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    Is there a 12VDC source on the ST-120

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    bbqjoe
    bbqjoe

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    Is there a 12VDC source on the ST-120

    Post by bbqjoe on Mon Jan 07, 2019 7:25 pm

    I'm wondering just that.
    Is there anywhere on the St120 that I might tap into 12VDC?

    I'd like to have a computer fan in the general vicinity I can switch on when I, or it might feel the need.

    Thanks.
    tubes4hifi
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    Re: Is there a 12VDC source on the ST-120

    Post by tubes4hifi on Mon Jan 07, 2019 7:45 pm

    no 12vdc, but you could use the 6vac filaments and use a diode to give you around 8vdc to run a 12vdc fan
    bbqjoe
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    Re: Is there a 12VDC source on the ST-120

    Post by bbqjoe on Mon Jan 07, 2019 7:51 pm

    tubes4hifi wrote:no 12vdc, but you could use the 6vac filaments and use a diode to give you around 8vdc to run a 12vdc fan

    Thanks.

    Do you think 8vdc might be enough to run a chinatown 12vdc fan control board?

    What about on the SP14.

    There's a few unused wires there on the transformers. What's available there?
    tubes4hifi
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    Re: Is there a 12VDC source on the ST-120

    Post by tubes4hifi on Mon Jan 07, 2019 7:53 pm

    it should be, alot of people run fans at half rated voltage to lower noise and airflow
    bbqjoe
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    Re: Is there a 12VDC source on the ST-120

    Post by bbqjoe on Mon Jan 07, 2019 7:57 pm

    tubes4hifi wrote:it should be, alot of people run fans at half rated voltage to lower noise and airflow

    I edited while you posted.

    What's available on the unused wires on the SP14 transformers?
    tubes4hifi
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    Re: Is there a 12VDC source on the ST-120

    Post by tubes4hifi on Mon Jan 07, 2019 8:06 pm

    if you have a standard SP14 without the Khozmo remote, there is an extra 6vac winding on the larger B+ transformer
    bbqjoe
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    Re: Is there a 12VDC source on the ST-120

    Post by bbqjoe on Mon Jan 07, 2019 8:12 pm

    tubes4hifi wrote:if you have a standard SP14 without the Khozmo remote, there is an extra 6vac winding on the larger B+ transformer

    Beautiful!!!!

    Thank you.
    LeGrace
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    Re: Is there a 12VDC source on the ST-120

    Post by LeGrace on Mon Jan 07, 2019 8:19 pm

    I'm cooling my M125's with quiet 12v DC fans. To power them using a power supply I took out of a useless computer it was so old, plug and play.
    bbqjoe
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    Re: Is there a 12VDC source on the ST-120

    Post by bbqjoe on Mon Jan 07, 2019 8:26 pm

    LeGrace wrote:I'm cooling my M125's with quiet 12v DC fans. To power them using a power supply I took out of a useless computer it was so old, plug and play.

    Yeah, that's an option too.

    I just thought it might be less clutter without an extra power supply plugged in, especially since I'm in the midst of building an SP14 and it's still open and on the bench.
    There's enough room in there too that a little fan temp controller board would fit in just fine.

    I was just looking at something like this:


    https://www.amazon.com/Diymore-Temperature-Manumotive-Controller-High-Temperature/dp/B0752GMMPJ/ref=pd_cp_147_1?pd_rd_w=dyl1c&pf_rd_p=ef4dc990-a9ca-4945-ae0b-f8d549198ed6&pf_rd_r=FJ88FKK9AFZA4XY8FK25&pd_rd_r=cdea14aa-12d3-11e9-9525-1788c46d78d5&pd_rd_wg=5jLm9&pd_rd_i=B0752GMMPJ&psc=1&refRID=FJ88FKK9AFZA4XY8FK25
    erhard-audio
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    Re: Is there a 12VDC source on the ST-120

    Post by erhard-audio on Mon Jan 07, 2019 8:28 pm

    you could also use a simple voltage doubler circuit to get around 12VDC from 6.3VAC
    bbqjoe
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    Re: Is there a 12VDC source on the ST-120

    Post by bbqjoe on Mon Jan 07, 2019 8:34 pm

    erhard-audio wrote:you could also use a simple voltage doubler circuit to get around 12VDC from 6.3VAC

    Hmmmm.
    Guess I better go look for one of those too! lol!


    Easy enough!



