See page photo below

You definitely have the square wave available at pins 4 and 10. Your DVM is seeing a 50% duty cycle 3.3 volt square wave as about 1.7 vdc there.  But pin 5 should be 0v on RX and 5 volts on transmit. You are showing 0 volts in both states. With power off, Check for a short to ground from pin 5 of IC3. And check solder joints in the area of IC3. And while you’re at it, check for continuity between  IC3 pin 12 (and 13) to IC2 pin 14. If this is open, it will hold IC3 in the stuck mode you are describing. 

Good luck … Ron

On Mon, Oct 4, 2021 at 16:36 W8NNC <Bobplow8809@...> wrote:

See page photo below

Thanks Ron. I will check it out and let you know what I find. 

On Mon, Oct 4, 2021, 8:20 PM Ronald Taylor <wa7gil@...> wrote:

You definitely have the square wave available at pins 4 and 10. Your DVM is seeing a 50% duty cycle 3.3 volt square wave as about 1.7 vdc there.  But pin 5 should be 0v on RX and 5 volts on transmit. You are showing 0 volts in both states. With power off, Check for a short to ground from pin 5 of IC3. And check solder joints in the area of IC3. And while you’re at it, check for continuity between  IC3 pin 12 (and 13) to IC2 pin 14. If this is open, it will hold IC3 in the stuck mode you are describing. 

Good luck … Ron

On Mon, Oct 4, 2021 at 16:36 W8NNC <Bobplow8809@...> wrote:

See page photo below

On Sat, Oct 9, 2021 at 08:50 AM, W8NNC wrote:

With an analog ohmmeter,  junction D 5, C 52 is 0 ohms. If you expand the photo below I see a fine trace joining 2 traces. Could this be a ground fault? 

Is this a Rev 1 or Rev 2 board?? 

Looking at the top of C52, looks like a blob of solder shorting the two ends.  Looks like TX signal output from pin 11 is being shorted to ground...

73
km6wt

Hi, sorry for the slow response this morning. Yes, I think you found the problem there. C52 shorted will cause the TX line to be pulled down to one diode voltage drop above zero volts. That will disable the transmitter. That shorted solder blob on C52 must be the culprit. Some of the other joints in the area don't look too good. Lightly and quickly apply a hot iron to the top of C52 to remove the short and try things again. You may have to clean up some of the other joints if other problems arise, but that one issue is the prime one most likely casing your current issue. Good luck 73 .. Ron

On Sat, Oct 9, 2021 at 1:29 PM Mont Pierce KM6WT <de.km6wt@...> wrote:

On Sat, Oct 9, 2021 at 08:50 AM, W8NNC wrote:

With an analog ohmmeter,  junction D 5, C 52 is 0 ohms. If you expand the photo below I see a fine trace joining 2 traces. Could this be a ground fault? 

Is this a Rev 1 or Rev 2 board?? 

Looking at the top of C52, looks like a blob of solder shorting the two ends.  Looks like TX signal output from pin 11 is being shorted to ground...

73
km6wt

I see what you mean. I will try tomorrow.  What about that hair like trace between 2 larger traces to the right of the capacitor? Is that a correct trace?

On Sat, Oct 9, 2021, 4:52 PM Ronald Taylor <wa7gil@...> wrote:

Hi, sorry for the slow response this morning. Yes, I think you found the problem there. C52 shorted will cause the TX line to be pulled down to one diode voltage drop above zero volts. That will disable the transmitter. That shorted solder blob on C52 must be the culprit. Some of the other joints in the area don't look too good. Lightly and quickly apply a hot iron to the top of C52 to remove the short and try things again. You may have to clean up some of the other joints if other problems arise, but that one issue is the prime one most likely casing your current issue. Good luck 73 .. Ron

On Sat, Oct 9, 2021 at 1:29 PM Mont Pierce KM6WT <de.km6wt@...> wrote:

On Sat, Oct 9, 2021 at 08:50 AM, W8NNC wrote:

With an analog ohmmeter,  junction D 5, C 52 is 0 ohms. If you expand the photo below I see a fine trace joining 2 traces. Could this be a ground fault? 

Is this a Rev 1 or Rev 2 board?? 

Looking at the top of C52, looks like a blob of solder shorting the two ends.  Looks like TX signal output from pin 11 is being shorted to ground...

73
km6wt

On Sat, Oct 9, 2021 at 03:32 PM, W8NNC wrote:

What about that hair like trace between 2 larger traces to the right of the capacitor? Is that a correct trace?

No, mine does not have that seemingly tiny trace.


I was leading up to that with my question:  Is this PCB a Rev 1 or Rev 2 board?


After you remove the blob of solder on top of C52, use your meter and test continuity from D5/C52 junction to ground.

Repairing Manufacturer issues like solder bridges on SMDs and shorted traces under the solder mask is Not something we should have to do.  Hans certainly understands that there have been some manufacturing issues (especially with Rev 1 PCB).  If you find more issues like these you should direct email Hans and ask for advice.  He will gladly work with you on resolving manufacturer issues.

It does sound (and look) like this is a Rev 1 board, or otherwise somehow missed being tested in Hans' really cool test jig.


I hope these are the only two manufacturer issues you have with your mini, but, be prepared to find others.  Certainly whether if you want to work your own way through them, or contact Hans, that's your choice.   :)



73
km6wt