Re: Computer not connecting to newly built QDX

#136705

I made it from parts from Amazon. The prototype printed circuit board is just a bunch of through-plated solder pads to mount and connect every type of USB receptacle. It is powered by a 5 volt wall adapter but a rechargeable cell could be used. All the receptacles are on break-out boards so the connections were easy.

--

73
Karl
KI4ZUQ

Re: [QMX] SMPS to linear regulator conversion tips

#136704

Signals ADC_5V and ADC_3V3 back to the host should be a bit high by maybe a tenth of a volt.

If the processor doesn't see a high enough voltage,? it waits until it does before running any further code.

It's ok if those signals are a bit high, but there is no margin on the low side.

?

I'm amazed the 78M33 works at all, that's a lot of power to dissipate.

I'd recommend either going with a bigger regulator (and a heat sink), or feeding the 78M33 from your 5v linear..

?

Jerry, KE7ER

?

On Tue, Jan 7, 2025 at 06:32 PM, Adam wrote:

Show quoted text

2. CPU needs two fake signals: ADC_5V (2.5 V) and ADC_3V3 (1.65 V). The
reason is that it still tries to drive nonexistent SMPSes, expecting
feedback on these two lines. It won't boot without them. Just provide
resistive dividers, like in the original design (resistor values are not
critical, I used 18k).

Re: Release of version 1.2 of ABS solution for QMX+ (Automatic internal antenna tuner, internal battery and internal speaker with audio amp) #ABS #ATU #PSU #QMXplus

#136703

Hi, Stan and Cal. Happy New Year. Please add me to the list for a full version. Just in case. Thanks 73 Ray ae5hn

Re: QMX and QDX - Not enough 5V PTT oomph

#136702

Donald, most MOSFETs have an internal diode, so the flywheel diode is not absolutely necessary for a small low-voltage relay.? If the relay has a large coil or runs off higher voltage, yes, I would definitely include the diode.

The very popular ATU100 tuner (7x7) has 14 relays with 14 FETs and just capacitors across the relay terminals, and I have not heard of any of those drivers blowing out (including in the one I have).

Stan

Re: The USB connection is not working.

#136701

Yup, never been able to use straight c to c... I think it's missing a resistor to tell the computer to just treat it like a basic USB device. Whenever I have used it on my USB c laptop I have had to use an OTG adapter and a USB c to USB a cable.

Re: QMX, one of op-amps self-oscillates at 25 MHz (or picks up the system clock?)

#136700

On Tue, Jan 7, 2025 at 06:48 PM, Adam wrote:

2. With one of BPF capacitors (C401, C402, C404) grounded on the IC402
side, buzzing stops (only hiss / static noise is present), of course the
capacitor that does this depends on the selected band. Probably because
grounding it removes the biasing done by R401 + R402.

3. Grounding these capacitors on the other side (RX_IN) does nothing, the
buzzing continues.

These two observations tell me that your problem is 'to the right' of the capacitor.? If it was 'to the left', i.e. towards schematic page 5, grounding the input side of the capacitor would also have made the problem go away.? If the buzz was coming through that capacitor, it could also be trapped on its input.? Grounding the selected one of those capacitors

Have you checked carefully R401/R402/C406? A bad C406 in that biasing circuit could cause oscillations and disturb the audio.

Are you certain that there is no anomaly with T401?? Maybe one of the trifilar windings partially shorting against another one, due to enamel being scratched?

Is the buzzing only on 'left' or 'right' audio, or both? If it is on both, it is unlikely that the source is the op amps, since past their inputs, the paths are independent.? If it is on only one, I would suspect that op amp.

And finally, as unlikely as it seems, IC407 has been the most common failure source of anything related to audio in the QMX.? If none of the previous apply, I would replace that one.

Stan KC7XE

btw - you are the third person now recently who I have heard blew the IC403 with a strong overvoltage burning through the 5V supply, myself being one of them (I inadvertently turned QMX+ on with a 17.5V supply).? I don't know why the nearly identical IC402 didn't also blow.? Maybe it's the doubled bias across the Z/W pins.

Re: QMX, one of op-amps self-oscillates at 25 MHz (or picks up the system clock?)

#136699

Chuck Harris via groups.io <cfharris@...> wrote:

On more than a few occasions I have found that a scope
probe will excite a high speed, high impedance op amp
circuit into oscillating.But sticking the probe didn't change anything in the audio. Wouldn't it do 
it, if this was the cause?

