M 250 Dont wanna Work

[Reactance]

Weekend just passed and its Monday and what a blue monday it is.

Over the weekend i got all the components for building the M 250 amplifier, im not using a PCB just a simple veroboard.


Well after assembling the amp and taking and double checking my work, i turned it on, i used a +/- 30V supply and 100R in series with the supply just to be on the safe side.

The problem :

Well the green led turned on which indidates the voltage regulator is working, but wait a sec "T2" BC 556B is getting HOT !!! I checked the output and found 5Vdc on the output of the amp i turned the amp off and double checked my work again, i eveN replaced T2 still nothing the same result :-(. I did this with the 100R resistors in place of the main supply operating at +/- 30V.

Can someone please help me ?
Thanks in advance.

[janneman]

Originally posted by Reactance
Weekend just passed and its Monday and what a blue monday it is.

Over the weekend i got all the components for building the M 250 amplifier, im not using a PCB just a simple veroboard.


Well after assembling the amp and taking and double checking my work, i turned it on, i used a +/- 30V supply and 100R in series with the supply just to be on the safe side.

The problem :

Well the green led turned on which indidates the voltage regulator is working, but wait a sec "T2" BC 556B is getting HOT !!! I checked the output and found 5Vdc on the output of the amp i turned the amp off and double checked my work again, i eveN replaced T2 still nothing the same result :-(. I did this with the 100R resistors in place of the main supply operating at +/- 30V.

Can someone please help me ?
Thanks in advance.

What's an M-250? Schema?

Jan Didden

[jacco vermeulen]

Originally posted by Reactance
"T2" BC 556B is getting HOT !!! I checked the output and found 5Vdc on the output of the amp

There's DC current in the NFB line.
Means you did something wrong with the diodes or the DC-blocking electrolytic.
What kind of electrolytic capacitor in the feedback line did you use ?

[peranders]

Originally posted by janneman


What's an M-250? Schema?

Jan Didden

.... this:
http://www.atjoo.hostiz.com/m250.html

[lineup]

Originally posted by Reactance

Over the weekend i got all the components for building the M 250 amplifier, im not using a PCB just a simple veroboard.
------------
Can someone please help me ?
Thanks in advance.

Originally posted by janneman

What's an M-250? Schema?

Jan Didden

This is a big power amp ( ~250 watt )
that has been discussed several times before at www.diyadio.com
http://www.diyaudio.com/forums/search.php: M250


M is for Marcus - the name of constructor
He was posting a bit as member called:
marcus66 http://www.diyaudio.com/forums/membe...fo&userid=3004

For example about his M250 amplifier in this topic:
I have updated the M250 amp design (as well as my prototype). Please re-visit the URL posted at the top of this thread for the
new schematic. Thanks again to Djk, whose
comments have now been put to use.

Best Wishes,

Marcus


Article with schematics + some informations for build
published at his homepage:
M250 - A 250W stereo power amplifier



lineup audio informations

[lineup]

Here you can have a look and try to see what happens
at the schematic.
Uses parallelled MJ15024 / MJ150025 output!
http://www.atjoo.hostiz.com/schm250.jpg



Here you can have a look and try to see what happens
at the schematic.
Uses parallelled MJ15024 / MJ150025 output!
http://www.atjoo.hostiz.com/schm250.jpg

[janneman]

Originally posted by peranders

.... this:
http://www.atjoo.hostiz.com/m250.html

I see. Pretty standard stuff. I agree with Jacco's diagnosis, as far as you can tell without any measurements done.

BTW That C2 is way to large (or the series R way to small). Any output Z in the driving source or preamp and you lose your top end.

Jan Didden

[Reactance]

???

[darkfenriz]

Originally posted by Reactance
???

Use PCB.

[janneman]

A quick 'inventory' can be taken by measuring the voltages (DC, against gnd) on the terminals of T1, 2, 5 (no signal, shorted input). That would help us forward.

Jan Didden