|
Well, I thought my holiday QMX+ build was deaf for week while my daughter occupied the guest bedroom with my shack in it. ?But the problem was me using a short whip without a counterpoise. ?I ran the QMX+ ?head to head against my other radio on a mag loop yesterday and heard the ft8 chorus loud and clear from 10m down to 40m. ?So definitely not deaf.
?
But there is a problem. ?If I repeatedly power cycle the QMX+ it sometimes starts quiet and sometimes starts painfully noisy. ?About 3/4tr starts are normal, 1/8th quiet, and 1/8th noisy. ?All the diagnostics look reasonable. ?I’d like to see if the usb audio stream has the same response, but I’m guessing that I need a new pcm1804.
?
Any other ideas?
?
— rec —
|
Maybe connect the longest wire you have as an antenna, start on maybe 28 MHz and work your way down the spectrum. If you have a manual tuner, peak the noise on receive.?
operating with a tiny loop can be like looking through a tiny soda straw. Get some more data on receive.?
curt
?
?
|
Curt --
Good idea, I pulled some wire antennas out of storage, I'll give them a try.
Thanks,
-- 73 -- rec --
Maybe connect the longest wire you have as an antenna, start on maybe 28 MHz and work your way down the spectrum. If you have a manual tuner, peak the noise on receive.?
operating with a tiny loop can be like looking through a tiny soda straw. Get some more data on receive.?
curt
?
?
|
My HB QMX is painfully noisy when I start it. This issue is temperature sensitive in my case. I can put the radio near a room heat vent and the time it takes to settle down is significantly shorter. My shack is ~ 60 F in the winter. If I allow the radio to sit away from the vent overnight it takes a minute plus to calm down and not be painfully noisy. I am sure this is an 1804 issue and it will be addressed when all the things needed to change it get here.?
If your radio finally calms down it might be the same issue ? ?
73
Dick
W4PID
|
Thanks, Dick, that was worth exploring.
I put my QMX+ on a dummy load, started it, and sprayed the PCM1804 with a can of Dust Off compressed air with a director tube on it.
The compressed air would induce a chuckling noise that got louder and lasted longer the longer the chip was sprayed.? The noise quickly decayed when the spray was removed.? When turning the radio off and on, there was a vestige of the chuckling noise each time the audio powered up, but the chuckling quickly decayed.??
None of these experiments produced either the loud noise or the quieted receiver that I originally reported.? The chuckling was easy to listen to at the audio gain level that I last used, the painfully loud noise is a full throated hiss that forces you to remove an ear bud.
The maximum temperature rating for the PCM1804 is -70C to 125C, the recommended temperature rating is -10C to 70C.? When I pulled out my IR thermometer gun, it read the PCM1804 temperature at 15C, and the longest spurt of compressed air I tried only lowered the temperature to 13C.? Turning the receiver on I was only able to raise the PCM1804 temperature to 17C.? I think I need a different thermometer, or maybe the effect I'm hearing is actually the result of temperature gradient stress.
However, when I put the receiver back on the magloop antenna, tuned it to 14074, and turned it on in CW mode, I got the painfully loud noise twice in about 20 trials and normal reception on the other trials, no quieted receiver.? Repeating the experiment in DIGI mode, no painfully loud noise or quieted receiver in 20 trials.??
Is it possible that the AGC works differently in CW and DIGI?? ?And maybe this painfully loud noise is an AGC artefact?? The loud noise is similar to the effect of turning the audio gain up until the audio goes into distortion, though I can't make myself push the gain too far.
An interesting hour, thanks for the suggestion,
-- 73 -- rec -- ad5dz --
On Tue, Jan 21, 2025 at 6:36?AM Richard Hattaway via <rhattaway= [email protected]> wrote: My HB QMX is painfully noisy when I start it. This issue is temperature sensitive in my case. I can put the radio near a room heat vent and the time it takes to settle down is significantly shorter. My shack is ~ 60 F in the winter. If I allow the radio to sit away from the vent overnight it takes a minute plus to calm down and not be painfully noisy. I am sure this is an 1804 issue and it will be addressed when all the things needed to change it get here.?
If your radio finally calms down it might be the same issue ? ?
