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Old 19th September 2012, 11:11 AM   #3161
Salas is offline Salas  Greece
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When having say 300V and someone has a hot sink already because of limited space in an assembly for just the 20mA allowance he better not let it open burn say another 50mA that was allocated to the load for long. The shunt has the same functional blocks as the LV ones. Its a matter of space and thermal economy. If they like they can use sinking for full dissipation in long term open circuit event. Above all don't stress circuitry or play hard testing if not sure and experienced when on HV is my angle to the many builders especially those not in experience with HV regs. Messing with HV to a minimum keeps us safer.
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Old 20th September 2012, 12:33 AM   #3162
tubo is offline tubo  Philippines
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Hi guys,

Pls point me where i could find a pcb or a kit if they are available.. Thanks very much
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Old 20th September 2012, 07:07 AM   #3163
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Salas View Post
When having say 300V and someone has a hot sink already because of limited space in an assembly for just the 20mA allowance he better not let it open burn say another 50mA that was allocated to the load for long.
But I am talking about designing for survivability.
Hot during normal operation could be 60C.
If the output did become open circuit the amplifier would turn off in some way indicating a fault.

During the time it takes to think about the problem (and maybe power down) the sink is increasing in temperature aiming for the worst case. That could be 100C, more or less. What I would want is no damage during this episode.
What most builders would not want is for the Shunt to damage it's self during this mishap.
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Old 20th September 2012, 11:44 AM   #3164
euro21 is offline euro21  Hungary
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Originally Posted by tubo View Post
Hi guys,

Pls point me where i could find a pcb or a kit if they are available.. Thanks very much
GB for Salas SSHV2 regulator
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Old 20th September 2012, 02:47 PM   #3165
Salas is offline Salas  Greece
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Quote:
Originally Posted by AndrewT View Post
But I am talking about designing for survivability.
There is IRF840 designed in which is a 1C/W RthJC 125W @ 25C device. TJ=125C. Gives plenty of room for survivability to be mainly a matter of its sinking and ambient temp. Can't recommend a certain sink for all because of the wide voltage and mA range in this variable HV regulator. Also the extra current allowance is down to user's content bar the 20mA baseline, makes it an even wider sinking choice. I would give an idea with a broad example. If burning about 6W normally and there is about 40C ambient not that near to tubes or in box, a 2C/W sink will pass for 15W when no load is connected. Better not for too long because it will up the ambient also if in a box.
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Old 20th September 2012, 04:52 PM   #3166
AndrewT is offline AndrewT  Scotland
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I expect every Member /Builder to eventually have learned the skills of sizing a heatsink for them selves.
As you already know I do not suffer lazy Members gladly.

I expect them to do the Homework for their Project. If their Project is not important enough to deserve the learning effort, then in my book they are in the wrong hobby. DIY really does mean do it yourself.
Not:
"I want to build a modified version this week, give me the recipe, btw, I will change my demands for Forum support and ask for a new recipe next week/month."
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Old 20th September 2012, 05:04 PM   #3167
Salas is offline Salas  Greece
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Because this application is mainly addressed to tube equipment builders used in direct to air glass convection there could be less average familiarity with sinking and semis for genuine reasons.
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Old 25th September 2012, 03:00 AM   #3168
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Default Do I need a transformer?

I need 300vdc Vout from my Salas HV Reg.
Just out of interest (as I have 230vac mains), why do I need an expensive transformer to get the desired dc input volts to the reg, as my mains 230vac rectified will be approximately 320vdc which is the specified 20vdc higher than my Vout target.
So, do I need a transformer?

Thanks
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Old 25th September 2012, 03:06 AM   #3169
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one word... ISOLATION!
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Old 25th September 2012, 03:38 AM   #3170
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Ah, OK, been doing a bit of reading on safety aspects of using a transformer - thanks.
I've have got an isolating transformer that I use for my power tools so I might use that to try-out the reg.

Quote:
Originally Posted by kstlfido View Post
one word... ISOLATION!
Quote:
Originally Posted by marcus1 View Post
I need 300vdc Vout from my Salas HV Reg.
Just out of interest (as I have 230vac mains), why do I need an expensive transformer to get the desired dc input volts to the reg, as my mains 230vac rectified will be approximately 320vdc which is the specified 20vdc higher than my Vout target.
So, do I need a transformer?

Thanks
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