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Author Topic: FAO - Oliver re: ramped 48v circuit for V series modules  (Read 5766 times)

RMoore

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FAO - Oliver re: ramped 48v circuit for V series modules
« on: January 02, 2005, 07:04:54 pm »

  Hi Oliver - I just saw the thread: 'Fletcher, have you tried the new Tab-Funkenwerk V-78?'

< for each V module you need a separate +48V ramped circuit (that can be feed from a main supply), sure most V units make it about a year or so without, but as soon as you hear slight crackling, loss of low and/or high end, you have a compromised input x-former. The circuit posted works quite well, is fairly cheap (about $5 in parts) and also takes care of the nasty pop you get if applying +48V. To be precise you need a at least 55V supply so the regulator works properly.

I had several heated arguments with hard core EE that +48V is absolutely save, etc. , but that again everybody send me the broken stuff as soon as it breaks for rewinding and complains about the cost. Take some time for preventive maintenance.... >

Thanks for the info & your ramped phantom circuit diagram,

Question: should it be possible to fit this circuit into an existing V series rack, assuming there's enough physical space?

Thanks again!

Ryan Moore

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RMoore

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Re: FAO - Oliver re: ramped 48v circuit for V series modules
« Reply #1 on: January 02, 2005, 07:27:11 pm »

BTW - thats great you are being a guest host here,
thnx in advance!
RM
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People's Republic of Ryan

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By the end of today, another day is gone forever. You will never get it back.
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Oliver Archut

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Re: FAO - Oliver re: ramped 48v circuit for V series modules
« Reply #2 on: January 03, 2005, 01:29:58 am »

Hello Ryan,

you can and should retrofit any U/V module or better historic gear with this circuit in case you use +48V.

This year alone I rewound several V72/76 an 77 input x-former that had an electric short, all customers described the problem the same, first a crackling noise than, loss of low end, all in conjunction with 48V use.

Rewinding is a pain in the butt job and quite expensive, the parts are only a few bucks and can save a lot...

Attached is a pic of a bad input , taken while switching 48V on, please see the small arc in the high lighted area....

Pleasure to be here!

Best regards,
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Oliver Archut
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RMoore

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Re: FAO - Oliver re: ramped 48v circuit for V series modules
« Reply #3 on: January 03, 2005, 05:20:25 am »

Hi Oliver - Ok, thanks..so theres hope,
Seems like blowing up the xformers is a situation to be avoided!
All the best,
Ryan
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By the end of today, another day is gone forever. You will never get it back.
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permeke

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Re: FAO - Oliver re: ramped 48v circuit for V series modules
« Reply #4 on: January 07, 2005, 07:45:33 pm »

Is that correct ?
Is this a 24V regulator ? (LM2824) to put after the regular 48V P ?
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Oliver Archut

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Re: FAO - Oliver re: ramped 48v circuit for V series modules
« Reply #5 on: January 07, 2005, 08:05:14 pm »

Hello Permeke,

an 24V voltage regulator modified with a 24 zehner diode reference will put out 48V. Please be sure to understand that the ma.x current and wattage rating will be reduced, but a 500mA regulator will work on 15mA phantom (dead short) without a problem.
There are several different variations, lots of room to play and modify...

Best regards,

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Oliver Archut
www.tab-funkenwerk.com

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Radd 47

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Re: FAO - Oliver re: ramped 48v circuit for V series modules
« Reply #6 on: January 07, 2005, 09:27:02 pm »


Hey Ollie, do we need a ramp down circuit also or just ramp up?
Also, do your current V series transformers need the 48 volts to be ramped?

Also, what is meant by your "soft ground " switch?
Is this just a resistor to ground type of deal? 100 ohms or something?


Thanks!
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Oliver Archut

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Re: FAO - Oliver re: ramped 48v circuit for V series modules
« Reply #7 on: January 07, 2005, 11:24:14 pm »

Hello Radd47,

thanks for pointing out the typo...

Thanks to Teflon, and Mylar the insulation resistance of the in production V-series x-former is several times higher than the historic ones. However a ramped circuit is employed to protect the tube after the x-former...

The historic as well as the new V modules have a 0V layout that is isolated from the chassis/PE ground, this can be switched either 0V to ground or via a 100 Ohm resistor to avoid 99% of all hum, RF noise etc. Even with the worst possible grounding you get the best noise floor possible...  
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Oliver Archut
www.tab-funkenwerk.com

We are so advanced, that we can develop technology that can determine how much damage the earth has taken from the development of that technology.

markus

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Re: FAO - Oliver re: ramped 48v circuit for V series modules
« Reply #8 on: January 10, 2005, 05:38:28 am »

so did i get this right - an external phantom power unit will also not work?
i've got a sennheiser external 48v supply i want to put between my mic (at 4047) and my v72. does it put 48v on the outputs as well?
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Oliver Archut

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Re: FAO - Oliver re: ramped 48v circuit for V series modules
« Reply #9 on: January 12, 2005, 12:54:20 am »

Hello Markus,

it has been quite a while since I use an external P48 supply, the last ones I checked had a blocking cap to decouple, but if you switch it on, there is still the charging time of the caps that draw a current primary to core, so you still have (maybe reduced) problem. Talk to your local tech, he should be able to help you out with a ramped mod...

Best regards,

Oliver
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Oliver Archut
www.tab-funkenwerk.com

We are so advanced, that we can develop technology that can determine how much damage the earth has taken from the development of that technology.
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