Re: LTSpice simulation of uBitx Power Amp

Jerry Gaffke

Have now uploaded version two of the simulation:
https://groups.io/g/BITX20/files/KE7ER/WA2EBYandUBITX_2.asc
https://groups.io/g/BITX20/files/KE7ER/WA2EBYandUBITX_2.pdf

Has the following changes:
Quiescent drain current reduced to 10ma on both.
Added a switching mechanism to show response at both 7 and 30 mhz with a single run.

Observations:

Power out on WA2EBY is still much lower at 30mhz than he reported in his QST article.
Input impedance at 30mhz falls to 12 ohms, which is the primary factor here.
If Vin source impedance is reduced from 50 ohms to 0 ohms, then 30mhz output exceeds 7mhz output.

Removing C3 increases output a bit at both 7 and 30mhz

L3 helps make the exciter see a resistive load, but doesn't help much.

I'm moving on to other things.
Let me know if anybody figures out why my model of the WA2EBY amp shows the output to be so much lower at 30mhz
Here's my notes on how I got the WA2EBY inductor values, includes a python script for single layer coils:

#   Single layer coils, wheeler formula:  Henrys = 0.001 * N**2* R**2 / (228R + 254L)
#   where N is number of turns, R is radius in meters, L is length in meters (>0.8r)
def h(n, d, w): # turns, form diameter in inches, wire diameter in inches
length = w*n/39.37 # length of coil in meters, assuming close wound
radius = (d+w)/2/39.37 # radius of coil from middle of wire in meters
return(henries)

L1, L2   9-1/2 turns #24 enameled wire, closely wound 0.25-in. ID       >>> h(9.5, 0.25,  0.02):  5.285e-07 = 0.5285uH
L3       3-1/2 turns #24 enameled wire, closely wound 0.190-in. ID      >>> h(3.5, 0.190, 0.02):  8.222e-08 = 0.0822uH
T1       10 bifilar turns #24 enameled wire on an FT-50-43 core  uH=(AL*Turns**2)/1000  AL=440     (440*100)/1000 = 44uH/winding
T2       10 bifilar turns #22 enameled wire on two stacked FT-50-43 cores. AL doubles (880*100)/1000 = 88uH/winding
T3       Pri 2 turns, sec 3 turns #20 Tefloncovered wire on BN-43-3312 balun core. AL=7000    (7000*4)/1000=28uH, (7000*9)/1000=63uH

Jerry,  KE7ER

On Sun, Feb 4, 2018 at 10:21 pm, Jerry Gaffke wrote:

I've now uploaded an LTSpice simulation schematic file that allows easy comparison of the uBitx and WA2EBY finals,
https://groups.io/g/BITX20/files/KE7ER/WA2EBYandUBITX.asc
https://groups.io/g/BITX20/files/KE7ER/WA2EBYandUBITX.pdf

I haven't played with it too much, haven't taken any notes.
But here's what I think I'm seeing:

The WA2EBY does perform better.
Power in is about the same between the two, power out from the WA2EBY is generally a factor of 3 greater.
The gates on the WA2EBY have nice sine waves, the uBitx is quite distorted there by capacitive loading.
Input impedance on both is about 50 ohms at 7mhz, both go down to about 12 ohms at 30mhz,
as determined by monitoring the voltage after the 50 ohm source impedance resistor.
Both show a 4x power increase when switching from 30mhz to 7mhz, more than I would
have expected on the WA2EBY, perhaps I have some wrong values on the inductors?
The IRF510 model assumes worst case for Rds(on) and Qgate, though I doubt that's just too far off.

Jerry, KE7ER

Re: LTSpice simulation of uBitx Power Amp

Diver Martin <diver.martin@...>

> Let me know if anybody figures out why my model of the WA2EBY amp shows the output to be so much lower at 30mhz

To quote George E.P. Box, "All models are wrong, but some are useful."