73
Dick
W4PID
|
There is no AGC on DIGI, see page 62 of the operating manual: "AGC: ON/OFF parameter which enables the entire AGC system. The AGC system is only operational in CW mode. -Chuck Harris, WA3UQV On Tue, 21 Jan 2025 15:05:59 -0700 "Roger E Critchlow Jr" <rec@...> wrote: Thanks, Dick, that was worth exploring.
I put my QMX+ on a dummy load, started it, and sprayed the PCM1804
with a can of Dust Off compressed air with a director tube on it.
The compressed air would induce a chuckling noise that got louder and
lasted longer the longer the chip was sprayed. The noise quickly
decayed when the spray was removed. When turning the radio off and
on, there was a vestige of the chuckling noise each time the audio
powered up, but the chuckling quickly decayed.
None of these experiments produced either the loud noise or the
quieted receiver that I originally reported. The chuckling was easy
to listen to at the audio gain level that I last used, the painfully
loud noise is a full throated hiss that forces you to remove an ear
bud.
The maximum temperature rating for the PCM1804 is -70C to 125C, the
recommended temperature rating is -10C to 70C. When I pulled out my
IR thermometer gun, it read the PCM1804 temperature at 15C, and the
longest spurt of compressed air I tried only lowered the temperature
to 13C. Turning the receiver on I was only able to raise the PCM1804
temperature to 17C. I think I need a different thermometer, or maybe
the effect I'm hearing is actually the result of temperature gradient
stress.
However, when I put the receiver back on the magloop antenna, tuned
it to 14074, and turned it on in CW mode, I got the painfully loud
noise twice in about 20 trials and normal reception on the other
trials, no quieted receiver. Repeating the experiment in DIGI mode,
no painfully loud noise or quieted receiver in 20 trials.
Is it possible that the AGC works differently in CW and DIGI? And
maybe this painfully loud noise is an AGC artefact? The loud noise
is similar to the effect of turning the audio gain up until the audio
goes into distortion, though I can't make myself push the gain too
far.
An interesting hour, thanks for the suggestion,
-- 73 -- rec -- ad5dz --
On Tue, Jan 21, 2025 at 6:36?AM Richard Hattaway via groups.io
<rhattaway= [email protected]> wrote:
My HB QMX is painfully noisy when I start it. This issue is
temperature sensitive in my case. I can put the radio near a room
heat vent and the time it takes to settle down is significantly
shorter. My shack is ~ 60 F in the winter. If I allow the radio to
sit away from the vent overnight it takes a minute plus to calm
down and not be painfully noisy. I am sure this is an 1804 issue
and it will be addressed when all the things needed to change it
get here.
If your radio finally calms down it might be the same issue ?
73
Dick
W4PID
|
All right.? Continuing to explore the subtleties of my new QMX+.
Starting my QMX+ in CW mode sometimes comes up very noisy, sometimes very quiet, but usually just right.??
Starting in DIGI mode always comes up just right.
That suggests that it's the AGC that's making things very noisy and very quiet.? (I'm doing all of this with the default AGC parameters.)
Well, can I get very noisy just by switching between CW and DIGI?? No.? I tuned 7074kHz and switched between CW and DIGI until I got tired, and I never got the radio to switch into very noisy or very quiet.??
What happens?if I start noisy/quiet on?CW and switch to DIGI?? The?noisy/quiet persists and I get noisy/quiet on?DIGI.? And it stays noisy/quiet if I switch back to CW again.
That seems to let the AGC off the hook.??
Is anyone else seeing this?? Here are the scores for three trials I just did on 20m.? I'm recording the number of starts that were right (R), noisy (N), quiet (Q), or other (O).??I set the audio gain to a comfortable level before I start.? Noisy is too loud to listen to, quiet is too soft to hear well.? The AGC is using the default parameters.? I thought that FT8 made a good source of noise, but apparently dead air may work even better.? Use a speaker if you aren't sure how noisy it gets.
R / N / Q / O 10 / 2 / 2 / 0 20m 14074 19 / 1 / 2 / 0 20m 14074 15 / 5 / 2 / 1 20m 14084 quiet (O was an intermediate noisy R and N)
Thanks for reading,
-- 73 -- rec -- ad5dz --
There is no AGC on DIGI, see page 62 of the operating manual:
"AGC: ON/OFF parameter which enables the entire AGC system.? The AGC
system is only operational in CW mode.
