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U1 fried

Tom, wb6b
 

I concur with the resistor suggestion. Here is how I wired my speaker jack.

The lowest value resistors I had was 15 ohms, so I used that. Going lower may be better. Also, I used two resistors so if a monaural plug is plugged into the jack it will not short out the sound.



Tom, wb6b

Dennis Yancey
 

One of the things that might help is to install a resistor on the jack that comes int play when you remove the speaker plug. This could be anything from 6 - 30 ohms as the Impedence of the TDA is Bout 32 ohms. If you installing it at the pin that makes contact with the tip when the plug is removed and connect it to GND, this would assure a load on the output at all times. I would recommend a value around 8 - 16 ohms as that is two of the most common impedences in speakers, The other is 4 ohms and I would stay away from this value as the current is going to go way up on the 2822.  Good luck. 
--
72 and God bless
KD4EPG

Howard Fidel
 


I used an LM380.

Howard

On 4/29/2018 7:19 PM, Kd4epg@... wrote:
Love to see some pics of this adapter. Also, did you look at the NE5532? May be an easier one to make.
--
72 and God bless
KD4EPG


Dennis Yancey
 

Love to see some pics of this adapter. Also, did you look at the NE5532? May be an easier one to make.
--
72 and God bless
KD4EPG

Jerry Gaffke
 

I like the little wheelchair they use for a logo.

John
 

This are the TDA2822Ms I received from China ordered on eBay

Jerry Gaffke
 

On the other hand, a resistor in there limiting voice peaks 
might be useful as a simple form of AGC.
A loud signal coming in will distort, but probably won't make you go deaf.


On Sat, Mar 3, 2018 at 03:33 pm, Jerry Gaffke wrote:
Resistor R111 is in the Bitx40 to form a low pass filter along with C110 to reduce power supply noise in the audio.
It is not there to reduce the supply voltage into the LM386 (though limiting current might be a useful safety net there). 
Raj found 100 ohms distorted the audio, he reduced that resistor to 10 ohms:
    https://groups.io/g/BITX20/message/34520

Jerry Gaffke
 

Maybe not a good idea to just add a dropping resistor to the TDA2822 supply.

Quiescent current with no incoming signal on the TDA2822 is around 9ma,
and increases to nearly 1 Amp on audio peaks (I have not measured this, just looking at the datasheet).
So power supply into the TDA2822 will be anything between 11v and 0v if you add that 100 ohms,
depending on the audio level.  If some of the clone TDA2822's blow at 12v, it is quite possibly just 
the voltage that is doing that, even if the chip is only drawing the quiescent 9ma.
If you want to reduce the supply voltage to the TDA2822 properly you will need a regulator, not a resistor.

Resistor R111 is in the Bitx40 to form a low pass filter along with C110 to reduce power supply noise in the audio.
It is not there to reduce the supply voltage into the LM386 (though limiting current might be a useful safety net there). 
Raj found 100 ohms distorted the audio, he reduced that resistor to 10 ohms:
    https://groups.io/g/BITX20/message/34520

Jerry


On Sat, Mar 3, 2018 at 02:31 pm, <Mharpen@...> wrote:

Hello. The LM386 audio chip in the BITX40 is powered via the RX rail thru a 100 OHM resistor

R111. Under normal operation (in my shack 12 V gelcell) this resistor drops about 4 volts with moderate audio. Thus, the chip is powered by about by about 8V. This of course would fluctuate with audio lever if not for the 470 uF capacitor (C110) which should smooth out small fluctuations.

 

The DTA2822 in the uBITX is powered directly via the 12 V power line without the dropping and smoothing RC circuit. Thus, it would see the full 12 or (13.8) volts. This is done, presumably, to facilitated CW (reduce CHIRPing). This is probably why the less robust DTA2822s fail. I'm not particularly interested in CW so when I finally get my uBITX I will replace the the WX with an ST chip and install the same RC circuit as in the BITX40.

 

Mike N6CMY

Mharpen@...
 

