MAT02, 03 Elektor preamp schematic

[arasuk]

Hi



(I Just build the circuit & tested this preamp, finding its quality Appreciation in this Thread.
I am having some problems, This preamp is giving out DC ?ve10.23 volts, I have checked no shorts, I have Used Bc 550/560c Instead of MAT 02/03, due to the non availability of original matched transistors.)

Hope guys here will help me.

Thanks
Arasuk

[ashok]

Hi Arasu,
Double check the connections on the input transistors . B,C,E are connected right ? You obviously have a dc problem. Chances are that you either have some part wrongly connected or have some track error ( where did you get the pcb ). Sometimes errors look fine even if you look at it 10 times. So take a big break and then look at it again.
Cheers.

[sivan_and]

arasuk wrote:

I have Used Bc 550/560c Instead of MAT 02/03

Probably mismatched i/p diff pair trans ..

[sivan_and]

I have a couple of dual transistors labled TD401, no data available so far...any help will be appreciated .THANKS!!

[arasuk]

Hi Ashok & siva,

Thanks for the reply, I checked the pcb again no shorts or any mistakes , still O/P of - 10.6 volts ,


The I/p Diff trans are not matched but then I should be able to get may be 100 Mv or 300 mv not -ve 10.6V


I had the same prob as mr samuel had I have mat 02 & mat03 ( PMI )But MAT 03 are NPN misprinted .

Ashok : I got the PCB done by Elektor Book after hunting for long long time for the back issue.I got it with LEGEND and Solder mask so no shorts shall happen.

Let me know if anybody faced the same prob and rectified .

Thanks

Arasuk

[sivan_and]

Try to force a DC voltage through a high value resistor eg:1Meg.
to one i/p direct ie to the base of i/p trans. Use a 100K preset and connect either end of preset to the supply rails and the wiper thru 1Meg said resister. And note any change in the output offset voltage..........If it changes..then u had to match the trans pairs...try it and let me know

[udip]

Anyone knows a good replacement for the BF256 and
the BC327-40/BC337-40 ??

It's hard to find them here in israel...

[Nexus]

Hello,

for the bf256 you can use bf245b or bf245c instead.

best regards.
Nexus

[r!sc!]

Can anyone post the PCB for this preamp.
Thanks.

Boban

[r!sc!]

Originally posted by resolution
Hi Nexus,

Sorry about the delay getting back to you.

As it happens I do. I use Pads PCB. I can email the file to you as is, or compile it into a multi-page pdf. It is a double layer with top ground plane.

I've included a 3 page pdf for your perusal.
P1. Schematic
P2. Top
P3. Bottom

All PCB layouts are 2:1 un-mirrored

If you need all the PCB details in pdf or CAM photo then can you give me a few of days - it my wife's birthday the day after tomorrow and things are just a bit manic right now with that and work.

Let me know what you require.

Kind regards

res

Hi,

can U send me PCB files to bobannesic@gmail.com or just use my email below.

Boban