Spice models are just that, models.  They're rarely right.  But they can tell you useful things about some of the mechanics of what's going on inside the system.

On Mon, Feb 5, 2018 at 10:40 AM, Jerry Gaffke via Groups.Io wrote:
Have now uploaded version two of the simulation:
https://groups.io/g/BITX20/files/KE7ER/WA2EBYandUBITX_2.asc
https://groups.io/g/BITX20/files/KE7ER/WA2EBYandUBITX_2.pdf

Has the following changes:
Quiescent drain current reduced to 10ma on both.
Added a switching mechanism to show response at both 7 and 30 mhz with a single run.

Observations:

Power out on WA2EBY is still much lower at 30mhz than he reported in his QST article.
Input impedance at 30mhz falls to 12 ohms, which is the primary factor here.
If Vin source impedance is reduced from 50 ohms to 0 ohms, then 30mhz output exceeds 7mhz output.

Removing C3 increases output a bit at both 7 and 30mhz

L3 helps make the exciter see a resistive load, but doesn't help much.

I'm moving on to other things.
Let me know if anybody figures out why my model of the WA2EBY amp shows the output to be so much lower at 30mhz
Here's my notes on how I got the WA2EBY inductor values, includes a python script for single layer coils:

#   Single layer coils, wheeler formula:  Henrys = 0.001 * N**2* R**2 / (228R + 254L)
#   where N is number of turns, R is radius in meters, L is length in meters (>0.8r)
def h(n, d, w): # turns, form diameter in inches, wire diameter in inches
length = w*n/39.37 # length of coil in meters, assuming close wound
radius = (d+w)/2/39.37 # radius of coil from middle of wire in meters
return(henries)

L1, L2   9-1/2 turns #24 enameled wire, closely wound 0.25-in. ID       >>> h(9.5, 0.25,  0.02):  5.285e-07 = 0.5285uH
L3       3-1/2 turns #24 enameled wire, closely wound 0.190-in. ID      >>> h(3.5, 0.190, 0.02):  8.222e-08 = 0.0822uH
T1       10 bifilar turns #24 enameled wire on an FT-50-43 core  uH=(AL*Turns**2)/1000  AL=440     (440*100)/1000 = 44uH/winding
T2       10 bifilar turns #22 enameled wire on two stacked FT-50-43 cores. AL doubles (880*100)/1000 = 88uH/winding
T3       Pri 2 turns, sec 3 turns #20 Tefloncovered wire on BN-43-3312 balun core. AL=7000    (7000*4)/1000=28uH, (7000*9)/1000=63uH

Jerry,  KE7ER

On Sun, Feb 4, 2018 at 10:21 pm, Jerry Gaffke wrote:

I've now uploaded an LTSpice simulation schematic file that allows easy comparison of the uBitx and WA2EBY finals,
https://groups.io/g/BITX20/files/KE7ER/WA2EBYandUBITX.asc
https://groups.io/g/BITX20/files/KE7ER/WA2EBYandUBITX.pdf

I haven't played with it too much, haven't taken any notes.
But here's what I think I'm seeing:

The WA2EBY does perform better.
Power in is about the same between the two, power out from the WA2EBY is generally a factor of 3 greater.
The gates on the WA2EBY have nice sine waves, the uBitx is quite distorted there by capacitive loading.
Input impedance on both is about 50 ohms at 7mhz, both go down to about 12 ohms at 30mhz,
as determined by monitoring the voltage after the 50 ohm source impedance resistor.
Both show a 4x power increase when switching from 30mhz to 7mhz, more than I would
have expected on the WA2EBY, perhaps I have some wrong values on the inductors?
The IRF510 model assumes worst case for Rds(on) and Qgate, though I doubt that's just too far off.

Jerry, KE7ER

--
Martin Held - AE7EU
http://ae7eu.com/
-------------------------------------------------------------------------------
If there aren't any questions, then what is there to learn?

