Salas hotrodded blue DCB1 build - Page 106 - diyAudio
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Old 24th May 2011, 09:05 AM   #1051
massimo is offline massimo  Italy
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A resistor when soldered on a board might be in parallel with another device and thus giving a different reading on the meter.
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Old 24th May 2011, 09:14 AM   #1052
Siberia is offline Siberia  Lithuania
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Just after posting a question, I realized it was a stupid one. Put it on a noob account.
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Old 24th May 2011, 08:28 PM   #1053
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Quote:
Originally Posted by Salas View Post
Good. Since you got the sinking, its OK to hot-rod further. Pictures?
--pictures to come, just need to get some time and I will definitely post some pics.

I measured 1.3v drop across the 10R resistor, using my 18-0-18 v R type transformer connected directly to the mains. Ultimately I will be powering the DCB1 from a balanced AC PS that has approx 210-220v. I also have a 15-0-15 transformer on hand to use if the higher output one does not work out.

I would like to tap 5-9v DC from this board to supply my switched relay volume control which is rated at 150ma. I tried to use a 30 ohm resistor in series with the LM7812 on the DCB1 but interfered with the relay operation. what would be the best way to obtain this extra voltage supply? I was going to add a 9v 78 series regulator, but hoped that you may have a more elegant solution.

I also found that all the LEDs illuminated on the PCB with only one half of the transformer connected and the DCB1 seemed to work well on 1/2 of the supply.

Brad
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Old 24th May 2011, 08:38 PM   #1054
Salas is online now Salas  Greece
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The drop across RcurrentSet has to do with the Vf of the 3 leds minus the Vgs of the CCS Mosfet. The most productive is you arrange the I=V/R via proper R value to target I than changing leds or Mosfet. Vgs will also differentiate for different currents a little.

I would nick just after the rectification, tapping off the filter cap to a 3 legged chip for the sub circuit needed. Don't overload the 7812 (you saw the result).

That with the illuminated leds was by using one secondary across the Tx connector I suppose, not middle and next inserts.
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Old 24th May 2011, 09:12 PM   #1055
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I've found the source (partial?) of that horrible sound. Kinked interconnects. Cables were loosely soldered to connectors. The sound is not bright at all at the moment, but the lower region is still uninvolving.

I'm looking at B1 schematics, but being amateur I am, I can't undertand what two of 220R are parallel to.
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Old 24th May 2011, 09:19 PM   #1056
Salas is online now Salas  Greece
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Referring to the input or output 220R?
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Old 24th May 2011, 09:27 PM   #1057
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I guess, the output ones. Goegraphically two ones in the middle of all four 220R resistors on DCB1 PCB.
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Old 24th May 2011, 09:40 PM   #1058
Salas is online now Salas  Greece
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If you measure a circa 7.2mA 170BL across D to S pins using the Ohm meter function of your DMM you will find circa 43R RDS. There is no extra source resistor(s) in the B1. So 220Ri+43RDS=263R. This one goes closing to earth for DC both ways, paralleling Ro. RDC=(263*220)/(263+220). 57860/483=119.79.
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Old 24th May 2011, 09:49 PM   #1059
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Thanks, that explains the values I'm getting.
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Old 24th May 2011, 09:50 PM   #1060
Salas is online now Salas  Greece
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Quote:
Originally Posted by johnwmclean View Post
I’ll double check my boards tonight, from memory two of my texas 220R resistors measured 120R in circuit and 220R before installation.
I thought I may have fried them too, but I have two DCB1 boards with exactly the same components to verify ie both resistors measured the same (120R) in circuit on each board.
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Originally Posted by Siberia View Post
I'm very interested in your double checking. What's the explanation behind this resistance change then?
Those are correct for the DC realm.
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