开云体育

I had my U4B transmitting using a 3.7 Volt battery connected to the Battery and Ground terminals and I wanted to change the call sign as a test so I plugged-in my USB cable.

It no longer is able to enumerate on the USB bus.

I tried three different cable and have tried with and without the battery connected.

Windows says "Device descriptor request failed"
Linux says about 40 different things that amount to the same thing, failure to get the device descriptor.

I can still enumerate my other U4B on the same machine and the same cables.

Does anyone have any idea if this is something I should not have done?

Uh oh!

Alan KC1QHV

Alan?
Disconnect the battery?
Do not try to run from both battery and Usb power at the same time
Dave VE3KCL

Alan?
It is possible that you over drove the usb output on your computer usually they are set to kick out at .5amps .... it may come back after it cools down?
By hooking up usb and battery at the same time you have usb 5v dropping through a s4 diode trying to charge a lipo battery which could have exceeded the usb current limiting device on your computer usb drive ... try computer reboot and try the usb only with a different usb plug on the computer... it also may have fried the small s4 diode on the break off board.... check this diode with a meter and if it is open just replace with another schottky.?
Dave VE3KCL

Thank you Dave. I have noticed some strange behavior with my USB port.

If I cut the 5V from the USB will the computer still send data? I would like to monitor things while I am testing solar cells.?

Colin
K6JTH

Hi Colin
It may not be advisable to run 2 power sources at the same time.( the solar input is protected by a blocking diode but the battery input is not and can cause trouble)
When connected to the USB the U4B senses this and I believe runs the processor at a higher clock speed to generate the USB connection throwing off the? power consumption values.?
Also when running from the USB power, the STM32 has to do a lot work updating the monitor etc. and hence the timing is a bit slower... you could be misled by the results.
For instance Transmitting the QRSS glyph and ident takes 56 seconds on battery power and 62 seconds on usb power ... this could cause a problem, if the next wspr tx is supposed to start at the top of the minute and now it is 2 seconds late.?
What I do to evaluate solar cells for the U4B is simply use a series ma meter and a volt meter in the solar circuit on earth into a fixed resistor load and then adjust the numbers for the cold at float which will produce as much as 20% more power.
You need about? 56ma for high power tx mode and as high as 40ma to lock the gps and transmit low power ... If you have those numbers @ >3.3v the solar cells should work fine.
Dave VE3KCL

IT'S WORKING!

After some rest, I tried again this morning and noticed that if I held the USB cable juuuuuuuust right I would get a connection.

I looked under the microscope and it looks like three of the USB connector pins are not completely soldered, so I touched them up and it's all fine now. They are sort of soldered underneath the pin, but it's not real great. My other UB4 connector soldering looks even worse, so I'll touch that up also. MAN, the pins on that connector do NOT want to take solder even with flux. #supplychain

Anyway, I'm back up and running and won't power with two supplies at the same time again just for safety.

Thanks Dave,

Alan KC1QHV

One of my U4B usb only works when I apply pressure to it. Unfortunately I don’t have the skills to be able to solder it. I did put a ticket in about it, but haven’t heard back yet.?

Ted KG5TED?

My USB connector was getting flaky after a 100 or so insertions. ;) I replaced it. I didn’t think of touching a soldering iron to the connections first. If you have hot air it’s a quick replacement. I really wish I had ordered two. They are a ton of fun. If I hadn’t told my 11 year old about it I think I would keep it till more were available.?

I now have a short USB extension and I leave it plugged into the U4B.

Colin
K6JTH

Yes _ I had trouble early on with the USB port which I attempted to repair and somehow caused a short which burned out D3. i replaced that with an ordinary diode - and got it going again, but then it went flakey about starting up. Sometimes the diode would light when I applied power and sometimes not. I got it going again somehow, and had lots of fun with it for a few days, but now it has gone dead again - coincidentally - maybe - after I connected both the depleted battery AND the USB power - which I see David warns against below here. I can see how a 3.3v lithium battery might suck a lot of power through D3 and burn it up now he has made it obvious, but my D3 is a much more beefy one, and in any case, the power after the 3.3v regulator is there. My U4b is just apparently dead. Correct voltage on the micro controller, but no current being drawn.

I need to get my x 12 jeweller's loup out again and see what is not where it should be.

Any hints gladly received. It was great fun, and I want it working again, but I am foundering about n the dark really.?

On Sat, May 28, 2022 at 09:28 PM, Colin Kaminski wrote:

Thank you Dave. I have noticed some strange behavior with my USB port.

If I cut the 5V from the USB will the computer still send data? I would like to monitor things while I am testing solar cells.?

Colin
K6JTH

I think you will find that if there is no power at the USB port, the micro controller will not open the data lines to the usb port. I came across this after my cack handed effort to replace D3 after an 'accident' I caused when trying to fix the serial port connection.? To replace it, I fitted a through the hole diode above the board, and inadvertently disconnected R7 which goes to pin 40 of the micro controller from the 5 volt line of the USB port. I think this connection allows the controller to sense that the USB port is connected. Once I repaired the damaged track, the serial port opened fine. Without that 5v input to R7 and pin 40 on the controller, it won't open.