Re: LTSpice simulation of uBitx Power Amp

K9HZ <bill@...>

Mod ls are Starting points without spending \$.

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

Owner – Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

email:  bill@...

On Feb 5, 2018, at 12:47 PM, Diver Martin <diver.martin@...> wrote:

> Let me know if anybody figures out why my model of the WA2EBY amp shows the output to be so much lower at 30mhz

To quote George E.P. Box, "All models are wrong, but some are useful."

Spice models are just that, models.  They're rarely right.  But they can tell you useful things about some of the mechanics of what's going on inside the system.

On Mon, Feb 5, 2018 at 10:40 AM, Jerry Gaffke via Groups.Io wrote:
Have now uploaded version two of the simulation:
https://groups.io/g/BITX20/files/KE7ER/WA2EBYandUBITX_2.asc
https://groups.io/g/BITX20/files/KE7ER/WA2EBYandUBITX_2.pdf

Has the following changes:
Quiescent drain current reduced to 10ma on both.
Added a switching mechanism to show response at both 7 and 30 mhz with a single run.

Observations:

Power out on WA2EBY is still much lower at 30mhz than he reported in his QST article.
Input impedance at 30mhz falls to 12 ohms, which is the primary factor here.
If Vin source impedance is reduced from 50 ohms to 0 ohms, then 30mhz output exceeds 7mhz output.

Removing C3 increases output a bit at both 7 and 30mhz

L3 helps make the exciter see a resistive load, but doesn't help much.

I'm moving on to other things.
Let me know if anybody figures out why my model of the WA2EBY amp shows the output to be so much lower at 30mhz
Here's my notes on how I got the WA2EBY inductor values, includes a python script for single layer coils:

#   Single layer coils, wheeler formula:  Henrys = 0.001 * N**2* R**2 / (228R + 254L)
#   where N is number of turns, R is radius in meters, L is length in meters (>0.8r)
def h(n, d, w): # turns, form diameter in inches, wire diameter in inches
length = w*n/39.37 # length of coil in meters, assuming close wound
radius = (d+w)/2/39.37 # radius of coil from middle of wire in meters
return(henries)

L1, L2   9-1/2 turns #24 enameled wire, closely wound 0.25-in. ID       >>> h(9.5, 0.25,  0.02):  5.285e-07 = 0.5285uH
L3       3-1/2 turns #24 enameled wire, closely wound 0.190-in. ID      >>> h(3.5, 0.190, 0.02):  8.222e-08 = 0.0822uH
T1       10 bifilar turns #24 enameled wire on an FT-50-43 core  uH=(AL*Turns**2)/1000  AL=440     (440*100)/1000 = 44uH/winding
T2       10 bifilar turns #22 enameled wire on two stacked FT-50-43 cores. AL doubles (880*100)/1000 = 88uH/winding
T3       Pri 2 turns, sec 3 turns #20 Tefloncovered wire on BN-43-3312 balun core. AL=7000    (7000*4)/1000=28uH, (7000*9)/1000=63uH

Jerry,  KE7ER

On Sun, Feb 4, 2018 at 10:21 pm, Jerry Gaffke wrote:

I've now uploaded an LTSpice simulation schematic file that allows easy comparison of the uBitx and WA2EBY finals,
https://groups.io/g/BITX20/files/KE7ER/WA2EBYandUBITX.asc
https://groups.io/g/BITX20/files/KE7ER/WA2EBYandUBITX.pdf

I haven't played with it too much, haven't taken any notes.
But here's what I think I'm seeing:

The WA2EBY does perform better.
Power in is about the same between the two, power out from the WA2EBY is generally a factor of 3 greater.
The gates on the WA2EBY have nice sine waves, the uBitx is quite distorted there by capacitive loading.
Input impedance on both is about 50 ohms at 7mhz, both go down to about 12 ohms at 30mhz,
as determined by monitoring the voltage after the 50 ohm source impedance resistor.
Both show a 4x power increase when switching from 30mhz to 7mhz, more than I would
have expected on the WA2EBY, perhaps I have some wrong values on the inductors?
The IRF510 model assumes worst case for Rds(on) and Qgate, though I doubt that's just too far off.

