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Old 11th October 2011, 10:05 AM   #41
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Sir tony, i need help,
i want to rewind this traffo to 0-50 10 amp. can u help me?
the core size is9.6cm H, 8cm W and bobin lenght is5.2cm
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Old 14th October 2011, 02:41 AM   #42
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sir tony,
nice looking gears
almost complete,i bet your gear is better than trapo maker @ raon,
it was 2002 the last time i order 20 amp with 65-0-65 big trapo @ richland electronic center by that time it cost me 1,950php.
it was really big and my light flicker every time i power on that amp with that trapo,i already made power on delay for that one.
looking at your picture i guess it was a choke coil for a tube amp
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Old 14th October 2011, 03:48 AM   #43
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sir tony please help me with this coil
marshal superlead 100w
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Old 14th October 2011, 04:51 AM   #44
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choke coil
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Old 14th October 2011, 04:53 AM   #45
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here it says
3.3h
75ohms
Super Lead B+ Supply - MetroAmp Wiki
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Old 14th October 2011, 05:05 AM   #46
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can anybody agree with the
3.3h
75ohm
225mAmp
choke coil for 100w superlead
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Old 14th October 2011, 05:16 AM   #47
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Quote:
Originally Posted by engel dela pena View Post
sir tony,
nice looking gears
almost complete,i bet your gear is better than trapo maker @ raon,
it was 2002 the last time i order 20 amp with 65-0-65 big trapo @ richland electronic center by that time it cost me 1,950php.
it was really big and my light flicker every time i power on that amp with that trapo,i already made power on delay for that one.
looking at your picture i guess it was a choke coil for a tube amp

yes, the small ones are choke for tube guitar amps....if you want to roll you own, here is a good place to start: audiofilterchokes
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Old 14th October 2011, 05:25 AM   #48
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Quote:
Originally Posted by sandeep kayarkar View Post
Sir tony, i need help,
i want to rewind this traffo to 0-50 10 amp. can u help me?
the core size is9.6cm H, 8cm W and bobin lenght is5.2cm
sorry for late reply, your traffo is too small for 500watts, you should get a bigger traffo like a 1.75 inches center leg stacked to 3inches....
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Old 14th October 2011, 05:27 AM   #49
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Quote:
Originally Posted by engel dela pena View Post
can anybody agree with the
3.3h
75ohm
225mAmp
choke coil for 100w superlead
you can replace that coil with a 75ohm 10watt resistor and you won't even miss the choke....
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Old 14th October 2011, 07:18 AM   #50
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sir tony i been following this debate
this is from marshal amp forum about this choke
Resistor to choke switch question? - Marshall Amp Forum

Basically what happens is that you have a "ripple" coming from the rectifier circuit, which is basically the positive pulses from the transformer that the rectifier passed through while blocking the negative pulses. These pulses must be filtered into a constant voltage, which is the job of the filter caps.

The first stage filter caps that power the plates of the output valves filter out most of it, but you still have some by the time it gets to the choke. You don't hear it in the output section because 1/2 the output valves are running out of phase from the other half so the 120Hz ripple frequency gets cancelled out of the audio signal. But some of it is still there, which is why you have multiple filter sections in an amplifier.

As the ripple voltage rises positive, it causes a magnetic field to build around the choke coil as the voltage rises. When the voltage falls back toward zero, the magnetic field collapses around the coil and when it does, it induces a counter-voltage into the coil to pick the voltage across the choke coil back up. The voltage across the choke offsets the ripple voltage, thus eliminates some of the ripple.

It also provides a small amount of DC resistance (around 75-110 ohms) between the plate supply and the screen supply.

The "sag" resistor does not provide any filtering at all like a choke does because it is a "non-reactive" component. It does not build and collapse a magnetic field like a choke does. It only provides isolation between the plate and screen to prevent "intermodulation distortion" caused by the plate circuit of the output valves trying to steal current from the screen filter caps. Electrons from the screen filter caps will see the screen as the easier path as compared to having to flow through the sag resistor to get to the plate, and likewise for the electrons supplied by the first stage plate filter caps...they'll see the plate circuit as the easier path rather than the sag resistor and screens.

It is called a "sag" resistor because it is typically a higher value than the DC resistance of a choke. Due to its higher value, it exhibits a higher voltage drop to the proceeding stages more than the voltage drop of a choke as the amp circuitry pulls current through it, which we all know as "voltage sag", or simply "sag".

Advantages to running a choke over a sag resistor is for one, less voltage sag at the screens, phase inverter & preamp as well as more filtering provided by the choke that the sag resistor cannot provide, which will reduce the likelyhood of "ghosting" (i.e. where you hear "ghost harmonics/notes" around the fundamental/original note).

Randy, yes I would recommend switching the amp into Standby mode before making the switch between the sag resistor and the choke.
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