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Old 31st January 2011, 12:30 PM   #10191
Marra is online now Marra  United Kingdom
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Sorry Andrew that did't work right; I'll try and do the link later.
I am using an 500VA transformer feeding +- 132,000uf through schottky diodes.
The nuisance fuse blowing I will check out tomorrow as I have to go out now.
Thanks Marra.
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Old 31st January 2011, 12:42 PM   #10192
Marra is online now Marra  United Kingdom
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Hi Andrew do I take it that as you did not pass comment regarding the resistance readings for the mosfets that they are ok?
Marra
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Old 31st January 2011, 12:51 PM   #10193
AndrewT is offline AndrewT  Scotland
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500VA would normally use a T6A fuse to survive repeated start ups over the years.
With a soft start you can probably use an F2A if the resistor/s reduce the starting current sufficiently.

To use an F1A, I suspect you would need 3 CL60 in series and another 50r of Power Resistors to reduce the start up current and gradually bring it on line as the CL60s heat up.

With +-132mF you may want to consider slow charging. NTC are best for this, located in the secondary circuit and again bypassed when the CL60s have done their job.
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Old 31st January 2011, 01:28 PM   #10194
Zen Mod is offline Zen Mod  Serbia
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relays.......in secondary circuit ?

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Old 31st January 2011, 01:43 PM   #10195
anilva is offline anilva  India
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Andrew,

I if were to add a input capacitor to the F5 to prevent inadvertent DC to creep into the amp, is a 1 mfd, MKP a good choice, without compromising the bandwidth of the amp too much?

Thanks in advance.
Just to clarify, I am asking if a 1uf mkp is a good capacitor value to block dc input to the f5. I am assuming 101k as the 'R' value of the input. I am not sure if 1/(2*pi*r*c) is the right way to calculate the high pass frequency for this setup.

TIA.
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Old 31st January 2011, 01:48 PM   #10196
cviller is offline cviller  Denmark
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Originally Posted by Marra View Post
Yes this is without the bulb connected. On the left channel P1 does not alter the reading across the source resistor. P2 I can adjust. I raised the voltage to 0.12V and the offset changed so I turned it back to its lowest setting. With the right channel connected the p/s voltage started to rise then the 1amp q/b fuse popped.
Hi Marra, this is most likely your problem. You need to adjust both P1 and P2 - don't just turn one of them all the way to the end. Don't worry too much about DC before you have the current dialled in on the .47 ohms.
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Old 31st January 2011, 01:59 PM   #10197
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Quote:
Originally Posted by Zen Mod View Post
relays.......in secondary circuit ?
My fote vor wet fingertips.
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Old 31st January 2011, 02:31 PM   #10198
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und meine euch ......

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Old 31st January 2011, 04:06 PM   #10199
Marra is online now Marra  United Kingdom
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Thanks for the responses.
Andrew regarding the soft start I don't think theres any point in posting a link as there is no circuit diagram just pics of the pcb. I have been using one of these s/s in my Aleph 5 clone for the past 6yrs without any problem supplying 300VA transformers feeding +- 47,000uf per channel and a 2A slo/blo fuse.
Christian on one channel I adjusted P1 almost fully upwards without any voltage reading across the source resistor; P2 slowly raised the voltage upwards. The right channel when connected with the left disconnected blew the fuse. I was using a 1amp fuse which is what it says in the original article but having reread the article I realise it was advised in conjunction with a variac whereas I just turned the amp on. I guess I need to borrow a friends variac or try it with the reccomended 1.25amp slo/blo and see what happens.
Thanks again Marra
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Old 31st January 2011, 04:32 PM   #10200
Zen Mod is offline Zen Mod  Serbia
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you must iteratively turn one then other trimpot ;
while doing that - monitoring both - voltage across one source resistor and output offset .

while waking up one mosfet - other one is still sleeping , so current which can go through awaken one , have no possible path through other one ;

you wrote that you read powering up procedure .
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