King Cobra PCB

[mayky]

Of course

[kt315]

And a picture, my PCB

can you upload bottom PCB side pic?

[mayky]

THANKS

[kt315]

I changed the transistor, but the noise is now, just louder

you can block the noise like i did. i gave this mod many times. but that is FOR ROOM.
for field you have to be back a schematic to original.

[kt315]

a noise goes throught out U9-B Q8 U15 Q10 Q11 speaker. what new you open for me? I had (HAD) answered
on this matter lots times before but you do not wish read this forum. and again again again ask me why there is noise.
do you guess to hunt INSIDE YOUR ROOM OR WHAT??? or AT FIELD?
so WHY you ask me about 50Hz electric influence inside your room? if you broke your walls and roof
you discovery HUGE AMOUNT METALIC ARMATURE inside the concrete. so why you ask me why
the influence does not give you the repose? leave this matter and go into wood.

[mayky]

Notch filter is off.

[kt315]

I changed the transistor, but the noise is now, just louder

do not use NOTCH filter connected. YOU ARE ABLE READ WHAT I WRITE?

[mayky]

I changed the transistor, but the noise is now, just louder

[kt315]

yes, certainly, those are ordinary transitors, nothing so specific. BC..... and 2N.... PN... are clear US type manufacturing tr-s
and you must know more about than me in Lithuania. Lietuva is so tiny state you are not able to find it at a map
while US is HUGE and cover ALL CONTINENT. Lietuva is some kinda a point from your pen at paper you touch.

look W. Lahr schematic with ORIGINAL tr-s.

[mayky]

I found a mistake. The 2N2222 to not use the same pinout p2n2222a. I Use p2n2222a, and fault.
What is transistor using the original Cobra? Can I use any BC..... transistors. I have yet.

[mayky]

What freqvency u15 (PowerSupply) pin2 ? 560 Hz ?

[mayky]

Some scope pictures: disc mode
1. U9 pin 1
2. U9 pin 7
3. Q11 base
4. Q10 base

And a picture, my PCB

[mayky]

Thanks for answer.
Here is the noise

[kt315]

the IC9 1 and 7 pins here is 50 Hz square vawe --- yes, in conditions of your room with whole electrci lines around
you will see 50Hz. and what? this noise does not go via U14-A just cause U13A&B are turn out. follow the logic work
of the schematic.
The negativ power is only -6 V insted -8 V. -- do not know this is bad or good. must work. I measured and suggested
to measure the negative voltage BEFORE while soldering. D10 - then use Zener diode.

[mayky]

Hi
I made a cobra pcb, double sided but not hole platted. I solder components top and bottom. But not work correclty when i swith disc mode some noise come out. If i all switch off the IC9 1 and 7 pins here is 50 Hz square vawe. The negativ power is only -6 V insted -8 V. Some idea what is the problem ?