ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
esc to dismiss
Re: Special considerations when sourcing replacement capacitors?
#qmx
|
Sent fromj my iPhone
Re: My QMX+ has a .3 ohm short on VDD
Dear David,
Board tapping is a good method in finding an intermittent connection sometimes. I have done this with some success in the past. You might help narrow down the area using a narrow insulated “tapper” instead of a finger, like (for example) a chopstick. Then you can nudge various components individually or board areas until you find it.?
I think you are getting close.
73,
Gregg W7GRM
|
Most devices are tested at the die stage of manufacture, but not many devices are 100% tested after packaging.? ?Over 50 years of designing and have pcb assemblies made, the failure rates are extremely low.?
Sent from
toggle quoted message
Show quoted text
Wolfgang Pauli once said to Niels Bohr after a lecture "Your idea is crazy, but is it crazy enough?".
My kit arrived Monday, and I've been finishing a 1.25m repeater before starting (think of a horse hanging their own carrot on a stick), but I opened the box to examine the packaging.
It would seem to be difficult to damage the chip once it's mounted on a board with ~1000 uf of bypassing. TI puts its usual 2 kV input static protection on this chip. So one has to work some to break the thing.
Hans, if you don't see such a problem with the QRP Labs assembly crew, I would posit that the issue could be static buildup inside the packaging, during shipping. Every little jostle rubbing the bubble wrap on the cardboard...
A possible solution could be as simple as antistatic bagging the main board for shipping.
|
That leaves me one idea to explore, but I'll have to build the kit and measure transients to check it.
|
Re: My QMX+ has a .3 ohm short on VDD
Dear Greg.
My resistance measurement comes and goes.... when it isn't .4 ohms it is about 2.4kohms... tapping the board makes it change.? I have gone back to the work bench and rechecked some solder joints... But so far I have not been able to locate the joint that is either shorting to to something or something internal in the board is shorting it out.? It is a 5 layer board and? may be having an internal short in there.?? With the type of construction that is very unlikely but may be possible.?? My original software load may have been compromised by the board shorting during the upload.? So I may try to manually redo it when the shorts are not there..? (neat trick if I can pull it off)? the first upload may have been interrupted.? Ludwig sent me so really good information that I didn't know existed on how this all works.? What I see is the 3.3 regulated is on the linear regulator and the 5V is High on the diagnostic but read 4.6 or 4.8 on my meter when I test it externally.? I am running on a 8V reduced voltage and going to stay that way until I can find the short on the 3.3v supply.... or at least get the 3.3V up on the? SMS power supply.?? Lots of things to check and a busy day today.?
Take care and have fun.?? Thanks for the hints.
73 Dave WA5DJJ
|
In my case, I went out of my way to ensure that I had proper ESD procedures in place when I opened and assembled my kit. Wrist strap, anti-static mat with grounds. The unit powered up perfectly the first time, no problems except for a bad pcm1804. I am convinced
that the chip was DOA.
Note that there are a variety of failure modes. That is telling us something.
Tony
AD0VC
toggle quoted message
Show quoted text
Both my QMX builds came in an anti-static bag.
The instructions do say to observe ESD precautions, but the boards see quite a bit of handling by the builder to separate the various sub-boards and file down the rough edges.? I know I personally wasn't observing ESD precautions at that particular juncture
in the building process, but humidity levels were fairly high when I was doing so.?? Or perhaps some builders don't have soldering equipment with grounded tips?? It certainly is an enigma...
72 de Russ, va3rr
On Thu, Jul 11, 2024 at 10:16 AM, Chuck AI7SY wrote:
> A possible solution could be as simple as antistatic bagging the main board
> for shipping.
|
Hi All
I finished my QMX+ build on June 28. After some tweaking on the LPFs it was on the air and working well.
I worked the 13 Colonies Special event? with the QMX+, worked all 13 colonies and WM3PEN. So a? clean sweep in digital mode.
I want to thank Hans for the work he puts into the kits. I can hardly wait to see what is next!
72
Bill
KA3RMM
|
Both my QMX builds came in an anti-static bag.
The instructions do say to observe ESD precautions, but the boards see quite a bit of handling by the builder to separate the various sub-boards and file down the rough edges. I know I personally wasn't observing ESD precautions at that particular juncture in the building process, but humidity levels were fairly high when I was doing so. Or perhaps some builders don't have soldering equipment with grounded tips? It certainly is an enigma...