Hello. The LM386 audio chip in the BITX40 is powered via the RX rail thru a 100 OHM resistor

R111. Under normal operation (in my shack 12 V gelcell) this resistor drops about 4 volts with moderate audio. Thus, the chip is powered by about by about 8V. This of course would fluctuate with audio lever if not for the 470 uF capacitor (C110) which should smooth out small fluctuations.

 

The DTA2822 in the uBITX is powered directly via the 12 V power line without the dropping and smoothing RC circuit. Thus, it would see the full 12 or (13.8) volts. This is done, presumably, to facilitated CW (reduce CHIRPing). This is probably why the less robust DTA2822s fail. I'm not particularly interested in CW so when I finally get my uBITX I will replace the the WX with an ST chip and install the same RC circuit as in the BITX40.

 

Mike N6CMY

Jerry Gaffke
 

Pavel,

All the reports on blown TDA2822's thus far in this form had a logo of "WX" on them.
Can you describe the markings on your chips?

Thanks for the report!
Jerry


On Fri, Mar 2, 2018 at 10:22 am, Pavel Milanes Costa wrote:

I was some time in the past in almost daily touch with the infamous TDA2822D/M as per my experience they do not like to go beyond 8V or you get it to much heat and one of the channels will fail or you will have it's brains all over the place... like you are seeing here (no plugging/unplugging in my application)

The circuits I fixed had 100uF on the outputs, so I doubt that lowering the 470uF output filter do much to mitigate this.

In vote to point that this IC are clones of lower quality and does not like to go over 8V or they to strange things like this.

Cheers Pavel CO7WT.

Pavel Milanes Costa <pavelmc@...>
 

Jerry et all.

I was some time in the past in almost daily touch with the infamous TDA2822D/M as per my experience they do not like to go beyond 8V or you get it to much heat and one of the channels will fail or you will have it's brains all over the place... like you are seeing here (no plugging/unplugging in my application)

The circuits I fixed had 100uF on the outputs, so I doubt that lowering the 470uF output filter do much to mitigate this.

In vote to point that this IC are clones of lower quality and does not like to go over 8V or they to strange things like this.

Cheers Pavel CO7WT.


El 02/03/18 a las 11:18, Jerry Gaffke via Groups.Io escribió:
There's a photo at the end of that webpage where I can just barely read a "CX" logo on their problematic TDA2822.
So WX and CX are perhaps best avoided?
I have no idea who "CX" is, though possible what I am seeing is a clone of a Sony part number? (google Sony CX767)

Perhaps Steve could tell us more about how those parts are marked.

Jerry, KE7ER


On Thu, Mar 1, 2018 at 02:23 pm, G1KQH wrote:
Recently I found some TDA2822's on ebay from China, I got the GQRP club to purchase a batch ( I bought 50 too ). Tony Fishpool (G4WIF) setup up a test and found although they worked well at low Volts they got hot over 7V!:
His findings are made public here on his website here: http://www.fishpool.org.uk/audioamp.htm
Food for thought!
73 Steve
GQRP 11049
http://g1kqh.blogspot.co.uk/

Jerry Gaffke
 

There's a photo at the end of that webpage where I can just barely read a "CX" logo on their problematic TDA2822.
So WX and CX are perhaps best avoided?
I have no idea who "CX" is, though possible what I am seeing is a clone of a Sony part number? (google Sony CX767)

Perhaps Steve could tell us more about how those parts are marked.

Jerry, KE7ER


On Thu, Mar 1, 2018 at 02:23 pm, G1KQH wrote:
Recently I found some TDA2822's on ebay from China, I got the GQRP club to purchase a batch ( I bought 50 too ). Tony Fishpool (G4WIF) setup up a test and found although they worked well at low Volts they got hot over 7V!:
His findings are made public here on his website here: http://www.fishpool.org.uk/audioamp.htm
Food for thought!
73 Steve
GQRP 11049
http://g1kqh.blogspot.co.uk/

_Dave_ K0MBT
 

I wired my jack to plug in a monaural speaker as the case I used was small. Soldered the leads to the middle and tip. That way when I wanted to plug in stereo headphones both sides will work.