    Last edited by bbqjoe on Mon Jan 07, 2019 8:40 pm; edited 1 time in total
    erhard-audio
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    Re: Is there a 12VDC source on the ST-120

    Post by erhard-audio on Mon Jan 07, 2019 8:38 pm

    here is a diagram



    If you need to drop it a bit, use a 2W resistor of the desired value to bring that 12.6VDC down a bit...
    sKiZo
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    Re: Is there a 12VDC source on the ST-120

    Post by sKiZo on Mon Jan 07, 2019 8:43 pm

    One concern might be introducing electrical noise into the circuit.

    PS - what makes you think you need a fan? Tube amps tend to run hot and can do so for decades without any problems.
    erhard-audio
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    Re: Is there a 12VDC source on the ST-120

    Post by erhard-audio on Mon Jan 07, 2019 8:45 pm

    sKiZo wrote:One concern might be introducing electrical noise into the circuit.

    PS - what makes you think you need a fan? Tube amps tend to run hot and can do so for decades without any problems.

    a good point re why a fan is needed...
    As to noise, using the circuit I posted there will be no noise.
    The only 'noise' would be mechanical and the like from the fan
    bbqjoe
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    Re: Is there a 12VDC source on the ST-120

    Post by bbqjoe on Mon Jan 07, 2019 8:54 pm

    My only concern is AZ heat in the summer.
    House is not embellished with AC.

    Maybe I don't need to concern myself with it.
    Dave_in_Va
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    Re: Is there a 12VDC source on the ST-120

    Post by Dave_in_Va on Mon Jan 07, 2019 11:14 pm

    I ran a small computer 12v fan inside of a Vox AC30 clone that got REALLY hot. I tapped off the 6.3 volts at the pilot light (connected to the heaters) and while it ran at half speed it was definitely moving enough air to cool down the amp.
    You don't need to move much air for tube cooling.
    LeGrace
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    Re: Is there a 12VDC source on the ST-120

    Post by LeGrace on Tue Jan 08, 2019 8:12 am

    When I had the amps out in the open on top of a cabinet I did not require fans. But people kept wanting to touch the tubes so I moved them inside the cabinet where temps skyrocketed. They now run cooler compared to when they were out in the open while acting as a great space heater for our chilly Canadian winters!
    bbqjoe
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    Re: Is there a 12VDC source on the ST-120

    Post by bbqjoe on Tue Jan 08, 2019 8:36 am

    My thought is this.
    Due to space constraints, I might end up placing the St-120 on top of the SP14, using some pucks or something for spacers.
    I think it wouldn't be a bad idea to have a computer fan or two circulating some air between them.
    They won't be enclosed in a cabinet though.

    But I can see for some, that tubes are like speaker cone dust caps, and people just can't help but want to touch them.
    peterh
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    Re: Is there a 12VDC source on the ST-120

    Post by peterh on Tue Jan 08, 2019 9:03 am

    bbqjoe wrote:I'm wondering just that.
    Is there anywhere on the St120 that I might tap into 12VDC?

    I'd like to have a computer fan in the general vicinity I can switch on when I, or it might feel the need.

    Thanks.
    If using Si rectifier the 5V winding is free to use. With a simple doubler you will have
    close to 12VDC available.
    bbqjoe
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    Re: Is there a 12VDC source on the ST-120

    Post by bbqjoe on Tue Jan 08, 2019 9:08 am

    peterh wrote:
    bbqjoe wrote:I'm wondering just that.
    Is there anywhere on the St120 that I might tap into 12VDC?

    I'd like to have a computer fan in the general vicinity I can switch on when I, or it might feel the need.

    Thanks.
    If using Si rectifier the 5V winding is free to use. With a simple doubler you will have
    close to 12VDC available.

    I Don't know from Si.
    I'm using a Weber WS1 rectifier.
    Or did you mean S1?
    Peter W.
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    Re: Is there a 12VDC source on the ST-120

    Post by Peter W. on Tue Jan 08, 2019 9:09 am

    The only concern I would have is the loading on the transformer.  The typical fan is about eight ( 8 ) watts, or roughly the same as four (4) 12**7s. Or two (2) 6SN7s.

    As these fans are motor loads, they will draw the same amount of current at any voltage sufficient to spin them. And if the voltage drops too low, eventually the motor will burn up.

