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Old 10th October 2009, 11:51 AM   #41
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Default The back side, the transistor's back metal plate used not to be flat

this results the parts you see as copper colour are the parts are alike mountains and they would touch the heatsink..the lower parts, the valleys, the deep parts are the ones not touched by the waterproof, grain 500, sandpaper

The sandpaper was placed over a flat surface, a glass plate..and then i move the transistor to erode till turn it flat..you see material was removed into the parts you see copper...now it is flat.

If you do not do that, then the parts are higher, the projections, to the metal bubbles, the peaks, the hills, the mountains into the metal surface, will be the ones will touch the heatsink..this will reduce (a lot) the heat transference.

Check your transistors..you gonna be very surprised.

regards,

Carlos
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File Type: jpg Actually the brass colour touches the heatsink.jpg (211.4 KB, 200 views)
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Old 10th October 2009, 02:20 PM   #42
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Default Now, some circuit details

Dx Amplifier – bass unit – to work with 62 plus and 62 volts minus

Was made (adjusted, tuned, tweaked) to work from 1 hertz to 300 hertz (-3dB)

Sensitivity – 1 volts rms to full rated unclipped output. (39.75 Volts rms)

Input impedance – 39K

Output impedance – 8, 6, 4, 2 and 1 ohm.. depending the quantity of power
transistors used into the output

Power amplifier details with sinusoidal input signal, and delivering 39.75 volts to
the load:

197 watts rms at 8 ohms, 200 Hz input with 1 volts rms of level, rail current
2.26A, and supply voltage at 62 volts to each one of the rails.

263 watts rms at 6 ohms, 200 Hz input with 1 volt rms of level, rail current
2.98A, and supply voltage at 62 volts to each one of the rails.

395 watts rms at 4 ohms, 200 Hz input with 1 volts rms of level, rail current
4.48A, and supply voltage at 62 volts to each one of the rails.

790 watts rms at 2 ohms, 200 Hz input with 1 volts rms of level, rail current
8.90A, and supply voltage at 62 volts to each one of the rails.

1135 watts rms, 1 ohm, 200 Hz input with 1 volts rms of level, rail current
14.9A, and supply voltage at 62 volts to each one of the rails.

regards,

Carlos
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Old 10th October 2009, 02:30 PM   #43
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Default About fuses and electrolitic condensers to the supply

About rail fuses and supply fuses… do not use fast blow

Operating with 8 ohms speakers, then use 2.5A fuse to each rail
and 5 ampere fuse in series with the output (speaker)

Operating with 6 ohms speakers, then use 3.0A fuse to each rail
and 6 ampere fuse in series with the output (speaker)

Operating with 4 ohms speakers, then use 5.0A fuse to each rail
and 10 ampere fuse in series with the output (speaker)

Operating with 2 ohms speakers, then use 10 A fuse o each rail
and 20 ampere fuse in series with the output (speaker)

Operating with 1 ohm speaker, then use 15A fuse to each rail
and 30 ampere fuse in series with the output (speaker)


About filter electrolitic condensers to the power supply

Operating with 8 ohms speakers, then use 12.500uf each rail
Operating with 6 ohms speakers, then use 15.000uf each rail
Operating with 4 ohms speakers, then use 20.000uf each rail
Operating with 2 ohms speakers, then use 50.000uf each rail
Operating with 1 ohm speaker, then use 100.000uf each rail

regards,

Carlos
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Old 10th October 2009, 02:43 PM   #44
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Default Continuing describing the power amplifier

Continuing with the specifications and details

The off set (Dc milivolts present into the output terminals due to
unmatching of transistor devices) is adjustable tweaking the 4k7
trimpot, pré adjusted to 3900 ohms (R23)..of set will be around
1.2 milivolts

Current crossing each power transistor is measured monitoring
voltage Dc, milivolts range, directly picking the voltage into the
emitter resistances extreme leads (0.33 ohm)… the voltage
to be measure may be 656 microvolts..and this results into 1.98
miliampere of current crossing each one of the power transistors
colector to emitter junction into stand by mode, with the input
shorted, so, no signal entering the amplifier circuit…. maximum
tollerable current to each transistor is 5 miliamperes each one.

