Another amp

[ravslanka]

hi quasi

without your permission i modified your nmos200 pcb to suit my needs
i will be using this pcb for nmos350 please comment on this pcb
and also please suggest a matchiing pre amplifier based on opamps

i have already made nmos200
thanks for the lovely amp



with best regards

[ravslanka]

sorry ii posted in wrong thrread

[lineup]

Originally posted by chemelec
If anyone is interested, I have PCB's for this amp.
This One:

thanks, chemelec
very good

How do you design and produce your PCB boards layouts?
You use what software?

please tell me
Lineup

[lineup]

Originally posted by Workhorse

Ampman States That the M250 amplifier is unreliable amp due to folowing reasons:

1 The input differential is single ended.
2 Shared constant current source.
3 Complementary output stage.
4 Very low current gain of emitter follower stages.

Therfore due to above stated commentations M250 cannot be stated as reliable amp Acc to Professional Standards.


Regards
Ampman

That is your opinion, Workhorse.
I know you make great N-Channel HEXFET amplifiers in India.
I love your works, man

But you are not the only one to make good useful amplifiers.
We can do good DIY Audio amplifiers in Sweden, too.
Don't you think we can?
If not you think, then just build it and listen .....and you see


Regards
Lineup

[chemelec]

Lineup.......... I use an older program called: Quickroute , to create the artwork.
I produce the boards using a photograpic process.

Gary

[lineup]

Okay
thanks

[canca87]

hi all... i built this amp about 9 months ago, and it worked great... untill 3 days ago...

The symptoms, amost halved output power, and some audiable distortion at all frequencies. Ive put the amp through some frequency tests with a cro and signal generator and i can only see some cross over distortion on the output. I cant blame all this distortion im hearing on that can I? i mean it only just started happening, which makes me think ive cooked a transistor somewhere.

anyway, the reason im posting this problem here is because i cant see how a little bit of crossover distortion is making that much difference to what I hear, and also i wouldnt know where to start in removing it.

anyway, im new to this forum (well im an avid reader) so be nice :P.....

[chemelec]

As a Simple Test:
With the amp on, But No Input signal, Check the Emitter to Base Voltages on All Transistors. It should be About 0.6 Volts.

If Not, the transistor is probably bad.

This MAY help you find it easily.
HOPEFULLY!

Gary

[canca87]

ok, i measured all the Vbe values of all the transistors. Here are the results:

T1-0.6v, T2-0.6v, T3-0.57v, T4-0.6v, T5-0.6v, T6-1.02v, T7- 0.51v, T8-0.54v, T9-0.56v, T10 to T13-0.26v, T14 to T17-0.54v, T18-0.64v

well for some reason the Vbe of T6 is rather high, unsure as to why as that is the shortcircuit protection. Wonder whether that means i have a short someone on the output tracks, will check that later..

As for the main output transistors T10 to T13, seems a bit low. That might explain crossover distortion. But what does this mean? output transistors faulty? something else causing them to become unbiased?

any ideas? still at a loss...

[chemelec]

I would definately Suspect problems with T10 to T13.

Since they are in Parallel, It may be only One of these causing the Problem.

And that 1.02 Volts on T6 also seems STRANGE.

You could Remove T10 to T13 and put in Just One New Transistor.
Than test the Base to Emitter voltage of it and see if the voltage is Corrected.

Without knowing your Electronic capabilities, Its hard for me to advise you on trying to test the origional T10 to T13 transistors.