-Chuck Harris, WA3UQV
On Tue, 21 Jan 2025 15:05:59 -0700 "Roger E Critchlow Jr" <rec@...>
wrote:
> Thanks, Dick, that was worth exploring.
>
> I put my QMX+ on a dummy load, started it, and sprayed the PCM1804
> with a can of Dust Off compressed air with a director tube on it.
>
> The compressed air would induce a chuckling noise that got louder and
> lasted longer the longer the chip was sprayed.? The noise quickly
> decayed when the spray was removed.? When turning the radio off and
> on, there was a vestige of the chuckling noise each time the audio
> powered up, but the chuckling quickly decayed.
>
> None of these experiments produced either the loud noise or the
> quieted receiver that I originally reported.? The chuckling was easy
> to listen to at the audio gain level that I last used, the painfully
> loud noise is a full throated hiss that forces you to remove an ear
> bud.
>
> The maximum temperature rating for the PCM1804 is -70C to 125C, the
> recommended temperature rating is -10C to 70C.? When I pulled out my
> IR thermometer gun, it read the PCM1804 temperature at 15C, and the
> longest spurt of compressed air I tried only lowered the temperature
> to 13C. Turning the receiver on I was only able to raise the PCM1804
> temperature to 17C.? I think I need a different thermometer, or maybe
> the effect I'm hearing is actually the result of temperature gradient
> stress.
>
> However, when I put the receiver back on the magloop antenna, tuned
> it to 14074, and turned it on in CW mode, I got the painfully loud
> noise twice in about 20 trials and normal reception on the other
> trials, no quieted receiver.? Repeating the experiment in DIGI mode,
> no painfully loud noise or quieted receiver in 20 trials.
>
> Is it possible that the AGC works differently in CW and DIGI?? ?And
> maybe this painfully loud noise is an AGC artefact?? The loud noise
> is similar to the effect of turning the audio gain up until the audio
> goes into distortion, though I can't make myself push the gain too
> far.
>
> An interesting hour, thanks for the suggestion,
>
> -- 73 -- rec -- ad5dz --
>
> On Tue, Jan 21, 2025 at 6:36?AM Richard Hattaway via
> <rhattaway= [email protected]> wrote:
>
> > My HB QMX is painfully noisy when I start it. This issue is
> > temperature sensitive in my case. I can put the radio near a room
> > heat vent and the time it takes to settle down is significantly
> > shorter. My shack is ~ 60 F in the winter. If I allow the radio to
> > sit away from the vent overnight it takes a minute plus to calm
> > down and not be painfully noisy. I am sure this is an 1804 issue
> > and it will be addressed when all the things needed to change it
> > get here.
> >
> > If your radio finally calms down it might be the same issue ?
> >
> > 73
> > Dick
> > W4PID
> >
> >
> >
>
>
>
>
>
|
A correction.? The radio can start very noisy or very quiet in DIGI mode too.? Just got it to do both today.
On Thu, Jan 23, 2025 at 5:01?PM Roger E Critchlow Jr < rec@...> wrote: All right.? Continuing to explore the subtleties of my new QMX+.
Starting my QMX+ in CW mode sometimes comes up very noisy, sometimes very quiet, but usually just right.??
Starting in DIGI mode always comes up just right.
That suggests that it's the AGC that's making things very noisy and very quiet.? (I'm doing all of this with the default AGC parameters.)
Well, can I get very noisy just by switching between CW and DIGI?? No.? I tuned 7074kHz and switched between CW and DIGI until I got tired, and I never got the radio to switch into very noisy or very quiet.??
What happens?if I start noisy/quiet on?CW and switch to DIGI?? The?noisy/quiet persists and I get noisy/quiet on?DIGI.? And it stays noisy/quiet if I switch back to CW again.
That seems to let the AGC off the hook.??