Positive rail stand by current..having base shorted to ground, so,
no signal driving the amplifier…iddle mode, will be 37mA..and
this is measured using supply series protective resistance, that
resistance value is 10 ohms (10 watts minimum) and the voltage
measured directly into the extreme terminals will be 370 milivolts…
and this happens, only, when the power transistor emitter currents
are fine..or … measuring less than 2 miliampere to each power
transistors..and when they are 5 units…having more transistors, then
the current into stand by mode will increase depending the number of
transistors used.

Negative rail stand by current, having base shorted to ground, so, no
signal driving the amplifier… iddle mode, will be 29.4 mA…and this
must obbey all conditions written above….. this means 294 milivolts
measured over 10 ohms protective resistance.

regards,

Carlos
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Old 10th October 2009, 03:01 PM   #45
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Default Some currents and more details

Long tail current is 1.42 mA, so, half of that to each transistor into the differential pair

Bootstrapp/VAS current is 9.68mA

Driver current is 4.86mA

External VBE multiplier has 1800 ohms resistance from base to colector and a series of resistances from base to emitter....the first resistance is a fixed resistance of 750 ohms (or other you choice) and the variable one (trimpot) is adjusted into 150 ohms (can be a 220 ohms trimpot)...so..total resistance from base to emitter is 900 ohms... set this way during start up.

regards,

Carlos
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Old 10th October 2009, 04:47 PM   #46
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Default Post 44 had errors, reason why i am posting once again with corrections

Continuing with the specifications and details

The off set (Dc milivolts present into the output terminals due to
unmatching of transistor devices) is adjustable tweaking the 10k
trimpot, pré adjusted to 7200 ohms (R23)..of set will be around
1.0 milivolts

Current crossing each power transistor is measured monitoring
voltage Dc, milivolts range, directly picking the voltage into the
emitter resistances extreme leads (0.33 ohm)… the voltage
to be measure may be 750 microvolts..and this results into 2.2
miliampere of current crossing each one of the power transistors
colector to emitter junction into stand by mode, with the input
shorted, so, no signal entering the amplifier circuit…. maximum
tollerable current to each transistor is 5 miliamperes each one.

Positive rail stand by current..having base shorted to ground, so,
no signal driving the amplifier…iddle mode, will be 37mA..and
this is measured using supply series protective resistance, that
resistance value is 10 ohms (10 watts minimum) and the voltage
measured directly into the extreme terminals will be 370 milivolts…
and this happens, only, when the power transistor emitter currents
are fine..or … measuring less than 2 miliampere to each power
transistors..and when they are 5 units…having more transistors, then
the current into stand by mode will increase depending the number of
transistors used.

Negative rail stand by current, having base shorted to ground, so, no
signal driving the amplifier… iddle mode, will be 29.4 mA…and this
must obbey all conditions written above….. this means 294 milivolts
measured over 10 ohms protective resistance.

Differences in measurement around 20 percent plus and 20 percent
Minus are considered normal..do not worry with that.
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Old 10th October 2009, 04:48 PM   #47
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Default Post 45 had errors too... reason why i am posting it once again with some different

numbers..sorry folks..my mistake.
Some currents and more details
________________________________________
Long tail current is 1.42 mA, so, half of that to each transistor into the differential pair

Bootstrapp/VAS current is 9.68mA

Driver current is 4.86mA

External VBE multiplier has 1800 ohms resistance from base to colector and a series of resistances from base to emitter....the first resistance is a fixed resistance of 1000 ohms (or other you choice) and the variable one (trimpot) is adjusted into 260 ohms (can be a 500 ohms trimpot)...so..total resistance from base to emitter is 1260 ohms... set this way during start up.

regards,

Carlos
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Old 10th October 2009, 04:50 PM   #48
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Default Schematic, revision number one.

attached,

regards,

Carlos
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File Type: jpg Schematic revised one.jpg (767.9 KB, 186 views)
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Old 10th October 2009, 04:52 PM   #49
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Default Parts that does not exist into the Dx Amplifier standard pcboard

The one you can find at Greg Erskine home pages:

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

image attached.

regards,

Carlos
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File Type: jpg Parts not existent into the standard pcboard.jpg (720.0 KB, 160 views)
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Old 10th October 2009, 04:54 PM   #50
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Default Components that had their values changed

image attached,

regards,

Carlos
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File Type: jpg Parts with different values.jpg (739.3 KB, 147 views)
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