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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Sat 17, 2018 12:36 am 
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john8750 wrote:
john8750 wrote:
I forgot to try a different resistor. I have a 470ohm 10watt sand type. An easy thing to do, and would much rather have the circuit working as designed. That resistor should not be so hot.



Yes- I changed the resistor and put the 2.2uf cap back in. 13.3volts, and a cool resistor. just slightly warm. I guess the sand type is the best suited for a ballast resistor.
Glad it works now.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Sat 17, 2018 2:12 am 
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john8750 wrote:

It was a 5watt, epoxy carbon? Look at picture.
Now it is a 10watt sand.
Works good now.

Attachment:
rprop.jpg

John:
Sorry buddy but you've got somthing else funny going on there.

Running 1.4 watts through a 5 watt resister should be only slightly warm... NEVER hot.

In fact as a test... I just put two 1 watt 220 ohm resistors in series.
That's a 440 ohm 2 watt resistor ... right?

I put 25v DC across the 440 ohms and it was drawing 57ma. ( .057A x 25v = 1.4 watts)
That's almost exactly what you're doing.... right?

These two 1watt resistors in series are running so cool i can easily hold them in my fingers ... no prob.

So you should CHECK the 470 ohm resistor value you removed. Maybe it's only 47 ohms.

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Last edited by Pbpix on Mar Sat 17, 2018 9:38 am, edited 1 time in total.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Sat 17, 2018 5:16 am 
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Pbpix wrote:
john8750 wrote:

It was a 5watt, epoxy carbon? Look at picture.
Now it is a 10watt sand.
Works good now.

Attachment:
rprop.jpg

John:
Sorry buddy but you've got somthing else funny going on there.

Running 1.4 watts through a 5 watt resister should be only slightly warm... NEVER hot.

In fact as a test... I just put two 1 watt 220 ohm resistors in series.
That's a 440 ohm 2 watt resistor ... right?

I put 25v DC across the 440 ohms and it was drawing 57ma. ( .057A x 25v = 1.4 watts)
That's almost exactly what you're doing.... right?

These two 1watt resistors in series are running so cool i can easily hold them in my fingers ... no prob.

So you should CHECK the 470k resistor value you removed. Maybe it's only 47 ohms.



Now that is something I should have done, but did not. I will check it out. The resistor I have there now also runs cool.
Thanks for that Peter.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Sat 17, 2018 9:23 am 
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john8750 wrote:
The resistor I have there now also runs cool.
Thanks for that Peter.

Yes... but that one is TEN watts .... right?

I am only using a 4 watt resistor and its not hot.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Sun 18, 2018 5:00 am 
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Pbpix wrote:
john8750 wrote:
The resistor I have there now also runs cool.
Thanks for that Peter.

Yes... but that one is TEN watts .... right?

I am only using a 4 watt resistor and its not hot.



My resistor is 467ohms, so go figure. Maybe it is a fake.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Sun 18, 2018 5:08 am 
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john8750 wrote:
Pbpix wrote:
john8750 wrote:
The resistor I have there now also runs cool.
Thanks for that Peter.

Yes... but that one is TEN watts .... right?

I am only using a 4 watt resistor and its not hot.



My resistor is 467ohms, so go figure. Maybe it is a fake.


Close enough to 470 but still curious that it would get so hot.

Try putting it on an AC or DC power supply if you have one and put 25 volts across it (54ma) and it should NOT get hot.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Sun 18, 2018 7:10 am 
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Yes, I will try that with a few different types. Got me curious too. Will do it tomorrow.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Mon 19, 2018 12:15 am 
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Peter- I put two 220ohm 1watt resistors in series. My test voltage is 28.61volts. Current draw is 65ma/1.85watts. There is no way I could even touch the resistors, certainly not hold them.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Mon 19, 2018 12:32 am 
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john8750 wrote:
Peter- I put two 220ohm 1watt resistors in series. My test voltage is 28.61volts. Current draw is 65ma/1.85watts. There is no way I could even touch the resistors, certainly not hold them.

At 1.8watts you're right near the 2watt limit.

Try doing it a. 1.4 watt. (25v)
I could easily hold two220 ohm 1 watt resistors in series that way.

If your stuck using 28v try a 560 ohm 2 watt
or two 270ohms 1 watters in series = 540 ohms =51ma

28v x .051 = 1.45w

Be sure of the wattage rating of the resistors you're using.
If you're working with 1/2 watters you'll sizzle a bit.. yes.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Mon 19, 2018 5:49 am 
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Pbpix wrote:
john8750 wrote:
Peter- I put two 220ohm 1watt resistors in series. My test voltage is 28.61volts. Current draw is 65ma/1.85watts. There is no way I could even touch the resistors, certainly not hold them.

At 1.8watts you're right near the 2watt limit.

Try doing it a. 1.4 watt. (25v)
I could easily hold two220 ohm 1 watt resistors in series that way.

If your stuck using 28v try a 560 ohm 2 watt
or two 270ohms 1 watters in series = 540 ohms =51ma

28v x .051 = 1.45w

Be sure of the wattage rating of the resistors you're using.
If you're working with 1/2 watters you'll sizzle a bit.. yes.



I think we will always get the same measurements Peter.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Mon 19, 2018 9:20 am 
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john8750 wrote:
Pbpix wrote:

Be sure of the wattage rating of the resistors you're using.
If you're working with 1/2 watters you'll sizzle a bit.. yes.



