TDA2822

Maybe Claude is your Santa:
? ??/g/BITX20/message/43156
The uBitx needs the extra gain of a 1uF cap between pins 1 and 8 as on the Bitx40.
(The 0.1uF cap of post 43189 is likely not adequate.)

So yes, the audio power amp is fairly easy to build a daughterboard for.
The band switching relays provide plenty of holes for mounting a daughterboard there if somebody wants to mess with the LPF's.
The two TR switching relays likewise provide nice holes for a solid state TR switch solution.
The transformers provide handy holes to mount daughterboards to replace the diode ring mixers and parts of the transmit PA.
The bidi amps are probably fine as they are, seem to work well.? If you want a different amp, put it on a mixer daughterboard.
I'd like to see additional holes for mounting daughterboards over the other filters, the 30mhz LPF, the 45mhz, and the 12mhz.
Maybe some thought of making it easier to substitute audio preamps for mike and rx, also the modulator on the next rev board?

But really, 1206 pads are big enough to hack wires to.
The uBitx is almost modular enough as it is for my purposes.

Jerry, KE7ER

Thanks Satish, John and Arv.

I did not have the BPF connected at the time of experimenting. But it would probably lower the signal even more. So it's best to get a strong signal before I attempt modifying the BPF. Satish makes a very good point, there is a 0.2 V loss in the 1N4841 diodes of course. Why did I not think of that myself? I did pass the exam but it's been a while. ;)

I will try John's suggestion and crank up the signal a bit to around 0.6Vp-p. Will post here how it turned out.

Arv, I use small pieces of (leftover) copper clad board, about 2.5 x 4 cm in size, around 1 by 2 inch per module and simply solder the components on dead bug style. I cut some small squares and glue them on as solder-islands where needed. The modular approach is great because you can test them individually. When I get to the final I will need a slightly bigger board and when everything is finished I will put all small prints on a larger board. Maybe put some 12V, TX and RX rails on it and I will call it the motherboard as well.

Well... my UbitX came Mar 5/18.. Was ordered Dec 20/17.. Serial # is
728/02 . Raduino serial # is 805/2 . I am putting it in a Banggood
case. I am also going to use a larger heat sink on 510's and put a
current limiter on the PA power line. That might help. The 8222 IC is
FCI one so should be safe. I am very impressed with the package and
the plastic box. Now the fun begins ! Graham
VE3WGW

Solution 3: 78L09. the center lead looks soldered but it is floating
but the tab is soldered to the copper below it. The white wire is my
fix for prevent the filter relays from clicking during PTT. Yes the
board needs a brush cleaning!

The audio is fine but distorts at high volume. The 9V voltage out
does not drop at max volume.

Emacs!




At 06-03-18, you wrote:

I did some experiments with the chip failure.

FCI chips were sourced locally and plugged in. No failure with
normal volume. I raised the volume to a high level and the chip
failed immediately!

Solutions

1: Add a resistor in series with the 12V line maybe 10-15 ohms to
drop the voltage.

2. Simple solution is to use only a 16 Ohm speaker or add a series
8-10 Ohm resistor with the 8 ohm speakers.

3. Cut the power track to the TDA and insert a 78L08 or 9 to reduce
the voltage. There is a track which can be cut
and a SMD or leaded regulator can be soldered on the board. This
track leads directly to the chip and filter cap.

The second solution may be the simplest.

Further experimentation scheduled for tomorrow!

开云体育

Well it is time to get off the Pot and ship the first of the new Ubit RaduinoUMax.

Working like a beaver here since the PCBs arrived Friday!

The MAX is for the 16 Added I/O pins on the end of the PCB.?? It makes the PCB a little longer, but still fits into uBit Radio PCB.

I2C control gives you 16 more 5V digital In or Outs.

Uses Adafruits Library for simple control of them.? 3 I2C address jumpers to make sure you can use other I2C items.

73's

Mike, WA6ISP

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10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
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