Jerry, KE7ER

--
Martin Held - AE7EU
http://ae7eu.com/
-------------------------------------------------------------------------------
If there aren't any questions, then what is there to learn?

Re: LTSpice simulation of uBitx Power Amp

Jerry Gaffke

I suppose.
The LTSpice model of the IRF510 does assume worst case, perhaps that is part of it.
But the WA2EBY model is off from the performance reported in the QST article by more than I would expect when operating at 30mhz.
And the uBitx models pretty close to the performance we actually get.

Regardless, looks like we'd do well to hack the uBitx to use something closer to the WA2EBY circuit.
And if that doesn't give the required performance at 30mhz, then drive the IRF510's from a lower impedance source.
LTSpice is whispering to me that if driven hard enough, the IRF510's will do 30W at 30mhz.

Jerry, KE7ER

On Mon, Feb 5, 2018 at 10:47 am, Diver Martin wrote:
> Let me know if anybody figures out why my model of the WA2EBY amp shows the output to be so much lower at 30mhz

To quote George E.P. Box, "All models are wrong, but some are useful."

Spice models are just that, models.  They're rarely right.  But they can tell you useful things about some of the mechanics of what's going on inside the system.

BITX40 Low audio volume with 8.5V to board/Raduino

Steve

Hi gang.  So I thought I'd get stupid and add complexity where none is needed.  Radio: BTX40, 1.27.7 'ware, basic hardware mods.  I put a buck converter between the power switch and the leads that feed B+ to the board and the Raduino- thinking I'll save some power, or be easier on those parts, temp-wise- and adjusted the voltage to 8.5.  Now, the previously robust speaker output is much diminished, and the volume control has no effect after about half it's initial rotational travel.  If I adjust the B/C up to maximum- 11.7V- still low volume. If I de-fuse the B/C and jumper around it (note that the led on the b/c lights up when I do this) and use the bench power supply to reduce the V in to 8.5V, the audio is a bit lower than with 13.8V, but the volume control functions as normal.  Note that the radio and all the wiring is still spread out over the bench....Removing the B/C is the easy solution, but I'm just wondering.....Aloha, Steve WH6ST

Re: LTSpice simulation of uBitx Power Amp

Diver Martin <diver.martin@...>

Looking at the schematic, has anyone tried changing the turns ratio on T10, or monkeying with the preamp?  It would lower the drive level, but also lower the drive impedance.  One might also increase the resistance slightly of R90/93 (increasing the drive bias of the preamp stage, dangerous) or lowering the emitter degeneration resistors (R941, 911, 942 and 96) from 22 ohms to something like 10 ohms (Degeneration is useful here though, it provides linearity to the amplifier).

I use IRF530's in a different amplifier design that puts out 50W with about 3W in at 30MHz.  Not sure what the preamp stage is rated for, I'd assume ~0.5 to 1W tops.

On Mon, Feb 5, 2018 at 11:29 AM, Jerry Gaffke via Groups.Io wrote:
I suppose.
The LTSpice model of the IRF510 does assume worst case, perhaps that is part of it.
But the WA2EBY model is off from the performance reported in the QST article by more than I would expect when operating at 30mhz.
And the uBitx models pretty close to the performance we actually get.

Regardless, looks like we'd do well to hack the uBitx to use something closer to the WA2EBY circuit.
And if that doesn't give the required performance at 30mhz, then drive the IRF510's from a lower impedance source.
LTSpice is whispering to me that if driven hard enough, the IRF510's will do 30W at 30mhz.

