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Old 10th February 2009, 02:09 PM   #1
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Default Bip350 amp. help!

about the bip350 nchan amp...

the required voltage was +70v 0 -70
i used 38-0-38 ac, 6ampere transformer, 1 bridge rectifier and 4pcs 4700uf/ 63volts electrolytic capacitors....

that power supply brought me around more or less 54volts
and i believe that cuirciut would work fine but would give me lesser output than 350watts,

instead of using 200 ohms trimmer resistor which was not available here in our place.... i used 100 ohm trimmer resistor for biasing. i adjust the offset voltage from ground to the output and i got 0.1volt and i adjust the 100 ohm bias resistor (originally 200 ohms in the image attached) and i got +0.5 and -0.5 respectively....

with that result i presumed that the amplifier i've made was fine. so i connect the output transistors and fed audio signal from the dvd player. all was fine except for the humming. and the power output at full power can be compared to a 40watt amplifier or even lesser....

here's the bip350 nchan
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Old 10th February 2009, 02:14 PM   #2
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i used a CROWN 8ohm 300watts instrumental speaker

Thanks,
riche
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Old 10th February 2009, 02:22 PM   #3
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i omitted the 10 ohm resistor in the input ground and directly connect the input ground to the main ground of the circuit... the 50% of the humming was illiminated... but the humming was still there... and can be heard at low volume. but the power did not change... theres no enough power to drive my 15" 8ohms 300watts speaker.

riche
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Old 10th February 2009, 04:25 PM   #4
AndrewT is offline AndrewT  Scotland
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Hi,
measure the voltages across C7, R20 & R22 with VR2 (100r instead of 200r) set to minimum and to maximum.

Measure the voltages across the 7 emitter resistors in the front end.

Measure the voltage across R23 & R27.

Measure the output offset.

BTW.
that +-70Vdc is the maximum. There is nothing wrong with using +-54Vdc. Expect about 250W into 4r0.
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regards Andrew T.
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Old 11th February 2009, 12:52 AM   #5
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hi richie
greetings check c8 100 uf 63 volts is it connected correctly
negative of condenser going to 1 k resistor but layout shows positive

thanking you
andrew lebon
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Old 11th February 2009, 07:01 AM   #6
quasi is offline quasi  Australia
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A good point to start would be to check your physical wiring with attention paid to the grounding and earthing. In my amp projects I run a connection from the central ground (0v) to a chassis earth.

Then check voltages as AndrewT has suggested. If you like report what you find and we might be able to help.

If all checks ok, try and get access to a CRO and look at the output waveform to see if you can get it to clip. This will tell you if the amp will swing rail to rail. A previous constructor of a similar amp put the wrong resistor in the feedback network and gave his amp a gain of about 3 instead of 33.

Finally eliminate an earth loop problem by connecting the DVD chassis to the chassis of the power amp.

This amp should run absolutely quiet and quite well with rails of +/- 54 volts DC.

Cheers
Quasi
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Old 16th February 2009, 07:22 AM   #7
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hi guys...

i cheched the parts, all are ok and in the right place..

i measured ground to the output without the output transistors...
and ive got a +0.05volts

and at the base to imitter of the output transistors:
_+ and - 0.6volts. it ranges from 0.4volts to 0.8volts each rail...

i run a wire from ground 0 to the chasis and around 5%... humming still present..but when i tested the amp at mid volume after 5hrs one channel is dead. 1 driver, 2 - 39ohm 1watt, were all burned, 1 - 1n4148 beside the 33nf capacitor and 8 - 0utput transistor is shorted .

by the way i use an EI core transformer... will it affect?

i accidentally drop my digital cam so i cant show the picture...


thanx
riche
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