G1KQH
 

Recently I found some TDA2822's on ebay from China, I got the GQRP club to purchase a batch ( I bought 50 too ). Tony Fishpool (G4WIF) setup up a test and found although they worked well at low Volts they got hot over 7V!:


His findings are made public here on his website here: http://www.fishpool.org.uk/audioamp.htm


Food for thought!

73 Steve

GQRP 11049

http://g1kqh.blogspot.co.uk/

Mike Woods
 

On 2/03/18 10:00 AM, Mvs Sarma wrote:
Whether it could be batch wise observation?
 I don't remember such cases reported earlier

I do say in the article:

"However, it could equally as well be a run of bad chips, or the fact that the device is running near its voltage maximum (it is rated for 15v maximum)."

I suspect you are correct Sarma in that this could be a batch issue with the TDA2822, in the same manner, there seems to be occassional runs of postings about K3 or K1 relay failures.  Yet most of us don't have problems with component failures.  Just user error!

Mike


--
Mike Woods
mhwoods@...

MVS Sarma
 

Whether it could be batch wise observation?
 I don't remember such cases reported earlier


On 2 Mar 2018 02:25, "Mike Woods" <mhwoods@...> wrote:
Hi everybody

I have tried to summarise what we know about the TDA2822 problem, prevention and fixes in this article on ubitx.net:

http://ubitx.net/2018/03/01/tda2822-problems/

Let me know if you can suggest further improvements to my text.  We don't want 2000 µBITx owners to go through the same pain as some of you have experienced ...  I hope to insert a resistor in the output circuit today!

73 Mike ZL1AXG


On 2/03/18 9:50 AM, Claude-Alain Baumgartner via Groups.Io wrote:
Hi Howard,

Yes, both pins 2 and 4 of the LM386 go to pin 4 of the socket (ground).

Regards,
Claude


--
Mike Woods
mhwoods@...

Mike Woods
 

Hi everybody

I have tried to summarise what we know about the TDA2822 problem, prevention and fixes in this article on ubitx.net:

http://ubitx.net/2018/03/01/tda2822-problems/

Let me know if you can suggest further improvements to my text.  We don't want 2000 µBITx owners to go through the same pain as some of you have experienced ...  I hope to insert a resistor in the output circuit today!

73 Mike ZL1AXG


On 2/03/18 9:50 AM, Claude-Alain Baumgartner via Groups.Io wrote:
Hi Howard,

Yes, both pins 2 and 4 of the LM386 go to pin 4 of the socket (ground).

Regards,
Claude


--
Mike Woods
mhwoods@...

Claude-Alain Baumgartner
 

Hi Howard,

Yes, both pins 2 and 4 of the LM386 go to pin 4 of the socket (ground).

Regards,
Claude

K4LXY
 

Thanks, Jerry.  I have an adapter made and will give it a try.
Howard 

Jerry Gaffke
 

Yes, 2 wires to TDA pin 4.

TDA pin 4 is ground on the uBitx.
LM386 pins 2 and 4 are both ground on the Bitx40, and thus both must be wired to TDA pin 4.

Claude has left pins 1 and 8 of the LM386 unattached, the LM386 datasheet states that
in this configuration it has a voltage gain of 20, or 20*log10(20) = 26dB.
The LM386 on the Bitx40 has a 0.1uF cap between pins 1 and 8 to increase the gain to 46dB.
The original TDA2822 of the uBitx has a gain of 40dB, so you may want to try adding a cap between LM386 pins 1 and 8
if you need more gain there.  A larger value cap (up to 10uF) would improve low frequency response.



On Thu, Mar 1, 2018 at 10:20 am, DrZ wrote:
I note you have 2 to 4, and 4 to 4.  Are there two wires going to the TDA pin 4?