I think we will always get the same measurements Peter.

Yes... the measurements will fit the math.

But if your test was driving 59ma then it's 1.8 watts which is hotter than 54ma producing only 1.4 watts.
There's no magic here. So ...why is it that I can easily hold the resistor in my hand and you cannot because it's too hot??

If you think you have a 1 watt resistor but maybe it's 1/2 watt instead ... that'll smoke your skin too.

I triple checked it here today on my bench AGAIN ...with two 220 ohm 1 watters in series =440ohms, with 25v DC ... across the 440ohm total. 25/440= 56ma.
And 56ma x 25v = 1.4watts

It was NOT hot.. just warm and I can hold it.

Why?

No magic.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Mon 19, 2018 5:23 pm 
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Pbpix wrote:
john8750 wrote:
Pbpix wrote:

Be sure of the wattage rating of the resistors you're using.
If you're working with 1/2 watters you'll sizzle a bit.. yes.



I think we will always get the same measurements Peter.

Yes... the measurements will fit the math.

But if your test was driving 59ma then it's 1.8 watts which is hotter than 54ma producing only 1.4 watts.
There's no magic here. So ...why is it that I can easily hold the resistor in my hand and you cannot because it's too hot??

If you think you have a 1 watt resistor but maybe it's 1/2 watt instead ... that'll smoke your skin too.

I triple checked it here today on my bench AGAIN ...with two 220 ohm 1 watters in series =440ohms, with 25v DC ... across the 440ohm total. 25/440= 56ma.
And 56ma x 25v = 1.4watts

It was NOT hot.. just warm and I can hold it.

Why?

No magic.


I don't know.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Mon 19, 2018 11:20 pm 
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john8750 wrote:
Pbpix wrote:
john8750 wrote:
Yes... the measurements will fit the math.

But if your test was driving 59ma then it's 1.8 watts which is hotter than 54ma producing only 1.4 watts.
There's no magic here. So ...why is it that I can easily hold the resistor in my hand and you cannot because it's too hot??

If you think you have a 1 watt resistor but maybe it's 1/2 watt instead ... that'll smoke your skin too.

I triple checked it here today on my bench AGAIN ...with two 220 ohm 1 watters in series =440ohms, with 25v DC ... across the 440ohm total. 25/440= 56ma.
And 56ma x 25v = 1.4watts

It was NOT hot.. just warm and I can hold it.

Why?

No magic.


I don't know.

That's why I asked you to set it up with exactly 54ma (1.4watts)
AND to double check that you have two 1 watt resistors in series not two 1/2 watt.

So ?

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Tue 20, 2018 2:32 am 
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I will get to it tomorrow Peter. Sorry, very busy today....

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Tue 20, 2018 9:20 pm 
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I did some more testing and the resistors are still too hot to touch.
I used two 220ohm 1watt resistors. The actual resistance is 441.6.
Test voltage is 21.68. 41ma. Or 1.06watts.
Are you sure your resistors are 1watt?
Attachment:
20180320_125724.jpg
20180320_125724.jpg [ 102.21 KiB | Viewed 1305 times ]

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Tue 20, 2018 10:00 pm 
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john8750 wrote:
I did some more testing and the resistors are still too hot to touch.
I used two 220ohm 1watt resistors. The actual resistance is 441.6.
Test voltage is 21.68. 41ma. Or 1.06watts.
Are you sure your resistors are 1watt?
Attachment:
The attachment 20180320_125724.jpg is no longer available

Yes John:
To the extent I believe the box they came from and the physical size... Yes.

Attachment:
1watt.jpg
1watt.jpg [ 53.89 KiB | Viewed 1305 times ]

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Tue 20, 2018 11:06 pm 
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I see you are using carbon type. Maybe The type I used run hotter. Interesting. That's the only difference I can see.
Like the difference in heat when I switched to the sand type. I know the 10watt sand resistor is cool compared to the
5watt epoxy type.
I really don't know.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Tue 20, 2018 11:21 pm 
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john8750 wrote:
Peter- I put two 220ohm 1watt resistors in series. My test voltage is 28.61volts. Current draw is 65ma/1.85watts. There is no way I could even touch the resistors, certainly not hold them.

I did the same test with 28.6 VDC and .07 Amps using two 220 Ohm 1 Watt resistors in series and couldn't touch them after 30 seconds. Same resistor kit as Peter's.


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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Tue 20, 2018 11:30 pm 
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Mike Toon wrote:
john8750 wrote:
Peter- I put two 220ohm 1watt resistors in series. My test voltage is 28.61volts. Current draw is 65ma/1.85watts. There is no way I could even touch the resistors, certainly not hold them.

I did the same test with 28.6 VDC and .07 Amps using two 220 Ohm 1 Watt resistors in series and couldn't touch them after 30 seconds. Same resistor kit as Peter's.

But .07A x 28.61v is 2 full watts... right at the top of the rating.
I wouldn't try to hold a 2watt resistor with a full 2watts going through it either.

I'm using two 220 ohms = 440
But only 25v = .056A = 1.4watts

25v/440= .056A
.056A x 25v = 1.42 watts

No trouble holding that.

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 Post subject: Re: 6V6 amp project- with a twist
PostPosted: Mar Tue 20, 2018 11:47 pm 
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22.3V/60ma still too hot. 139° after 1 minute.

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