Jerry, KE7ER

On Mon, Feb 5, 2018 at 10:47 am, Diver Martin wrote:
> Let me know if anybody figures out why my model of the WA2EBY amp shows the output to be so much lower at 30mhz

To quote George E.P. Box, "All models are wrong, but some are useful."

Spice models are just that, models.  They're rarely right.  But they can tell you useful things about some of the mechanics of what's going on inside the system.

--
Martin Held - AE7EU
http://ae7eu.com/
-------------------------------------------------------------------------------
If there aren't any questions, then what is there to learn?

IRF510 more Volts = more W?

Jim McKay

I could not find the answer on the forum but I apologize now if it has already been answered. Noting the need for an improved heatsink/s. Has anyone done any experiments with increasing the PA voltage  (brown wire) up 24V to see if the output significantly increases. I did this with a BITX40 for a significant increase in W.

Jim

Re: At long last!!

David Robertson

Sorry about that. My order date was December 16, 2017. Hope the rest of you that are waiting I hope you get your radio soon
73
Dave KD1NA

--
Dave Robertson KD1NA

Re: Diy oscilloscope

Joe Puma

I would like to get on of these and a real one not a knockoff but I’m trying to find one build already. I’m not afraid to build the kit but I’d rather get it built at the moment.

I’m also looking for a RF millivolt reader. I want to check some RF voltage points on my Yaesu for starters. It’s a good introduction for me to get started with using test equipment.

Joe
KD2NFC

On Feb 1, 2018, at 4:54 PM, Doug W <dougwilner@...> wrote:

On Thu, Feb 1, 2018 at 01:40 pm, Jerry Gaffke wrote:
Very nice of JYE-Tech to release all that, would be good karma to support them by avoiding clones.
It's more likely to work, and you are more likely to get support if it doesn't.
They specifically mention the SainSmart clone up on their website.
To build on Jerry's point, https://www.jyetech.com/Products/LcdScope/e138.php is worth a read.  I've been looking at these kits off and on and had no idea.
I've purchased SainSmart filament in the past, never again.

Re: IRF510 more Volts = more W?

Doug W

If you access the list from https://groups.io/g/BITX20/topics instead of an email client you will have access to the search function.  Searching for irf510 24v will yield enough reading to keep you busy for a while.  Best of luck with your experimenting.  Should your quest result in releasing the magic smoke, fear not, a search for irf510 replacement will get you back to good.

Re: Diy oscilloscope

Jerry Gaffke

JYE sells it with all surface mount parts installed, you still have to add the through hole parts.
Here's what might be a good RF probe, suitable for low level signals, use it with a dvm:

On Mon, Feb 5, 2018 at 12:23 pm, Joe Puma wrote:
I would like to get on of these and a real one not a knockoff but I’m trying to find one build already. I’m not afraid to build the kit but I’d rather get it built at the moment.

I’m also looking for a RF millivolt reader. I want to check some RF voltage points on my Yaesu for starters. It’s a good introduction for me to get started with using test equipment.

No receive audio from antenna, Bitx40

Lisa.beasley42@...

Bitx40 no receive audio at all when attached to an antenna or on a dummy load.  I have a speaker and headphone jack wired.  Baofeng mic and ptt are on separate 3.5 mm jack. VFO changes frequencies, Power comes on and appears to work as expected.  I have a 10 turn pot and made the modifications for tuning range within the options field.  Is there a description of basic troubleshooting with a multi-meter to test what continuity or amps should be present at certain points on the board or another way to narrow down the problem?

Re: No receive audio from antenna, Bitx40

KC9SGV <kc9sgv@...>

Hi Lisa,
Here....

Bernie,
KC9SGV

On Feb 5, 2018, at 3:02 PM, Lisa.beasley42@... wrote:

Bitx40 no receive audio at all when attached to an antenna or on a dummy load.  I have a speaker and headphone jack wired.  Baofeng mic and ptt are on separate 3.5 mm jack. VFO changes frequencies, Power comes on and appears to work as expected.  I have a 10 turn pot and made the modifications for tuning range within the options field.  Is there a description of basic troubleshooting with a multi-meter to test what continuity or amps should be present at certain points on the board or another way to narrow down the problem?

