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measuring current across diodes

Posted 6th March 2010 at 03:09 PM by klewis

Do you know what is the Vf of your LEDs? R1 should be roughly equal to (3 x Vf) / desired_current. So for testing, if your LEDs have Vf = 1.8V or even Vf = 2.1V, and we're aiming for something around 20mA, then you can use R1 = 300R.

For 1.8V LED
I = 3 * 1.8 / 300 = 18 mA

For 2.1V LED
I = 3 * 2.1 / 300 = 21 mA

The 300R resistor can be 1/2W or whatever you have around.

You will know it works well if you measure the voltage across R1 and divide it by 300 and if the result is close to about 20. Of course you should see the LEDs on.

Try to implement just the CCS portion with a 300R for R1.
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Old

testing Mosfets and BJT for shorts

Posted 6th March 2010 at 03:07 PM by klewis

http://www.4qdtec.com/mostest.html

and for BJTs, diodes and zeners

http://www.hobby-hour.com/electronic...conductors.php
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Old

how to test CCS for shunt

Posted 6th March 2010 at 03:02 PM by klewis

the following link explains
http://www.diyaudio.com/forums/power-supplies/143693-simplistic-salas-low-voltage-shunt-regulator-200.html#post2108791
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Old

DIY adventures

Posted 4th March 2010 at 10:26 AM by jtktam (Newbie audio DIYer)

It's been fun to do simple head amps (RA1 clones) and chip amps (audiosector, chipamp.com) and then move onto 4 chip TDA boards off ebay into big heatsink chassis

Along the way I learned a lot about sourcing parts (a pain), chassis work (bigger pain) and component layout for optimal cable distance and distortion

My last finished project, the b1 buffer, was the best result so far.. it's simple, but it blew away my friends big name preamps.. enough that they are making a shift to DIY their own!

Time is a commodity that a lot of DIYaudio guys lack.. other responsbilities means we have very little time to devote to projects we start and a lot of times projects get drop to the wayside.

My latest project is the F5 and I hope to get it done by the next burning amp meet.. I want to see if I can convince papa to autograph that and the B1
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Old

Stereo and TV

Posted 1st March 2010 at 05:53 PM by JamesTRexx

2010/03/01; removed the unused Rotel amplifiers and re-arranged the rack. Looks much better now.
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Old

Nelson Pass Interview

Posted 23rd February 2010 at 06:05 PM by jan.didden
Updated 3rd November 2010 at 09:38 PM by jan.didden (fixed broken link)

My interview with our own Nelson Pass appeared in MultimediaManufacturer.
Read it here: http://www.linearaudio.nl/interviews/np.pdf
jan didden
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Old

F5 discussions

Posted 23rd February 2010 at 05:57 PM by jtktam (Newbie audio DIYer)

http://hifi4sale.fullboards.com/equi...-amp-t2455.htm
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Old

B1 Buffer BOM

Posted 23rd February 2010 at 05:54 PM by jtktam (Newbie audio DIYer)

2SK370 N channel JFET Transistor 4x (GR or BL grades)
1N914 Diode
Generic LED
15000 uF 2x Electrolytic 25v
10 uF 2x Film
1 uF 3x Film
1 ohm 3w
1k ohm 4x .25w
10k ohm 2x .25w
15k ohm .25w
25k ohm 2x .25w
221k ohm 2x .25w
1M ohm 6x .25w
2 way switch
RCA jack 6x
Linear Taper Pots 25k 2x
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Old

F5 bom

Posted 23rd February 2010 at 05:49 PM by jtktam (Newbie audio DIYer)

R1 - R2 2 10R 10R - 1% - 0.6W
R3 - R4 - R15 - R16 4 2.2K 2.2K -1% - 0.6W
R5 - R6 - R7 - R8 4 100R - 3W 100R - 3W
R9 - R17 - R18 3 1K 1K - 1% - 0.6W
R10 1 100K 100K - 1% - 0.6W
R11 - R12 2 0.47R - 3W 0.47R - 3W
R13 - R14 2 47R 47R - 1% - 0.6W
R19 - R20 2 150R 150R - 1% - 0.6W
R21 - R22 2 10K to 22K (same value !) 10K to 22K - 1% - 0.6W
P1 - P2 2 5K Trimmer Vishay 64W/Bourns 3296 - 5K - 25 T
Q1 1 2SK170-BL (2SK370) N - Matched Idss
Q2 1 2SJ74-BL (2SJ108) P - Matched Idss
Q3 1 IRF9240P/FQA12P20 P - Matched Vgs
Q4 1 IRF240N/FQA19N20C N - Matched Vgs
Q5 1 ZTX550 (BC560) Zetex or similar - PNP
Q6 1 ZTX450 (BC550) Zetex or similar - NPN
TH1 - TH2 2 4.7K 4.7K - NTC - Thermistor - 3980K
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Old

Pd f5

Posted 23rd February 2010 at 05:47 PM by jtktam (Newbie audio DIYer)

http://www.diyaudio.com/forums/pass-...ml#post1740824
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