Re: Need Help Troubleshooting UBit-X #ubitx-help

Bill Cromwell <wrcromwell@...>

I do not have a momentary short on my audio jack as the ring (the middle connector is not wired to anything. I do not expect to ever listen to stereo on the frequencies this covers and so I just left it unused. I did not install aitcraft landing lights on my van, either <evil grin>.

Meanwhile I have long been in the habit of not plugging-unplugging my radio gear while it is powered. Even some legacy gear balks at that. I have the V3 uBitx with the non-WX chip and everything is happy.


Bill KU8H

On 1/23/19 11:16 AM, Jerry Gaffke via Groups.Io wrote:
OK, thanks to Raj for clarifying this.
I remember him reporting the non-WX TDA2822 could get remarkably hot
when driving a low impedance speaker with lots of audio,
did not recall it blowing.
Several solutions for this, any should work on non-WX TDA2822's:
  Put your finger on the TDA2822 when trying high volume levels, back off if it gets uncomfortably hot (over 60C).
  Add a resistor of 10 or 20 ohms in series with your low impedance (4 ohm?) speaker.
  Add a voltage regulator to supply less than 12v to the TDA2822
When the TDA2822's first started blowing, we were all scratching our heads as to why.
Were several reports of having it blow the moment headphones or speaker got plugged into the rig
Eventually we figured out that the parts that were blowing were marked "WX" not "FCI",
and that the momentary short put them over the edge.   In many cases the "WX" parts
blew spontaneously and not at high volume, these clones simply can't deal with 12v.
There are web reports of other TDA2822 clones that fail miserably at anything much over 6v.
The original TDA2822 from ST (and NJR's NJM2073D) is rated for an absolute max voltage of 15v,
a max working voltage of 12v, though being a linear class AB amp will dissipate as much power in heat
as it gives in audio to the speaker.  Operating at 12v, it is possible to exceed the max
dissipation rating if you crank up the volume, and the chip will slowly heat up.
A momentary short at the headphone jack should not blow a quality TDA2822,
it would take time for the heat to build up enough to destroy it.
Though to be safe, not a bad idea to avoid shorts.
I have an FCI marked TDA2822 on my v3 uBitx, I have not bothered with any fixes.
Though I'm not trying to fill the house with the music of shortwave radio,
as not everyone here finds it quite so musical.
Jerry, KE7ER
On Tue, Jan 22, 2019 at 09:54 PM, Raj vu2zap wrote:
I have had some non-WX chips fail at loud levels. On Tue, Jan 22, 2019 at 10:19 PM, MVS Sarma wrote:
The TDA2822 should not have failed but for two reasons explained by
many. I am just recapitulating them.
1. Stereo out jack with mono earphone or external speaker plugged.
This situation created short at the amplifier output.
2. using the device at its extreme working voltage. See anywhere,
you find that this device is used only at 3 or  6V.
 Solutions where implemented , the devices should be working even now.
bark less - wag more

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