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Whilst I'm waiting for my QMX+ to arrive I thought I'd try and fault find my QMX. I believe my problem stems from the multi-layer board and poor quality soldering iron.
So... I've got a new Hankko station. With the multi-layer pcb I think I've struggled to get enough heat into some of the joints.
Having spent a lot of time on the QCX+ QDX and QMX schematics and with the very informative posts here, I think I have a good idea of how everything works. One thing I'm missing is how TONE is generated on transmit. Is it generated in sdr and can the presence of keydown tone in the headphones indicate a workingPCM1804?
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Thanks.
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Phill EA5JHA
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The sidetone does not indicate a working PCM1804, which is only used when receiving.
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The sidetone is generated in firmware by the processor, which then sends the digital sound data
to IC401 (in the receiver section of the schematics) and on out to the headphones.
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When receiving, the processor gets digital data from the PCM1804, manipulates the data
using some rather fascinating algorithms, then sends the received signal out to IC401
as digital data and on out to the headphones.
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Jerry KE7ER
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On Sat, Nov 23, 2024 at 05:08 AM, Phill wrote:
Whilst I'm waiting for my QMX+ to arrive I thought I'd try and fault find my QMX. I believe my problem stems from the multi-layer board and poor quality soldering iron.
So... I've got a new Hankko station. With the multi-layer pcb I think I've struggled to get enough heat into some of the joints.
Having spent a lot of time on the QCX+ QDX and QMX schematics and with the very informative posts here, I think I have a good idea of how everything works. One thing I'm missing is how TONE is generated on transmit. Is it generated in sdr and can the presence of keydown tone in the headphones indicate a workingPCM1804?
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Thanks, Jerry. Looks like I need a better understanding of sdr.
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Phill EA5JHA
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Phil,
Something else to think about in a multilayer pc board is flux. ?Some solder doesn¡¯t contain enough flux to keep the solder runny enough through all the layers of a via or hole. ?So adding a very small drop of liquid flux in some of the holes before adding solder might make it flow better as the heat moves through to the deeper layers. ?
Experts in soldering might have other thoughts but I have read plenty of emails where adding a little flux as one is reheating a connections in troubleshooting solved the problem. ? Be the REASON someone smiles today.
Dave K8WPE
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On Nov 23, 2024, at 8:08?AM, Phill via groups.io <rocinante2021@...> wrote:
? Whilst I'm waiting for my QMX+ to arrive I thought I'd try and fault find my QMX. I believe my problem stems from the multi-layer board and poor quality soldering iron.
So... I've got a new Hankko station. With the multi-layer pcb I think I've struggled to get enough heat into some of the joints.
Having spent a lot of time on the QCX+ QDX and QMX schematics and with the very informative posts here, I think I have a good idea of how everything works. One thing I'm missing is how TONE is generated on transmit. Is it generated in sdr and can the presence of keydown tone in the headphones indicate a workingPCM1804?
?
Thanks.
?
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Phill EA5JHA
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On Sun, Nov 24, 2024 at 11:37 AM, David Wilcox K8WPE wrote:
I have read plenty of emails where adding a little flux as one is reheating a connections in troubleshooting solved the problem. ?
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A lot of folks try to add flux by adding more solder. This is the wrong approach, which is why I always keep a needle dispenser bottle of liquid flux at the ready.??
73, Don N2VGU
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Thanks, Dave, you've made me smile. I hadn't actually considered internal connections and I'm using 0.5mm solder which probably hasn't got enough flux for the job. I've got both liquid and paste flux so I'll try that next whilst I'm waiting.
Thanks, Hans, the QMX+ is in Istanbul so should be here this week.
Don, thank you, I'll try using a needle tip as I've some blunt ones for solder paste.
73
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Phill EA5JHA
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Phill,
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I agree that adding flux is a good idea when touching up joints.
But if I see solder flowing smoothly on the top or bottom board pad and also
over the component lead, I figure it's a good electrical connection.
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These boards have plated vias that make a solid connection to all copper planes, inner and outer.
Look closely at one of the plated through holes and you will see that the plating is a solid cylinder
going through the board that splays out to a flat disk on the top and bottom of the board.
That is all one piece of metal, a good solder connection to any part of it makes a good electrical connection.
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That said, having solder flow all the way through the board and spread out on the other side does
make the connection mechanically stronger, and a pad less likely to lift off the board if a part lead is tugged.
