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Mike Woods??ZL1AXG, has a comprehensive writeup of v3 TDA2822 issues here:
? ??/g/BITX20/message/82143
Along with other good stuff on the *BItx* rigs.

Speaking of whom, we haven't heard from Mike for nearly a year now.
He's in my thoughts.
? ??/g/BITX20/message/82143

Jerry, KE7ER

Bruce,
Glad we could help.? Always feel free to post to a new topic with any questions.? The more information you can provide the easier it is for us to help.? You can also post back to this topic as well.

Have fun!
73
Evan
AC9TU

The ones you ordered will probably work fine, but Ebay vendors can be a gamble.
The TDA2822M in the 8 pin DIP has been discontinued by the original manufacturer
? ?
It was a popular device, and perhaps a dozen different shops are now building clones of it.
The original device was spec'd for operation to 12v, an "absolute max" of 15v beyond which it might be destroyed.
Some clones lowered the "absolute max" on their datasheet to 12v.
And some of those clones, even if they have a datasheet claiming 12v max, would be destroyed if used beyond 8v or so.
Most clones don't have a datasheet.

If I were to buy a replacement part, I'd go with the JRC?NJM2073D as recommended by Raj,
and buy it from a reputable distributor who I know will not be substituting some clone.
Some Ebay sellers go so far as to scrape off the markings of a cheaper low frequency TO220 FET, mark it as a $0.50 IRF510.

Regarding the stock v3 uBitx, they all apparently went out with either FCI or WX branded TDA2822M's.
Very few of the FCI brand parts had troubles, though you could exceed power dissipation limits
if operating at 12v or more, with volume up to full blast, and/or driving into less than 8 ohms.
Some WX brand parts worked fine at 12v, others blew in a puff of smoke at some random moment.
When buying replacement TDA2822M's on the web, there are many other clones beyond FCI and WX that you might get,
some of them have similar issues to the WX, few have a datasheet, almost none claim an absolute max of 15v.

I am not aware of problems with any of the LM386 clones blowing at supply voltages of 12v,
though some have far more distortion than others
? ?
.
Possible fixes for those with the WX brand TDA2822M parts in their v3 uBitx:
? ? Replace with a?NJM2073D or similar known good clone
Hack in an LM386 following the schematic of the v5 or v6 uBitx, a matter of swapping pins around on that DIP-8 part..
? ? Use one of the many LM386 amplifier breakout boards available on the web, tie it into the volume pot wiper.
? ? Reduce the supply voltage into the WX TDA2822M to 6v (instead of the stock 12v) by adding a 3 terminal voltage regulator?
? ? Adding an 8 ohm resistor in series with the output of the TDA2822M is not a bad idea, but the primary issue is the supply voltage.

The TDA2822 was a fine choice for the v3, I was sad to see it dropped on the v4.
The issue was simply one of buying sub-standard parts.?
That can happen with most any electronic part if you are pressing for low cost.

Another v3 issue regarding substandard parts was the provided BNC connector,
some of them were machined out of spec such that the center pin did not make good contact.
The antenna connection was intermittent when the coax was wiggled, subjecting the finals to high SWR..
That does not mean BNC connectors should be avoided, it means you must choose a vendor that sells good parts.

A search for "TDA2822" in this forum will find some very long discussions about all of this when the uBitx came out.
There were a half dozen different theories as to why some failed, it took months to figure out that it was primarily
a problem of the WX brand parts failing when powered from more than around 8v.

Jerry, KE7ER

I think you nailed it on the DTR setting. I got a fresh load of flrig (via a PPA) and in the Configuration window clicked off DTR. I was then able to change the frequency, the mode, switch VFOs, etc. Now it's on to fldigi! Thanks for the help.

Bruce,

Like Doug, I do not use Linux or iOS with either of the fl programs you listed, so cannot comment on your specific error messages (though most of the time they are permission issues in Linux systems).? I have connected a v4 uBiTx to a Raspberry Pi running WSJT-X.? In your case, I would go back to the fldigi and flrig setup and verify that you are not trying to use DTR or RTS signals, as the uBiTx does not support those hardware signals.

Verify the settings in the digital interface programs to match what Doug displayed in his post.

Just a suggestion.
73
Evan
AC9TU

I did my order on Ebay,? are the chip on Aliexpress? the same?
I see 10 pieces plus shipping for 5 Euro ,have to wait? for delivery? sep. oktober
Thx in advance 73
ON3MK
Mor?

On Sun, Aug 15, 2021 at 05:01 AM, Tom, wb6b wrote:

(would that be similar to I/Q, allowing many types of modulation to be created?)

I've looked a bit more at the amp article. In this case, maybe not. But an interesting idea, nonetheless. Combining two power amps "in series" to combine (add) I and Q signals at the very final output stage.

Tom, wb6b

On Sun, Aug 15, 2021 at 03:05 AM, <quad@...> wrote:

Folks over on amfone have being trying out SIC and GaN designs and might be useful source for ideas?

The class E amplifier (at?) with "in phase, out of phase" drive (would that be similar to I/Q, allowing many types of modulation to be created?) looks interesting. This is still retro in a way because of the variable capacitors to "tune" the RF output network.?

The amfone examples are examples of high voltage returning to ham radio.

Tom, wb6b

Folks over on amfone have being trying out SIC and GaN designs and might be useful source for ideas?

http://www.classeradio.org/8_fet.htm


http://amfone.net/Amforum/index.php?topic=42504.0

An interesting HaD post by Ryan Flowers -

https://hackaday.com/2021/08/14/surplus-syringes-make-satisfactory-tuner-for-amateur-radio-experimentation/

Ordered? 5 pieces, thanks for helping me?
73,
ON3MK?
Mor

Looks like a good one Mor, buy a few extra.

Raj


At 15/08/2021, you wrote:

Are this the good one?


Mor

Your BITX must be V3.. Yes, order TDA2822M

What you ordered will be useful for other projects so its not a waste.



Raj

On the chip there stay? YWN3M2NB? ?UTG2822M? ?so did i buy the wrong chip
Thanks in advance
73,
Mor

There's a "Download the circuit diagrams" link on this webpage:?
? ??
but that link is broken.

I've attached the hi-res version of the Bitx40 schematic with Raduino.
There are some minor errors in the schematic, but this is the only one every published after the Raduino came out.
A few that come to mind:
? Anything labeled "BC849" is an MMBT3904 (a 2n3904 in a surface mount package)
? D15 and D16 are now a BAT54S dual schottky diode
? R106 is not stuffed, all three pins of that pot are shorted out
? L4, C93, and C103 are not stuffed
There might be one or two I missed, but I think that's most of it.

Jerry, KE7ER

Interesting, here is a 20-80pF >5kV?variable capacitor someone 3D printer using kapton tape as the dielectric.?



Looks like the designer of this is trying to use it to tune a magnetic loop and having issues with heating above 50 watts; judging from the comments section. So, kapton may be a low Q, high loss, material, too.

Kapton has gained a bad reputation for degrading, as an insulator, over time.?

I'll look around for a table that lists dielectric materials and their losses.

Tom, wb6b

Please order TDA2822 type chips. There are JRC equivalents which I prefer NJM2073D.

NTE7155 is another one

Raj

All,

I have been playing around with a BITX40/Raduino board set and have found it quite enjoyable except for the schematic.? When I blow it up to where these old eyes can see the symbols the component callouts are so fuzzy I can't read them? Is there a better schematic around somewhere (like in PDF)?? I would like to print a schematic large enough to put voltage readings, etc. on to aid in future troubleshooting if needed.

73,

Justin B.