B C

I didn't think anyone used code anymore...its all FT8...hi hi
Brian K9WIS

---- "Charles D. Smith" <@ChasAI4OT> wrote:
One book at a time ... your “projects” book is all I can handle right now ... I’m hoping if I put it under my pillow, I’ll learn some code ;-)
On Feb 1, 2018, at 9:21 PM, Jack Purdum via Groups.Io <jjpurdum=yahoo.com@groups.io<mailto:jjpurdum=yahoo.com@groups.io>> wrote:

Jack, W8TEE

________________________________
From: Charles D. Smith <@ChasAI4OT<mailto:@ChasAI4OT>>
To: BITX20@groups.io<mailto:BITX20@groups.io>
Sent: Thursday, February 1, 2018 8:42 PM
Subject: [BITX20] First Arduino sketch loaded

nobody laugh ... (ok, go ahead) ... I just loaded and modified my first sketch ... so changing out “world” and putting in my town isn’t much of a change, it’s something. Plus, I varied the count too ... woohoo!
before I plug the computer into the raduino, I’m going to get a much better handle on this stuff! But it’s very exciting to a pencil and paper guy!
72/73 de Chas ai4ot.

Dave Bottom <ars.kd6az@...>

Helluva Rush Order 5 (Military version)
...And it was for  in a rush back during WWII

Lotsa fun radios can be found for almost nothing. This one free except cost of gas to go pick it up and restoration parts.

You can’t duplicate the smells as they warm the room. Part of the patina.

Dave WI6R

On Feb 5, 2018, at 10:40 AM, chris gress <Chrisg0wfh@...> wrote:

And to think I have 1 old ICOM I'm to poor for any else lol

On 5 Feb 2018 18:35, "Jack Purdum via Groups.Io" <jjpurdum=yahoo.com@groups.io> wrote:
One can get carried away, however...

Jack, W8TEE

From: Leland Lannoye <wa9aoe@...>
To: BITX20@groups.io
Sent: Monday, February 5, 2018 10:49 AM
Subject: Re: [BITX20] whistles in receive

There have been numerous articles in QST over the years on rebuilding these old rigs.  I found an article which I saved somewhere on building transistor substitutes for the tubes.  you could build them on small perf boards and set up a set of wires that corresponded to the pin out on the tubes.  At one time, someone was making modules to replace all the low power and receiving tubes on the Collins S line.  That was at least 40 years ago.  I don't do well on a lot of these tiny connections anymore due to age and aging eyes, but my history skills are still largely intact.
Lee, WA9AOE
PS: Still awaiting shipment on my Bitx.
On 2/5/2018 10:40 AM, Ashhar Farhan wrote:
The warm smells of an HRO steaming up... is there any hotroding one can do to these rigs?
- f

On 5 Feb 2018 12:02 am, "Leland Lannoye" <wa9aoe@...> wrote:
I am sitting here reading some of this information and studying the new technology.  When I was young (at leas 50 years ago), solid state technologies were either in their infancy or still a dream.  Our rigs were two pieces of equipment, a receiver and a transmitter with a variety of accessories.

Most of our receivers for those of us who were not well heeld in the financial area were of the single conversion genre with an if frequency of 455 kHz.  With little preselection capability, this relegated the ham bands 20 mtrs and above useless with hetrodyne images from frequencies 910 kHz either above or below the desired reception point. There, in that day, were three remedies to fix this. The first two were:

1.)  add a really selective high gain preselector to tune the offending images out

2.)  raise the if to something on the order of 1600 kHz which left bandpass selectivity at a substantial disadvantage.