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Some parts can't deal with a lot of heat, so it's best to stop after you see the solder flow properly.
That's especially true of parts made of plastic like the connectors and encoders.
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Jerry, KE7ER
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On Sun, Nov 24, 2024 at 12:35 PM, Phill wrote:
Thanks, Dave, you've made me smile. I hadn't actually considered internal connections and I'm using 0.5mm solder which probably hasn't got enough flux for the job. I've got both liquid and paste flux so I'll try that next whilst I'm waiting.
Thanks, Hans, the QMX+ is in Istanbul so should be here this week.
Don, thank you, I'll try using a needle tip as I've some blunt ones for solder paste.
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Thanks Jerry, excellent advice. My QMX+ arrived today and I've already started with the build. I'm concerned about making good joints to the ground planes. I've done a couple of capacitors and I'm not happy with them. I'm using a Hakko 888D with a fine 0.5mm tip and extra flux. I can get the heat on the component lead but the pcb solder pad is really small. What temperature do you recommend to get a solid joint without frying everything.?
Kind regards
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Phill EA5JHA
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That Hakko claims to be 70 Watts, should be enough.? I'd go with a fairly thick tip for maximum heat transfer.? A flat at the end may also help in some cases.? I used this iron, set it to around 440C when building my QMX: ?
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Jerry, KE7ER
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On Tue, Nov 26, 2024 at 08:00 AM, Phill wrote:
Thanks Jerry, excellent advice. My QMX+ arrived today and I've already started with the build. I'm concerned about making good joints to the ground planes. I've done a couple of capacitors and I'm not happy with them. I'm using a Hakko 888D with a fine 0.5mm tip and extra flux. I can get the heat on the component lead but the pcb solder pad is really small. What temperature do you recommend to get a solid joint without frying everything.?
Kind regards
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On Tue, Nov 26, 2024 at 08:00 AM, Phill wrote:
with a fine 0.5mm tip
This is the problem.? Such a fine tip doesn't have enough thermal mass to heat the via. Use a larger tip.? Some like the medium chisel tips or flat-ended tips.? I used a medium normal conical tip.? ?The fine tips are great for replacing surface mount parts, but I didn't use a fine tip for any of the thru-hole soldering.? And I think when I did the metal BNC connector I used an even larger tip.
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Thank you both. I'll use a bigger bit and 440C and see how it goes.
I built the QMX and QDX with a similar iron to that one Jerry but perhaps I was just a little shy with the heat. I didn't like going over 420C. I'll experiment on the QMX first as it's a bit the worse for wear.
73?
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Phill EA5JHA
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I've successfully built several Q's. I use a 2mm conical tip on my WEP station at 400 C for just about everything. I have bumped the temp up to 480C to throw more heat quickly into large components like BNCs or other jack connectors.
I generally mentally count off about three to four seconds for most joints, after the solder is fully flowing into the leads and surrounding pads. Maybe a bit less for very fine pins.? I might drop down to a 1mm conical at 400 C for sneaking into tight spaces especially on the topside for adding a bit of solder on topside components, to help mechanically stabilize toroids leads for instance.??
I drop down to a very fine 0.5mm tip only for touching up individual IC pins or small SMD work.?
I use good 60/40 or 63/37 fluxed solder.? Mostly 0.31 diameter but occasionally 0.15 for really fine work. Kester makes outstanding products.?
And ChipQuik brand liquid flux as needed and their low-temp solder paste for certain SMD rework.
GREG
On Tue, Nov 26, 2024 at 11:00 AM, Phill via groups.io <rocinante2021@...> wrote: Thanks Jerry, excellent advice. My QMX+ arrived today and I've already started with the build. I'm concerned about making good joints to the ground planes. I've done a couple of capacitors and I'm not happy with them. I'm using a Hakko 888D with a fine 0.5mm tip and extra flux. I can get the heat on the component lead but the pcb solder pad is really small. What temperature do you recommend to get a solid joint without frying everything.?
Kind regards
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Phill EA5JHA
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I usually scrape magnet wire with a knife to make sure the enamel is off.
With the wire in the QMX+ kit, I am just poking it through the hole and soldering.
Hold for a few extra seconds while rubbing the tip of the iron around the base of the wire
to rough up any insulation that might still be there.
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I am often flipping the board over and setting it flat on the desk to work on the back.
The has it resting on any upright torroids, and those wires will eventually break.
