Since I run an EBY amp since 2006 you must have mis-read.? In the files section
I've even posted his articles back around 2010 and copied to this iteration years
ago. Still there.

The ubitx is not run that low, spec is 100ma per.?

The irf510 like all fets has a considerable hook at low gate to source voltages.
If the gate voltage is platted against the drian current the linear window is above
100ma and below saturation or about 4A.? Below that in the low end under 100ma?
drain current he gate voltage is not linear at all from start of conduction to the?
100ma range and? that makes for very non linear near cross over.? Class AB1
is more like 80-150ma but it is very toplology dependent.

His (WA2EBY) minimum was 50 ma per device for CW and testing put it higher
near 100ma per device for SSB to get a decent IMD at 28V.? I find mine
comfortable at 125 ma per device and the two tone testing is good enough at
about -28dbc.? However that design has the features needed for linear operation
including independent device bias,??current sourcing transformer for the drains
and large ferrite for the output transformer.

At 100ma per you only talking a standing power of 2.8W at 28V per device,
if that gets warm the heatsink is inadequate.?

So saying a specific current, especially low under 100ma, is inadequate
for linear use without testing questionable.? Especially for an amp designed
for class C use.? I do not say it cant be linear but at low bias its highly unlikely.

I have one on the way so testing will happen.

Allison

--
---------------------------------
No direct email, it goes to bit bucket due spam

I?I bought this case (S06A):?
It is not a real bargain but it comes complete with useful accessories

Cheers,
Diego I8TIF

Jerry, Sarma, Gordon,

Wow, am I confused.? I purchased 12 August 2019 and I thought it was a V5 however after Jerry's response I looked and it is a V4.? My bad for not checking things better.? Live and learn.

I am using a stereo cable I bought on ebay cheap.? After your responses I decided to check the 3.5mm connectors to see if there could be a short there.? Well, there are only 2 wires in the cable and shield and ring are connected together.? Lesson, don't buy cheap cables on ebay.? I will order some quality stereo cables from Amazon and see how things go.

Thank you so much for your responses.

Vince

On 12/16/2019 12:46 PM, Gordon Gibby wrote:

Are you DC shorting out the output with a transformer in the sound card??

On Dec 16, 2019, at 12:07, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

I'd guess your USB soundcard cabling is somehow (almost) shorting out the audio from that 2822 chip.
Look for a short.
Perhaps add an 8 or 10 ohm resistor in series with the TDA2822 to protect it from shorts like that.

The TDA2822 amp was used on v3.
Some discrete transistors were used on v4.
On v5, as Sarma has stated, the trusty (crusty?) old LM386 was used.

If you have a TDA2822 chip installed, it is probably v3.
A search of the forum for 2822 will reveal that a few v3 uBitx boards went out
with a WX branded TDA2822.? This clone of the TDA2822 works fine up to about 8v,
above 8v it can sometimes self destruct.? ?If you have a WX branded TDA2822 on
your board, I suggest you get an NJM2073D ordered from a reputable distributor
It is pin compatible with the TDA2822, works fine, good to 15v or so.

The original TDA2822 in the DIP package from ST is no longer available,
though ST does still sell it in an SOIC.
There are a half dozen different makers of clone TDA2822's, many of them work fine.

Some of the clones work ok but only with a maximum supply voltage of around 6v.
With the WX TDA2822 clone operating at 12v in the uBitx, the chip might work fine
for weeks and then suddenly decide to blow bits of silicon across the room.


A fun bit of trivia from?
? "The LM386 was invented by Ernie Leroy Long at Motorola in 1969. It was originally for part of a fuel injection system for a Ford Car."

If true, I assume it went by a different name at the time.
I'm a bit suspicious, a google for "LM386 Ernie" gets many copies of exactly the above phrase with no further information or attribution.
The "LM" prefix suggests National Semiconductor, perhaps it had a different name coming out of Motorola.

Jerry, KE7ER
?

On Mon, Dec 16, 2019 at 07:10 AM, V Zecchinelli wrote:

Good Morning,

I have a quick question on FT8 with uBitx V5 using USB soundcard (7.1 Channel).? Even with the volume of uBitx set very low the 2822 audio amp gets very hot and if volume set over 1/4 it will fail catastrophically.? On phone I can listen to the radio all day with no issues.? Seems odd.? Anyone else seen this problem?

Thanks,
Vince

Farhan,

No its not.? You need to be more than 100ma to get sorta on the linear part of the IRF510 bias curves.

At minimum bias you are on the very curved part of the gate threshold curve and the IMD will be poor with
crossover distortion.? Also we are not switching as its linear from transistor to transistor its complementary.
?
---------------------------------
No direct email, it goes to bit bucket due to spam