Is anyone else seeing this?? Here are the scores for three trials I just did on 20m.? I'm recording the number of starts that were right (R), noisy (N), quiet (Q), or other (O).??I set the audio gain to a comfortable level before I start.? Noisy is too loud to listen to, quiet is too soft to hear well.? The AGC is using the default parameters.? I thought that FT8 made a good source of noise, but apparently dead air may work even better.? Use a speaker if you aren't sure how noisy it gets.
R / N / Q / O 10 / 2 / 2 / 0 20m 14074 19 / 1 / 2 / 0 20m 14074 15 / 5 / 2 / 1 20m 14084 quiet (O was an intermediate noisy R and N)
Thanks for reading,
-- 73 -- rec -- ad5dz --
There is no AGC on DIGI, see page 62 of the operating manual:
"AGC: ON/OFF parameter which enables the entire AGC system.? The AGC
system is only operational in CW mode.
-Chuck Harris, WA3UQV
On Tue, 21 Jan 2025 15:05:59 -0700 "Roger E Critchlow Jr" <rec@...>
wrote:
> Thanks, Dick, that was worth exploring.
>
> I put my QMX+ on a dummy load, started it, and sprayed the PCM1804
> with a can of Dust Off compressed air with a director tube on it.
>
> The compressed air would induce a chuckling noise that got louder and
> lasted longer the longer the chip was sprayed.? The noise quickly
> decayed when the spray was removed.? When turning the radio off and
> on, there was a vestige of the chuckling noise each time the audio
> powered up, but the chuckling quickly decayed.
>
> None of these experiments produced either the loud noise or the
> quieted receiver that I originally reported.? The chuckling was easy
> to listen to at the audio gain level that I last used, the painfully
> loud noise is a full throated hiss that forces you to remove an ear
> bud.
>
> The maximum temperature rating for the PCM1804 is -70C to 125C, the
> recommended temperature rating is -10C to 70C.? When I pulled out my
> IR thermometer gun, it read the PCM1804 temperature at 15C, and the
> longest spurt of compressed air I tried only lowered the temperature
> to 13C. Turning the receiver on I was only able to raise the PCM1804
> temperature to 17C.? I think I need a different thermometer, or maybe
> the effect I'm hearing is actually the result of temperature gradient
> stress.
>
> However, when I put the receiver back on the magloop antenna, tuned
> it to 14074, and turned it on in CW mode, I got the painfully loud
> noise twice in about 20 trials and normal reception on the other
> trials, no quieted receiver.? Repeating the experiment in DIGI mode,
> no painfully loud noise or quieted receiver in 20 trials.
>
> Is it possible that the AGC works differently in CW and DIGI?? ?And
> maybe this painfully loud noise is an AGC artefact?? The loud noise
> is similar to the effect of turning the audio gain up until the audio
> goes into distortion, though I can't make myself push the gain too
> far.
>
> An interesting hour, thanks for the suggestion,
>
> -- 73 -- rec -- ad5dz --
>
> On Tue, Jan 21, 2025 at 6:36?AM Richard Hattaway via
> <rhattaway= [email protected]> wrote:
>
> > My HB QMX is painfully noisy when I start it. This issue is
> > temperature sensitive in my case. I can put the radio near a room
> > heat vent and the time it takes to settle down is significantly
> > shorter. My shack is ~ 60 F in the winter. If I allow the radio to
> > sit away from the vent overnight it takes a minute plus to calm
> > down and not be painfully noisy. I am sure this is an 1804 issue
> > and it will be addressed when all the things needed to change it
> > get here.
> >
> > If your radio finally calms down it might be the same issue ?
> >
> > 73
> > Dick
> > W4PID
> >
> >
> >
>
>
>
>
>
|
Continuing explorations of QMX+ starting "very loud" and "very quiet" on some occasions.
Above screen shot is for a not loud/not quiet start.? I'm now going to restart until I get a loud or quiet start and take a comparison screen shot.? Got a "very loud" start on the 13th retry. This screenshot looks very much like the?previous screenshot, which shows that the IQ being sent to my laptop is immune to the "very loud" signal that the QMX+ is putting out on the Ear jack.?
And this last screenshot is from a very quiet start, so quiet that it's nearly silent in?the speaker.? The IQ signal looks just like the normal and very loud examples above.