I am working way beyond my vision and skill trying to fix this tiny unit. Surface mount is way beyond my ability.

The other easy to damage point is C15. It is very close to the HF antenna and can easily be caught up while soldering the dipole. I had mine stick to the soldering iron while trying to burn off the enamel on my dipole.?

Colin
K6JTH

On soldering wires to the U4B terminals.... this is how I manage it....

I never put the soldering iron? tip on the U4B terminals for more than a second.
First I put a small dot of solder on the U4B terminal to be connected, tinning it so it has a slight dome of solder on the terminal.
Second I tin the end of the wire to be connected ...this is done far away from the U4B (burning off enamel should not be done on the U4B terminals)
After the wire to be connected is tinned I cut it so only 1/16" of the tinned wire is showing past the enamel or insulation.
I then place the tinned wire over the terminal to be soldered and touch the terminal with a freshly tinned soldering iron tip.(about 320 c)
If all goes well the connection is made in about 1/2 a second .
Then I give the wire a small tug to confirm it has connected to the terminal.
Dave VE3KCL

On Mon, May 30, 2022 at 04:34 AM, <tony.volpe.1951@...> wrote:

I want it working again

Hey Tony, if you ship it to me I'll take a shot at getting it working again and ship it back to you. No charge.
I have a nice stereo microscope and a good fine-tip soldering iron.
And...... I can't make it any worse can I?

My info is on the QRZ website or in the FCC database.

73 Alan KC1QHV

Alan. What a fine gentleman you are. That is a very kind offer and I really appreciate it. Just let me persist with it a tiny bit longer and if I can't find the problem myself, I will be very glad to send it to you, and I will be in your? debt, whether you manage to fix it or not.? In these times of horrible, needless wars, this kind of genuine offer to help a fellow traveller, restores faith in the goodness of human nature.

Thanks again.

I will be in touch after some more peering with my jeweller's loupe.

73s?

Tony G0BZB

YAY! It's fixed!!!?

I have an update on my U4B. It is fixed and working again. I had two issues. The first to appear was that the micro usb port was flakey - pretty much from the start. I attempted to repair it and made things worse, but now, since the tracker is for garden or remote use only and not for flying, I have wired in a cut off usb cable to the board. I had to select new places to wire it to, because there is no way I am capable of soldering the four wires from teh cable to the tiny tracks the micro usb socket used. I can't see well enough, and I don't think my hand is steady enough. Fortunately, the snap off holes are plated through and connect to the tracks I needed to access.

One problem I had with this USB cable fix, was that there certainly seem to be at least two species of USB wire colour schemes, using red, green white and black wires. Black and Red are universally consistent, but in some leads, the Data + and Data? the colours can be reversed. Some googled images show white as D+ and others Green.? Of course, I took a gamble based on the number of examples I found of each and picked the commonest which showed white as Data + and of course - sods law, my cable was wired the other way...... The serial port on the U4B ignored my connection requests, so I reversed the data lines and it works very reliable now. Opens every time and stays open which was far from the case with mine from day one.

My second problem was that the unit would not start up for long periods and then it would do and would work fine for a day or two or a few hours and then it went off again.The symptom was that when I connected power, nothing happened and the red LED did not light up. Normally, the current draw for the unit is around 36mA (on mine at least) but when mine was in this dead condition, it systematically drew 68mA. The 8MHZ clock was working, but I conjectured that the micro controller was not running, or had somehow stalled during start up. I think I remember problems with broken QCX family where the micro controller would stall on start up if the SI5351A was faulty and not responding to polling. I half suspect this might be why mine would not start.?

I toiled over this and bored poor Dave in Toronto with emails, which he patiently answered and made suggestions about how to recover things. In the end, I believe the issue was an intermittent connection on the?SI5351A. Poking around this chip with a tiny, very stiff watch oiler, seemed to make the dead thing rise again like Dracula. Eventually I decided that pin 7 needed reflowing, which I did with some trepidation given the 0.5mm pin spacing, but it has worked solidly for a few days now and has been turned on and off quite a few times and has started up every time without fail. As to why the synthesiser chip would not start up, pin 7 is one of two connected to +3.3v, so maybe that was why it seemed dead.

So - I'm really pleased to have it back up and running again, it having spent at least a fortnight in my scrap box, only to be dragged out again and tortured some more with my rather cack handed manual and visual skills. It is working way beyond what I expected in terms of 27mW DX. I have it on? a weird doublet aerial with one leg a quarter wave at twenty, and the other a quarter wave at forty meters, and it is regularly getting across the Atlantic on twenty meters during the night. Some transmissions are getting as many as 28 spots in Europe with conditions of SFI 101, A index 4, K index 1.?

Best of all, I can now play with the programming and band changing easily since I have a sound serial connection, and that stuff is really interesting.?

This is a 24 hour snapshot of the 2054 spots I had today.