times 300V makes round about 10Watt.

Regards

Rolf

Mark Hippenstiel
Mark Hippenstiel
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31.Jul.20 18:13
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We have moved this thread to the model page - please start your threads by visiting the page and select "uploads" -> "forum question" so other contributors can find the radio in question quickly.

There's also the Candian Sparton 15 but the schematic there isn't any more helpful.

Thanks
Mark

  
rmXorg