    However, here is a 6 - 12V fan that draws less than 2 watts at 10 CFM that might do the trick. It is small at a bit more than 1.5 x 1.5 x 0.5 inches. But it may be enough.  

    https://www.cui.com/product/resource/cfm-40-series.pdf  

    For these fans to do any good, they should be mounted directly on the item to be cooled, ideally sucking out, not in. I write "Ideally" as if you are in a dusty environment, or have multiple cats, dogs and grandchildren running about, you will want the fan blowing in, and through a filter of some nature.
    peterh
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    Re: Is there a 12VDC source on the ST-120

    Post by peterh on Tue Jan 08, 2019 11:20 am

    bbqjoe wrote:
    peterh wrote:
    bbqjoe wrote:I'm wondering just that.
    Is there anywhere on the St120 that I might tap into 12VDC?

    I'd like to have a computer fan in the general vicinity I can switch on when I, or it might feel the need.

    Thanks.
    If using Si rectifier the 5V winding is free to use. With a simple doubler you will have
    close to 12VDC available.

    I Don't know from Si.
    I'm using a Weber WS1 rectifier.
    Or did you mean S1?
    The ws1 is a Si ( silicon) rectifier.
    You will have to disconnect the 5V winding from the rectifier tube socket and mount the two
    cables to a new solder strip mounted somewhere. On this strip you may also mount the
    new diodes ( 1n5004 ?) that the DC doubler is made of. You also need 2 electrolytic capacitors to
    the voltage doubler. When finished you will have 12-13V DC and about an amp capacity for
    your fan.
    bbqjoe
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    Re: Is there a 12VDC source on the ST-120

    Post by bbqjoe on Tue Jan 08, 2019 12:03 pm

    peterh wrote:
    bbqjoe wrote:
    peterh wrote:
    bbqjoe wrote:I'm wondering just that.
    Is there anywhere on the St120 that I might tap into 12VDC?

    I'd like to have a computer fan in the general vicinity I can switch on when I, or it might feel the need.

    Thanks.
    If using Si rectifier the 5V winding is free to use. With a simple doubler you will have
    close to 12VDC available.

    I Don't know from Si.
    I'm using a Weber WS1 rectifier.
    Or did you mean S1?
    The ws1 is a Si ( silicon) rectifier.
    You will have to disconnect the 5V winding from the rectifier tube socket and mount the two
    cables to a new solder strip mounted somewhere. On this strip you may also mount the
    new diodes ( 1n5004 ?) that the DC doubler is made of. You also need 2 electrolytic capacitors to
    the voltage doubler. When finished you will have 12-13V DC and about an amp capacity for
    your fan.

    Thanks.
    That's just a bit too much monkeying around for me, just to run a fan or two.
    peterh
    peterh

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    Re: Is there a 12VDC source on the ST-120

    Post by peterh on Tue Jan 08, 2019 12:12 pm

    bbqjoe wrote:
    peterh wrote:
    bbqjoe wrote:
    peterh wrote:
    bbqjoe wrote:I'm wondering just that.
    Is there anywhere on the St120 that I might tap into 12VDC?

    I'd like to have a computer fan in the general vicinity I can switch on when I, or it might feel the need.

    Thanks.
    If using Si rectifier the 5V winding is free to use. With a simple doubler you will have
    close to 12VDC available.

    I Don't know from Si.
    I'm using a Weber WS1 rectifier.
    Or did you mean S1?
    The ws1 is a Si ( silicon) rectifier.
    You will have to disconnect the 5V winding from the rectifier tube socket and mount the two
    cables to a new solder strip mounted somewhere. On this strip you may also mount the
    new diodes ( 1n5004 ?) that the DC doubler is made of. You also need 2 electrolytic capacitors to
    the voltage doubler. When finished you will have 12-13V DC and about an amp capacity for
    your fan.

    Thanks.
    That's just a bit too much monkeying around for me, just to run a fan or two.

    That could very well be a correct observation.
    To get a wall wart that delivers 8 - 12V DC would be much easier and you don't have to
    mess around with your amp.
    If you power the amp and wall wart from the same switched outlet you won't forget to turn
    the fan on or off.
    aguaazul
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    Re: Is there a 12VDC source on the ST-120

    Post by aguaazul on Tue Jan 08, 2019 1:45 pm

    These are great: Thermaltake Mobile Fan II External USB Powered Cooling Fan it even has a speed controller to cool quietly.

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    Re: Is there a 12VDC source on the ST-120

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