The third option, and the most expensive in its day was double (or, even triple) conversion.  If  you were able to pay the 1958 price of over \$300, you were in and there were few difficulties thereafter until the receiver aged and developed some bad shield grounds or worse.  The second or third conversion local oscillator would provide a cornu copia of birdies of one type or another. These included signals that were always there, I know the newer designs with balanced mixers and the like have few of these problems, but, it is worth considering.

An aging ham from way back.

Lee, WA9AOE

---
This email has been checked for viruses by AVG.
http://www.avg.com

 Virus-free. www.avg.com

Re: IRF510 more Volts = more W?

Nick VK4PP

HI,
I did this last night with the uBITX, went from 13.8 to 24v. and only saw an increase of +-2w.

80m 24v=12w 13.8v=10w
40m 24v=7w 13.8v=9w
20m 24v=3w 13.8v=4.5w
10m 24v=1w 13.8v=2w

Also cause weird display glitched during TX....
Thoughts?
73 VK4PLN

Re: uBITX Firmware (CEC) 0.30 released (Test version).

Jack Purdum

Hi Ian:

I was wondering if you had plans to convert the support files for your software to *.cpp files from their current *.ino secondary file names (except for ubitx_30.ino)?

Jack, W8TEE

Allard PE1NWL

On Mon, Feb 5, 2018 at 07:56 am, Jerry Gaffke wrote:
One of my earliest memories at about 3 years of age, maybe less, is being fascinated
Peering around in back, face pressed against the wall, trying to see what was inside
and figure out how it worked.
Funny, that's exactly one of my earliest memories too.
I used to peek trough the holes in the rear panel. Inside was a mysterious glow and a warm smell came out:

One day I turned the dial and strange beeps came out. My dad told me they were messages from saylors far away.
I never lost my fascination for radio waves since.

73 Allard PE1NWL

Re: Anyone (US Only for now) need a uBITX Raduino repaired?

Jim Sheldon

That DOES present a problem - LOL.

I found that one does NOT want to power the Nano using the Vin pin if you are using an external supply greater than 12VDC!  The on board LM1117 regulator can't take that with the load of the processor and the I/O on it.  Smoke, fire and flames in the regulator - overvoltaged the processor on the Nano, put more than 5 volts onto the I2C bus so it wiped out the Si5251 Clock chip as well.

I got a real education in replacing the 5351 - LOL.  I have a cheap hot air rework station and it did a nice job removing the dead chip.  I have been playing with the idea of possibly breadboarding a Raduino and have some carrier PC boards for the 5351's.  Still have to solder the chips on the boards though.  I bough a handful of 5351A's from Digi-Key for 91 cents US apiece.

The way to go was Chip Quik's "Tack" flux - not cheap but 10ml for \$20 bucks will last a LOOOONG time.  Dab of it on each pad, position the chip carefully over it's pads and using a needle point tip on my soldering iron, tacked each pin to the board.  I made up a probe for my DVM using a small sewing needle and was able to confirm continuity and no shorts on all the pins.  Programmed a new Nano and replaced the one that burned up (put machined pins and sockets on things this time).  Everything fired up and ran just fine.  Just after I built the test fixture, I read the frequencies of the clocks on my nicely calibrated uBITX and wrote them down.  With the test set, I can go into Factory Alignment mode and with a freq counter attached to the Clock 2 output, I can actually set the frequency accurately and save it.  The BFO can be read on clock 1 and I had those figures too so setting it to the right frequency was a breeze.  After the repair, I re-installed it in the uBITX, tuned to WWV at 5.000.00 MHz (the only one I can hear in Kansas during the daytime) and I was only off by 150 Hz.  Sure saved a lot of time being able to pre-calibrate the clocks outside of the radio!

The only drawback is - the clocks have to be calibrated to the specific radio for accuracy, due to the variations in crystal filters.  You can, however get very close so if I had to replace a Nano for someone, I could pre-calibrate the clocks to close proximity of what they should be and the user could fine tune them in his/her rig.

Jim - W0EB

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