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newbie questions about transistors and power suplies
newbie questions about transistors and power suplies
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Old 7th September 2002, 05:56 AM   #11
Jared is offline Jared
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i have the parts list and the schematic within a 4 page build guide. I dont have a working scanner on theis PC, and it is 2 am, so it will have to wait til tomorow. I will get those scans, pics of the assembled mess, and the results of the transistor test you suggested here tomorow afternoon.
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Old 7th September 2002, 06:44 AM   #12
skaara is offline skaara  Slovenia
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q1: Toroids weight less, they have lower losses, the are shaller than EI ones and they dont create so much magnetic field around themselves.
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Old 7th September 2002, 12:06 PM   #13
trwh is offline trwh  United Kingdom
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Hi Jared

There is a brief description of a DIYer's experiences with the amp here:

http://www.soton.ac.uk/~apm3/diyaudio/Maplin_150W.html
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Old 7th September 2002, 01:38 PM   #14
Jared is offline Jared
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Default here is the scan of the pamplet

www4.ncsu.edu/~jdchmiel/amp.zip


Transistors have direct short from any terminal to any other terminal. This is in circuit (okay or need to measure out of circuit?)

If all I do is buy the MJ15003/MJ15004 pairs to replace the 2N3055/MJ2955 pairs it should work as good or better than original? (assuming it is transistors that are only thing bad?)
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Old 7th September 2002, 02:11 PM   #15
Jared is offline Jared
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interesting... when searching for datasheets on the MJ15003 i found a web page about conterfeit parts... well the pic http://sound.westhost.com/fakes-r1.jpg has a 2n3055 in it, and the 2n3055 that came in my maplin kit bought from qkits.com has an almost white top, with black lettering, oriented the same way, but with an ST logo, and the print is almost gone !! I think it is a fake.. I am gong to open it up since it is dead anyways.
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Old 7th September 2002, 02:52 PM   #16
Aud_Mot is offline Aud_Mot
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To start:

If you have to ask the question, you don't have enough expertise to try it.

ALWAYS USE A TRANSFORMER!

The risk of electrocution and fire is too great.

Transformers are your friends.

I do not know that a toroid tarnsformer is automatically better. You can point to some specs and support the argument. Like many things in engineering/design it is a series of choices and trade-offs. Toroids are popular and do have thier advantages.

In a power amp, I use them. However, there have been plenty of well regarded commercial power amps (from well regarded engineeers) that used EI transformers.

In pre-amps and lower level ciruits, EI laminates have thier advantages.

The transistor answer depends on which amplifier class you are running the output stage. Class A, your 5% - 95% concept is nominally correct. In Class AB (some texts call it this Call B) you do not have this "extra wasted power."

The "extra wasted power" gets disapated in the form of heat. Class A amps need large heatsinks. Class AB run cooler and do not need as large heatsinks.

My above explaination is simplified. It is more complex than I have stated above. It will help you make the big decision about what kind of output stage you wish to impliment.

I would suggest 2 books:

High-Power Audio Amplifier Construction Manual
by G. Randy Slone, Randy Slone

Audio Power Amplifier Design Handbook
by Douglas Self

Reagrds,

Aud_Mot
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