So the causes of the changes in gain are in the audio processing on the MPU, in the DAC IC401, the audio amps IC404, or the audio output jack.? Color me mystified.? The DAC and the audio amps have no gain controls, and the audio output jack has no gain.? Visual inspection found no problems and tapping with a pen triggered no audible effects.? I kept wanting to blame the AGC, so I finally went and just turned AGC off.? I got a "very loud" start almost immediately.
It's as if the audio gain is being initialized to a random location that mostly turns out to be right, but occasionally turns out to be too high or too low.? It might help to have a read out of the actual value of the audio gain to see if it's tracking the gain changes I'm hearing.
No help.? If it starts very loud, the audio gain returns the same AG0054; that it does on normal starts.
-- 73 -- rec -- ad5dz --
On Sat, Jan 25, 2025 at 4:01?PM Roger E Critchlow Jr < rec@...> wrote: A correction.? The radio can start very noisy or very quiet in DIGI mode too.? Just got it to do both today.
On Thu, Jan 23, 2025 at 5:01?PM Roger E Critchlow Jr < rec@...> wrote: All right.? Continuing to explore the subtleties of my new QMX+.
Starting my QMX+ in CW mode sometimes comes up very noisy, sometimes very quiet, but usually just right.??
Starting in DIGI mode always comes up just right.
That suggests that it's the AGC that's making things very noisy and very quiet.? (I'm doing all of this with the default AGC parameters.)
Well, can I get very noisy just by switching between CW and DIGI?? No.? I tuned 7074kHz and switched between CW and DIGI until I got tired, and I never got the radio to switch into very noisy or very quiet.??
What happens?if I start noisy/quiet on?CW and switch to DIGI?? The?noisy/quiet persists and I get noisy/quiet on?DIGI.? And it stays noisy/quiet if I switch back to CW again.
That seems to let the AGC off the hook.??
Is anyone else seeing this?? Here are the scores for three trials I just did on 20m.? I'm recording the number of starts that were right (R), noisy (N), quiet (Q), or other (O).??I set the audio gain to a comfortable level before I start.? Noisy is too loud to listen to, quiet is too soft to hear well.? The AGC is using the default parameters.? I thought that FT8 made a good source of noise, but apparently dead air may work even better.? Use a speaker if you aren't sure how noisy it gets.
R / N / Q / O 10 / 2 / 2 / 0 20m 14074 19 / 1 / 2 / 0 20m 14074 15 / 5 / 2 / 1 20m 14084 quiet (O was an intermediate noisy R and N)
Thanks for reading,
-- 73 -- rec -- ad5dz --
There is no AGC on DIGI, see page 62 of the operating manual:
"AGC: ON/OFF parameter which enables the entire AGC system.? The AGC
system is only operational in CW mode.
-Chuck Harris, WA3UQV
On Tue, 21 Jan 2025 15:05:59 -0700 "Roger E Critchlow Jr" <rec@...>
wrote:
> Thanks, Dick, that was worth exploring.
>
> I put my QMX+ on a dummy load, started it, and sprayed the PCM1804
> with a can of Dust Off compressed air with a director tube on it.
>
> The compressed air would induce a chuckling noise that got louder and
> lasted longer the longer the chip was sprayed.? The noise quickly
> decayed when the spray was removed.? When turning the radio off and
> on, there was a vestige of the chuckling noise each time the audio
> powered up, but the chuckling quickly decayed.
>
> None of these experiments produced either the loud noise or the
> quieted receiver that I originally reported.? The chuckling was easy
> to listen to at the audio gain level that I last used, the painfully
> loud noise is a full throated hiss that forces you to remove an ear
> bud.
>
> The maximum temperature rating for the PCM1804 is -70C to 125C, the
> recommended temperature rating is -10C to 70C.? When I pulled out my
> IR thermometer gun, it read the PCM1804 temperature at 15C, and the
> longest spurt of compressed air I tried only lowered the temperature
> to 13C. Turning the receiver on I was only able to raise the PCM1804
> temperature to 17C.? I think I need a different thermometer, or maybe
> the effect I'm hearing is actually the result of temperature gradient
> stress.
>
> However, when I put the receiver back on the magloop antenna, tuned
> it to 14074, and turned it on in CW mode, I got the painfully loud
> noise twice in about 20 trials and normal reception on the other
> trials, no quieted receiver.? Repeating the experiment in DIGI mode,
> no painfully loud noise or quieted receiver in 20 trials.
