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 Post subject: Common resistor values and wattage for tube radios
PostPosted: Jun Tue 18, 2019 4:32 am 
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Joined: Jan Sun 20, 2019 7:42 am
Posts: 71
Hi All,

Does anyone have information on resistance values of commonly resistors used in old tube AM/SW radios for example 10 K ohm and 1M ohm etc..?

A local supplier offers me resistors sold in bulk at very good pricing and I am not able to buy all values.

What are common wastage of these common resistors should I buy? Is that 1/2 W (or 1/4 W)?

Thanks

O.C


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 Post subject: Re: Common resistor values and wattage for tube radios
PostPosted: Jun Tue 18, 2019 7:10 am 
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Joined: Sep Thu 23, 2010 6:37 am
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Location: Powell River BC Canada
1, 2.2, 3.3 4.7, 5.6, 6.8 8.2 1/2 watt mostly 1 watt sometimes.

These are the 20 % i.e. color , color, (number, number, color number of zeros.

47 ohm yellow , violet, black

560 ohm, green , blue brown

6800 blue, slate, red.

Everyone dies with too many resistors. :shock:

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 Post subject: Re: Common resistor values and wattage for tube radios
PostPosted: Jun Tue 18, 2019 8:21 am 
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radiotechnician wrote:

Everyone dies with too many resistors. :shock:

No one dies with enough .047 uF capacitors... :wink:

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 Post subject: Re: Common resistor values and wattage for tube radios
PostPosted: Jun Tue 18, 2019 12:31 pm 
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Location: Minneapolis, MN USA
Common wattage for tube radios is 1/2 and 1 watt and to a lesser extent 1/4 watt. A few select circuit locations will sometimes use 2 watt. A wise approach is to stock a single wattage such as 1 or 2 subbing them for lower watt values and buying higher watt values as infrequently needed. No need to stock several watt values unless you like to use up many dozens of parts drawers.


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 Post subject: Re: Common resistor values and wattage for tube radios
PostPosted: Jun Tue 18, 2019 12:59 pm 
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Location: Montvale NJ, 07645
I use only 1 watt to replace the common 1/2 watt in tube radios. They match the size of the old 1/2 watt resistors better, plus they have a higher voltage rating than new 1/2 watt units. As for values, look at JustRadios (ad on the right) resistor kits and they will give you a good idea of what values to stock.


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 Post subject: Re: Common resistor values and wattage for tube radios
PostPosted: Jun Tue 18, 2019 10:38 pm 
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Location: Ohio 45177
I would guess that some well used values are like, 2.2M, 1M, 470k, 220k, 100k, 56k, 47k, 33k 22k. for half watt units. Most of the time the higher values handle very little power, being tube bias resistors. When you get down to 10k and below, you start needing one or two watt values. Values of 1k or below are used for stuff like cathode bias, power supplies, etc. and need higher wattage ratings. You would probably find 1k 680 560 470 330 and 220, 150, 100 in one or two watt ranges for those purposes. I would lean toward two watt. Actually you will possibly find any of the 10 or 20% type resistors between about 2 meg and 100 ohms in an old tube radio. Alot more than the half dozen or less values you will need for replacing paper caps with plastic types. Unless you want to make a substantial expenditure ahead of time, you will just have to do like alot of us and either settle for using resistors in parallel or series once in awhile, or just waiting for an order in the mail for those last two resistors to finish the job. If you stuck to AA5 type radios, the variety of electrolytic filter caps would be pretty small too. AC DC AA5 radios all use about the same voltage ratings. Transformer sets need values from maybe 250 up to at least 450 volts types.

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 Post subject: Re: Common resistor values and wattage for tube radios
PostPosted: Jun Thu 20, 2019 6:10 am 
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Joined: Jan Sun 20, 2019 7:42 am
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Thanks All.

O.C


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 Post subject: Re: Common resistor values and wattage for tube radios
PostPosted: Jun Thu 27, 2019 4:58 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Freeport, LI, New York 11520
wazz writes.....
"Transformer sets need values from maybe 250 up to at least 450 volts types."

E-Caps you'd have to be careful with. Just about any e-cap in a power supply, with the exception of a cathode e-cap, I usually use 450 VDC and sometimes up to the 600 VDC jobs. It all boils down to being observant of what was in there in the first place. I've made the mistake of putting the wrong voltaged e-cap in a PS circuit and once the smoke cleared, realized the mistake too late. The funny thing is that I will run up the circuit with a variac and a milliammeter but the degradation process could take up to a minute or two.....all the while you're thinking everything is fine and looking at something else.

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 Post subject: Re: Common resistor values and wattage for tube radios
PostPosted: Jun Thu 27, 2019 7:12 pm 
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Jim Koehler wrote:
wazz writes.....
"Transformer sets need values from maybe 250 up to at least 450 volts types."

E-Caps you'd have to be careful with. Just about any e-cap in a power supply, with the exception of a cathode e-cap, I usually use 450 VDC and sometimes up to the 600 VDC jobs. It all boils down to being observant of what was in there in the first place.

In transformerless AA5/6's, I'll simply replace any 150 volt Electrolytic with a 160 volt unit. Haven't had any problems in doing it this way over the last 20 years or so.

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