I also ordered the dev board for the QMX, it comes with 4 nylon spacers and 8 nylon
screws for mounting the dev board.? I've installed these spacers and screws without
the dev board to hold it up off the desk.? Was necessary to also install the top screws
or there was zero clearance from desktop to the spacers, which makes me wonder
if people will have trouble when using the dev board.??
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All the surface mount parts on the board got auto-stuffed and then reflow soldered
using lead-free solder.? That solder will take much higher iron temperatures to melt
than the solder with lead that most of us use.? If I were to take off a part like the
PCM1804, I'd try to get some ChipQuik alloy in there with an iron at each pin
before torching the board with hot air, the ChipQuik melts at a very low temperature.
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On some parts it's best to clip the pins one by one with fine tipped diagonal cutters,
then remove the pins with an iron.? But with surface mount parts, that will rip the
pads off the board unless you do it just right.?
Best to practice on some old junk boards first.
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Jerry, KE7ER
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On Tue, Nov 26, 2024 at 09:50 AM, Greg McCain wrote:
I've successfully built several Q's. I use a 2mm conical tip on my WEP station at 400 C for just about everything. I have bumped the temp up to 480C to throw more heat quickly into large components like BNCs or other jack connectors.
?
I generally mentally count off about three to four seconds for most joints, after the solder is fully flowing into the leads and surrounding pads. Maybe a bit less for very fine pins.?
I might drop down to a 1mm conical at 400 C for sneaking into tight spaces especially on the topside for adding a bit of solder on topside components, to help mechanically stabilize toroids leads for instance.??
?
I drop down to a very fine 0.5mm tip only for touching up individual IC pins or small SMD work.?
?
I use good 60/40 or 63/37 fluxed solder.? Mostly 0.31 diameter but occasionally 0.15 for really fine work. Kester makes outstanding products.?
?
And ChipQuik brand liquid flux as needed and their low-temp solder paste for certain SMD rework.
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GREG
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As a general rule, if the solder isn't flowing you need to give it more heat.
No way around it.??
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Except for plastic parts like the connectors, it's astounding how much heat this stuff can take.
Hot air rework on large parts with lead free solder is way worse then what I do with my iron.
Don't tug at the part or you'll lift the pads off the board when removing a part.
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Jerry, KE7ER
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On Tue, Nov 26, 2024 at 09:28 AM, Phill wrote:
Thank you both. I'll use a bigger bit and 440C and see how it goes.
I built the QMX and QDX with a similar iron to that one Jerry but perhaps I was just a little shy with the heat. I didn't like going over 420C. I'll experiment on the QMX first as it's a bit the worse for wear.
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Correction:? There was zero clearance from the desktop to the torroids.
Adding the screws to the top of the spacers gave me much more confidence.
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Jerry, KE7ER
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On Tue, Nov 26, 2024 at 11:10 AM, Jerry Gaffke wrote:
I've installed these spacers and screws without
the dev board to hold it up off the desk.? Was necessary to also install the top screws
or there was zero clearance from desktop to the spacers, which makes me wonder
if people will have trouble when using the dev board.??
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Jerry and Greg. Thanks for the great advice. I'm going to put it to good use but first try increasing the heat on the old QMX board.?
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I'm surprised at how much heat the QMX+ needs. It must be nearly all ground plane!
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73
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Phill EA5JHA
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And.......Poof!
First time I've seen an inductor self destruct! L523 now a two-part component.
At least I know what it looks like inside.
Luckily, I can use one from the QMX.
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Phill EA5JHA
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Careful, if that went pop, you likely have a short somewhere.? It should only get small current in receive from the Vcc (5V), or 30mA in transmit from the tx bias current.? Maybe you have a 12V short to one of those...
Stan KC7XE
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Sorry for the confusion Stan. I'm still in the build phase. I don't think I put too much heat in to it, soldering. Just one of those things! Luckily I had a spare so clipped the old bits out and soldered a replacement across the leads.
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Phill EA5JHA
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Thank you, Guys. The QMX+ is finished!
Guess what? Same fault as the QMX. This isn't funny.
Everything works except transmit.?
I've checked the soldering of Q507 and continuity through L502. The LPFs all work on receive so that part of the circuit should be OK.
Diagnostic graphs are all OK except swr which I guess is due to zero output power.
Luckily a lot of fault finding data here so I'll start with testing the DAC input and R506? net and take it from there.
73
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Phill EA5JHA
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Phill
David Wilcox K8WPE
Donald S Brant Jr