>
> Is it possible that the AGC works differently in CW and DIGI?? ?And
> maybe this painfully loud noise is an AGC artefact?? The loud noise
> is similar to the effect of turning the audio gain up until the audio
> goes into distortion, though I can't make myself push the gain too
> far.
>
> An interesting hour, thanks for the suggestion,
>
> -- 73 -- rec -- ad5dz --
>
> On Tue, Jan 21, 2025 at 6:36?AM Richard Hattaway via
> <rhattaway= [email protected]> wrote:
>
> > My HB QMX is painfully noisy when I start it. This issue is
> > temperature sensitive in my case. I can put the radio near a room
> > heat vent and the time it takes to settle down is significantly
> > shorter. My shack is ~ 60 F in the winter. If I allow the radio to
> > sit away from the vent overnight it takes a minute plus to calm
> > down and not be painfully noisy. I am sure this is an 1804 issue
> > and it will be addressed when all the things needed to change it
> > get here.
> >
> > If your radio finally calms down it might be the same issue ?
> >
> > 73
> > Dick
> > W4PID
> >
> >
> >
>
>
>
>
>
|
I would take a closer look at the A/D chip.
From the CS4334 data sheet:
The MCLK-to-LRCK frequency ratio is de-
tected automatically during the initialization
sequence by counting the number of MCLK transi-
tions during a single LRCK period. Internal divid-
ers are set to generate the proper clocks. Table 1
illustrates several standard audio sample rates and
the required MCLK and LRCK frequencies. Please
note there is no required phase relationship, but
MCLK, LRCK and SCLK must be synchronous.
If there is some disturbance to these signals during the first LRCK period during startup, the device could have the wrong internal dividers and produce incorrect output.
?
I venture to guess this is your problem.? Such disturbance could be caused by a bad connection, noise on the signals, something internally wrong in a bad CS4334, or by the firmware generating those signals.? Likely not the firmware, or we would all be having these same problems.
?
Stan KC7XE
|
Thanks, Stan,
I waved my magic soldering wand over the CS4334, but remelting the solder had no effect.? ?First two tries at starting up yesterday resulted in two different very loud noises.
So replacing the CS4334 will establish whether the timing glitch is in the chip or in the signals that the chip is receiving from the MPU.? I will give that a try.??
Digikey lists the CS4334 as obsolete.? They have ~200 in stock but do not plan to restock when those run out.? ?And I had to agree that my order is non-cancelable and non-returnable.? I couldn't find any CS4334 at Mouser, they have some CS4335, also flagged as end of life, but they use a different?serial format.
I would take a closer look at the A/D chip.
From the CS4334 data sheet:
The MCLK-to-LRCK frequency ratio is de-
tected automatically during the initialization
sequence by counting the number of MCLK transi-
tions during a single LRCK period. Internal divid-
ers are set to generate the proper clocks. Table 1
illustrates several standard audio sample rates and
the required MCLK and LRCK frequencies. Please
note there is no required phase relationship, but
MCLK, LRCK and SCLK must be synchronous.
If there is some disturbance to these signals during the first LRCK period during startup, the device could have the wrong internal dividers and produce incorrect output.
?
I venture to guess this is your problem.? Such disturbance could be caused by a bad connection, noise on the signals, something internally wrong in a bad CS4334, or by the firmware generating those signals.? Likely not the firmware, or we would all be having these same problems.
?
Stan KC7XE
|
Going to need some help here.? I'm replacing the IC401, the CS4334 DAC, because of intermittent bad audio output levels at startup.? But I need confirmation on the proper orientation of the chip.
The replacement CS4334s arrived and they're as illegibly marked as the one I'm replacing.? End of life because they can't find a replacement printer cartridge no doubt.
I thought I saw a bar on one end of the installed chip, but I didn't, pin one is actually marked with a dimple that I didn't discover until the chip was removed.
There does not appear to be any pin 1 marker for IC401 on the QMX+ silkscreen, nor any pin indications on the Gerbers graphic in the assembly manual.