72 de Russ, va3rr
toggle quoted message
Show quoted text
On Thu, Jul 11, 2024 at 10:16 AM, Chuck AI7SY wrote: A possible solution could be as simple as antistatic bagging the main board
for shipping.
|
Doh! Indeed it is. What I was seeing was the prototyping board through the bubble wrap, now that I've got the thing completely unpacked. That rules out my shipping idea.
|
Re: My QMX+ has a .3 ohm short on VDD
Dear? Ludwig,
thanks for the links.?? I got them yesterday and used the information to try to log into the diagnostics...
I did get the hardware page and some helpful information.?
thanks for passing them along.?? they are not easy to find without your links.
take care and have fun.
73 Dave WA5DJJ
|
Hello Chuck
The main board IS anti-static packed...?
Wolfgang Pauli once said to Niels Bohr after a lecture "Your idea is crazy, but is it crazy enough?".
My kit arrived Monday, and I've been finishing a 1.25m repeater before starting (think of a horse hanging their own carrot on a stick), but I opened the box to examine the packaging.
It would seem to be difficult to damage the chip once it's mounted on a board with ~1000 uf of bypassing. TI puts its usual 2 kV input static protection on this chip. So one has to work some to break the thing.
Hans, if you don't see such a problem with the QRP Labs assembly crew, I would posit that the issue could be static buildup inside the packaging, during shipping. Every little jostle rubbing the bubble wrap on the cardboard...
A possible solution could be as simple as antistatic bagging the main board for shipping.
|
Wolfgang Pauli once said to Niels Bohr after a lecture "Your idea is crazy, but is it crazy enough?".
My kit arrived Monday, and I've been finishing a 1.25m repeater before starting (think of a horse hanging their own carrot on a stick), but I opened the box to examine the packaging.
It would seem to be difficult to damage the chip once it's mounted on a board with ~1000 uf of bypassing. TI puts its usual 2 kV input static protection on this chip. So one has to work some to break the thing.
Hans, if you don't see such a problem with the QRP Labs assembly crew, I would posit that the issue could be static buildup inside the packaging, during shipping. Every little jostle rubbing the bubble wrap on the cardboard...
A possible solution could be as simple as antistatic bagging the main board for shipping.
|
Re: Another QMX+ got onto the air + Low Tx Output
Thanks Jim, let me know if you find anything...
73 Dave G4FAW?
|
Re: When 200 Hz is too wide
I believe the Audio filter is the one designed by Dave Cripe, NM0S, so you can get info on how to adjust the parameters from the documentation on this link:
--
73, Dan - W2DLC
|
Re: QMX+ audio amp/speakers
Randy, I don't know if it would be significant, but did you consider magnetic shielding? A steel jar lid might work.?
--
73, Dan? NM3A
|
TI actually has a white paper on failure rates on the documentation page for the chip, for those who would like to do a little casual reading. It's more generic for their manufacturing process and quality control, but it's an interesting read anyway.
--
73, Dan - W2DLC
|
Counterfeit is NOT a possible explanation. We order them directly from Texas Instruments.?
73 Hans G0UPL
Add me to the list that had to replace the 1804 .
I had never thought about counterfeit.? At least one aliexpress seller seems to think calling their's?
non-counterfeit is a selling point.
I guess there are a lot of counterfeit 1804's out there.
|
Add me to the list that had to replace the 1804 .
I had never thought about counterfeit.? At least one aliexpress seller seems to think calling their's?
non-counterfeit is a selling point.
I guess there are a lot of counterfeit 1804's out there.
|
Re: Issues with summer travel and hot cars?
Don statement is not? generally true for batteries.?
Between 35 C and 40 C there is a temperature that will trigger a massive slump in? Pb battery output (the? exact triggers for the voltage slump were not? know when I was doing O and G work) .? The big operators like Exxon Mobil and? Texaco will not allow? any sort of Pb battery to be used for critical? unctions on offshore platforms for this reason.? Consequently the poison of choice was? NiCad or? late NiMH battery packs.?
T
|
I'm waiting for my replacement PCM1804, too.
Hoping that it will solve the issue with my QMX.
I would agree to Andy. There seems to be an issue with this chip, but if you just take a look at the order backlog for the assembled devices and Hans comments about packing 1000+ kits, the defects are still in the permille range.
|
Chuck AI7SY
va3rr
Daniel Conklin
Timothy Fidler
Dirk