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Old 10th April 2009, 09:50 PM   #5951
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Default Funkyx2... you are welcome



ask all you want and all you need....and also read the entire thread... use Greg Erskine home pages.... a wonderfull helping hand.

All you may need is there... a rich collection of informations kindly offered by Greg Erskine (Gerskine in our forum)

http://users.tpg.com.au/users/gerskine/dxamp/

regards,

Carlos
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Old 10th April 2009, 09:53 PM   #5952
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Default Boys.... TRUST amplifier is now into Greg Erskine home page


Thank you dear Greg.

Many thanks!

regards,

Carlos

http://users.tpg.com.au/users/gerskine/dxamp/
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Old 10th April 2009, 10:21 PM   #5953
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Default The last movies made are all here.


Dx Corporation is the only one offers you movies too!

http://www.youtube.com/watch?v=w3QphsVZm0Q

http://www.youtube.com/watch?v=dodhQmsx4qQ

http://www.youtube.com/watch?v=Du6Gv2-46DQ

http://www.youtube.com/watch?v=6nh85mMARZQ

Please, visit those adresses.... i have made all this to you!

regards,

Carlos
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Old 11th April 2009, 01:35 PM   #5954
funky2x is offline funky2x  Syria
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HELP ...... HELP ...... HELP
Yes , am following Greg website instructions on adjusting the DX bias, and trimming DC offset
I measured 11.2 volts around the protective resistor on the positive rail with the trim pot on 1 kohm ( turned to the max ) .
and when turning the trim pot lower the voltage go higher
I didnt complete the adjusting cus something wrong .
I will double check the circuit board and soldering joint and the transistors , Anything else ?




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Old 11th April 2009, 03:13 PM   #5955
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Default Take it easy.... relax because things are better than you can imagine


Your bias trimpot is adjusting...this seems the circuit may be fine...some differences in transistors, resistances, some minor errors can cause this.

Try, in advance..as first try, to include a resistance in series with your trimpot.... place a 330 ohms for instance..or 220ohms if you have it...can be even 390 ohms,.

It is normal when you reduce the bias trimpot resistance to obtain increasing in current...so...your bias trimpot is operating...this means bias circuit is fine and bootstrap resistances are too..and also VAS transistor is conducting.

In advance to check the all stuff...try to include and try to adjust once again.

I hope this voltage is over 10 ohms resistance..because if not.... everything will be different...current is the result of the division from the voltage you have measured by the resistance you are using...so.... 1 Volt into 10 ohms means 100 miliamperes (0.1A) and this is acceptable!!!..better if you find 600 milivolts or less, and over 10 ohms resistance.

11 Volts means more than one ampere... this is too much!

Relax man... everything gonna be all rigth..i am here...and never fear when Charlie is here.

regards,

Carlos
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Old 11th April 2009, 03:16 PM   #5956
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Default I think you are talking about the Dx Amplifier, the Dx Standard


the one (the main one) we are exploring in this thread.

here you can see a simulation with the trimpot into 1K... you see the current value.... this means some resistance you're using is diferent than the standard value..or some transistor gain.... but relax... soon you will find the guilty.

If the 330 ohms resistance inclusion did not satisfy..them go checking all amplifier... measure all resistances.

regards,

Carlos
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Old 11th April 2009, 03:30 PM   #5957
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Default When you increase the bias trimpot resistance


You will have more voltage drop over this resistance... this means base to emitter voltage willl increase.... when this voltage increases, the resistance from colector to emitter decreases...decreasing the colector to emitter resistance the voltage drop from colector to emitter also decreases.. this will produce less drive voltage to the output transistors, as a result they will conduct less..current will be reduced.

When you decrease the bias trimpot resistance, you gonna have less voltage drop over this resistance..and this have as result the reduction of base to emitter voltage... reducing the base to emitter voltage you gonna have increasing into the colector to emiter resistance.... this increase in resistance will cause an increase of voltage drop from colector to emitter...this increase in voltage will drive the output transistors more.... and this will cause more current consumption.

So... reducing the bias trimpot resistance, in this circuit, you gonna have more current into the output stage....and increasing the bias trimpot resistance will result in less current into the output stage.

Circuit is the published as standard...a NPN transistor... a 2K2 resistance from colector to base and a 1K variable resistance, a trimpot, from base to emitter..and this one, as standard to start adjustments, must be pre set measuring 750 ohms resistance.

This is good to almost all cases..but depends the bootstrapp current, also how driven is the VAS transistors..the transistors gain and the supply voltage.

regards,

Carlos
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Old 11th April 2009, 06:41 PM   #5958
funky2x is offline funky2x  Syria
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Thank you , Thank you , Thank you which isnt enough for being you here to help .
the Guilty was TIP 42 , short transistor and now am playing the DX amp with the volume almost all the way Up high and soon I need to get a new glass for the windows here in my room .
Deep bass .
But , on the PSU used with the amp , Two leds for indication .
the one on positive rail turn off faster than the one on negative rail .
will do some more checking but now on the psu and capacitors .



DX playing in Syria .
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Old 11th April 2009, 07:28 PM   #5959
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Default Oh!... very good...so Siria is your place?


I was trying to discover, clicking into the flag and could not.

There's some way to discover but i could not remember how to do it clicking into the flag.


I am glad you are happy with your amplifier.

You have a sensitivity adjustment.... into the second differential transistor you have a 2K2 resistance connected to the base... reducing it you gonna have more sensitivity, needing less volume into the input to force the amplifier enter distortion (real full power).... increasing it you gonna have less sensitivity.

Full power must enter distortion...so... it seems your resistance is not fine to your audio source output level.

I am glad you have apreciated.

Dx Corporation send you the most warm thanks by your preference, and congratulates you because you could assemble it fast and almost no significative errors.

regards,

Carlos
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Old 12th April 2009, 01:15 AM   #5960
funky2x is offline funky2x  Syria
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Am using 22Kohm for attenuator at the input .
is that ok or not ?





just for fun , a very dangerous vehicle , dont try
4x4
7000 cc
......
Etc
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