But pin 1 is an I2C signal, pins 1 through 4 are all I2C or I2S signals.? Pins 5 through?8 are all audio out signals.? So I'm assuming that pin 1 is below the C in IC401 on the silkscreen.? So pins 1-4 go towards the MPU, while pins 5-8 go toward the matrix of Rs and Cs that lead to IC404, the audio output amplifier.
I removed IC401 with hot air after masking with?Kapton.? It flipped off the footprint when I pushed it with tweezers while testing for movement.??
It looked like there might have been a cold solder joint on the I2C_SCLK pin.? The chip leg left behind an imprint of itself in the solder left on the pad.? So a little more rework diligence on my part and I might have solved this a week ago.
Please offer any other evidence for the orientation of IC401 before I solder it in backwards.
-- 73 -- rec -- ad5dz --
|
Roger,
?
You have it figured out.
On my IC401, there's a shiny flat round dimple over pin 1.
?
When holding an SOIC package such as IC401 such that the print is right side up,
pin one should be in the lower left corner.? Counting from pin 1 counter-clockwise
around the chip to go from pin 1 to pin 8.? The schematic has pin 6 grounded, if
you look closely with a bit of magnification (or at least better eyes than mine)
you will see an obvious connection to the ground plane around it.
You can check this connection with an ohmmeter to one of the big round mounting holes,
which are also connected to ground.? Pin 7 has VCC,? there's a labled VCC pin at JP106
near the far end of the front panel that you can check connection to.
?
Try looking at the chip under whatever magnification you have with a very strong light.
Slowly turn the chip this way and that, at the proper angle the text on the chip (and the dimple)
should suddenly stand out.? The text is perhaps laser etched, not printed with ink which
could wear off.
?
Jerry, KE7Er
?
On Wed, Feb 19, 2025 at 03:00 PM, Roger E Critchlow Jr wrote:
Going to need some help here.? I'm replacing the IC401, the CS4334 DAC, because of intermittent bad audio output levels at startup.? But I need confirmation on the proper orientation of the chip.
|
The QMX+ assembly drawing shows the identifying print of IC401 in the standard orientation.
?
On Wed, Feb 19, 2025 at 04:06 PM, Jerry Gaffke wrote:
When holding an SOIC package such as IC401 such that the print is right side up,
pin one should be in the lower left corner.
|
Hi Roger,
I hope these photos will help.
?
Mel. M0KMD
?
|
Thank you, Jerry,?
It appears that this issue is fixed.? I just made 40 restarts with IC401 replaced and suffered no very loud or very quiet starts.
Thanks to everyone who chimed in on the problem.? Learned to look for the ground connection, and that chip labels have a standard orientation with respect to ground, and that Hans draws the silk labels in standard orientation, except when he doesn't (eg IC407) where he puts an explicit pin 1 marker instead,
And thanks to Mehmet for the excellent photo which does help cement everything.
Now to figure out why the QMX+ thinks my antenna is better than NanoVNA does.
-- 73 -- rec -- ad5dz --
Roger,
?
You have it figured out.
On my IC401, there's a shiny flat round dimple over pin 1.
?
When holding an SOIC package such as IC401 such that the print is right side up,
pin one should be in the lower left corner.? Counting from pin 1 counter-clockwise
around the chip to go from pin 1 to pin 8.? The schematic has pin 6 grounded, if
you look closely with a bit of magnification (or at least better eyes than mine)
you will see an obvious connection to the ground plane around it.
You can check this connection with an ohmmeter to one of the big round mounting holes,
which are also connected to ground.? Pin 7 has VCC,? there's a labled VCC pin at JP106
near the far end of the front panel that you can check connection to.
?
Try looking at the chip under whatever magnification you have with a very strong light.
Slowly turn the chip this way and that, at the proper angle the text on the chip (and the dimple)
should suddenly stand out.? The text is perhaps laser etched, not printed with ink which
could wear off.
?
Jerry, KE7Er
?
On Wed, Feb 19, 2025 at 03:00 PM, Roger E Critchlow Jr wrote:
Going to need some help here.? I'm replacing the IC401, the CS4334 DAC, because of intermittent bad audio output levels at startup.? But I need confirmation on the proper orientation of the chip.
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Richard Hattaway