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Old 14th February 2012, 02:26 PM   #1631
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Thanks. Im not quite sure where the cable came from....Its silver plated copper from a source I have forgotten long ago. It works great for stuff like this; but the teflon coating is somewhat difficult to strip in the smaller gauges.
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Old 14th February 2012, 04:01 PM   #1632
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Quote:
Originally Posted by albertli View Post
Rod,

Many thanks for your detail reply. Lucky I ask the way to test the filament, or otherwise I would directly series the 1.5R to ground. I have 10 pcs 100R 5W wirewound parallel, but end up it's only around 9R. I got 10R with only 9 pcs parallel together, but there is only 45W. Which way I should go ?
After the rectifier, my intention is 10,000uf - 25H - 30,000uf floating to the main chassis - your reg. then to ground. Would like to have your idea.

Albert
Hi Albert, For the choke, I assume you mean 25mH (milliHenry). That's OK. 4700uF is enough for C1, but 10000uF will be OK. 4700uF is better though, because the current pulses will be lower.

10R 45W should be fine, try it with this first! Make sure that the resistors are high quality though, no skimping. This is no place for White Ceramic Coffins! At least Welwyn W24 wirewound, vitreous enamelled. Andy has done lots of testing, see posts from last year.

.
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Old 14th February 2012, 05:19 PM   #1633
massimo is offline massimo  Italy
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Vishay/Dale HLM miniature flat wirewound resistors are the ones suggested by Andy
10ohm/20watt are easily avalable on eBay. 4pcs parallel/series connected et voilą, you got a perfect 10ohm/80watt resistor.
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Old 14th February 2012, 05:31 PM   #1634
euro21 is offline euro21  Hungary
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Mouser, Vishay/Dale 10Ohm 55W only 6.58 USD.

HL05509Z10R00JJ Vishay/Dale Wirewound Resistors - Chassis Mount

10 Ohm 95W 17.70USD

HL09509E10R00JE Vishay/Dale Wirewound Resistors - Chassis Mount
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Old 15th February 2012, 03:36 AM   #1635
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For the choke, I assume you mean 25mH (milliHenry). That's OK. 4700uF is enough for C1, but 10000uF will be OK. 4700uF is better though, because the current pulses will be lower.

Yes, there was a typo mistake, a 25mH to be exact. I don't have couple 4700uf/35v, but will source them for sure.

10R 45W should be fine, try it with this first! Make sure that the resistors are high quality though, no skimping. This is no place for White Ceramic Coffins! At least Welwyn W24 wirewound, vitreous enamelled. Andy has done lots of testing, see posts from last year.

There are all Dale CW-5 in Black and from the same supplier Andy post on the thread.
Thanks

Albert
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Old 15th February 2012, 03:38 AM   #1636
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Thanks and will try tweaking on after firing up.
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Old 15th February 2012, 07:19 AM   #1637
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Albert,

Please take the 25mH choke and measure the dc resistance with a meter. This value may need to be subtracted from the Resistor between C1 and C2 (2 ohm).
25mH may well measure 0.5 ohm or so - and mean that the 2-ohm should be 1.5.

Both R1 and R2 resistors are needed, even when the choke is used.

.
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Old 15th February 2012, 02:20 PM   #1638
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[QUOTE=Rod Coleman;2907329]Albert,

Please take the 25mH choke and measure the dc resistance with a meter. This value may need to be subtracted from the Resistor between C1 and C2 (2 ohm).
25mH may well measure 0.5 ohm or so - and mean that the 2-ohm should be 1.5.

Both R1 and R2 resistors are needed, even when the choke is used.



Rod,

The resistance is 0.4 ohm. So I should put the choke right after/ series to the rectifier then to C1 - 1.5 ohm - C2.
Regards

Albert

BTW I replaced the R8 to 470 ohm and C1 to 33uf /50v on the supply board. Is 33uf good for the job/ or I should keep the value 47uf ??
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Old 15th February 2012, 02:55 PM   #1639
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Use the 25mH in series with the R2 position (shown on the PSUD2 schematic, above). Not at the rectifier.

If the board has 47uF/35V - that is best.
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Old 16th February 2012, 04:09 AM   #1640
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Originally Posted by Rod Coleman View Post
Use the 25mH in series with the R2 position (shown on the PSUD2 schematic, above). Not at the rectifier.

If the board has 47uF/35V - that is best.
Rod,

On #1627, I presume R1 is the 25mH choke I talked about, R2 would then be 1.5 ohm.
I don't have 47/35v. I have some 100uf/25v, 56uf/25 or I can parallel one more 33uf/50v to make it 66uf/50v. What do you recommend ??

Albert
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