Anyway, an update, if someone's still interested.

After frying SMPS boards I decided to make linear regulators (which I 
generally wanted to do anyway) and I'm back to square one. QMX buzzes just 
like it did, but op-amp doesn't self-oscillate anymore.

5V line is clean too (with the SMPS it wasn't, there was some strange 
distorted waveform there, I can provide a photo if someone's interested; 
but the waveform is not there anymore and the symptom didn't go away, so 
it's probably irrelevant).

Some observations:

1. With IC403 removed the buzzing stops (it only hisses, normal radio 
static noise).

2. With one of BPF capacitors (C401, C402, C404) grounded on the IC402 
side, buzzing stops (only hiss / static noise is present), of course the 
capacitor that does this depends on the selected band. Probably because 
grounding it removes the biasing done by R401 + R402.

3. Grounding these capacitors on the other side (RX_IN) does nothing, the 
buzzing continues.

I ordered two new LM4562 amps, I want to blindly replace them and test, 
but it's just that -- blind waving of the soldering gun with no real idea 
what can be going on.

I have nine new 3253's (I had ten, but one replaced IC403 that developed a 
short after frying these SMPSes), but I don't want to replace IC402 just 
yet -- something tells me this chip is OK, I just see no reasons to 
suspect it, it's just a switch. Or are there reasons?

Further down the line we have Q508 and all these PIN diodes and filters. 
Frankly speaking, I don't see anything here that could cause this buzzing. 
Should I try removing Q508, even if grounding its source made no 
difference? This is so tiny and fragile that I don't want to remove 
components without any suspicion.

So, ideas are still welcome...

Thanks.

Re: Computer not connecting to newly built QDX

#136698

Karl,

Would you mind sharing the source of your tester(s)?

73!

de Bekir TA2RX

8 Oca 2025 ?ar 05:23 tarihinde Karl via <karlshumaker=[email protected]> ?unu yazd?:

Show quoted text

Here is my USB cable continuity tester:

--

That is the printer cable I am using for the QDX, IC-7300 and the QCU Clock.

All four LED's are lit so power and data functional.

73
Karl
KI4ZUQ

Re: QMX and QDX - Not enough 5V PTT oomph

#136697

On Tue, Jan 7, 2025 at 07:17 PM, Stan Dye wrote:

a better solution would be to add a FET switch to turn on your relay

Don't forget the flywheel diode across the relay coil so you don't blow out the driver.

There is also a current-limiting resistor behind the PTT output which could be reduced somewhat for more current, but a driver would be my choice.

73, Don N2VGU

Re: Soldering Station Recommendations

#136696

On Tue, Jan 7, 2025 at 06:25 PM, Dave S. wrote:

Solder: ?

I suggest Chipquik, Multicore or Kester 63-37 with RMA core solders vs Chinese mystery metal.? I use 0.020" and 0.032" a lot, 0.015" occasionally for real fine work.??

Also a couple pf pairs of #7SA (stainless, antimagnetic) tweezers.? you will want more than one, you will invariably drop them and they will invariably land light (pointy) end down, turning the tips to "elf shoes."

https://www.techni-tool.com/product/352TW011-7-SA-SE

Antimagnetic is important because many chip components have magnetic nickel electrode plating and some ICs have magnetic lead frame material.? Both will stick annoyingly to magnetic tweezers.

?

73, Don N2VGU

[QMX] SMPS to linear regulator conversion tips

#136695

Hi,

I just replaced SMPS boards in my QMX with a linear regulator board, and 
removed the power switch (I always found it annoying). Some tips, if 
someone wants to do the same:

1. 3V3 regulator (I used the 78M33 which was normally used to "bootstrap" 
the CPU before SMPSes took over) will get bloody hot. QMX draws around 100 
mA on this line, which isn't much, but at 12 V it translates to 870 mW of 
power dissipated in the regulator. Make sure you provide as much ground 
plane for heatsinking as possible. I did, and my regulator is still almost 
90°C. I'm not sure how it will behave long term.

2. CPU needs two fake signals: ADC_5V (2.5 V) and ADC_3V3 (1.65 V). The 
reason is that it still tries to drive nonexistent SMPSes, expecting 
feedback on these two lines. It won't boot without them. Just provide 
resistive dividers, like in the original design (resistor values are not 
critical, I used 18k).

3. Lines PWM_5V, PWM_3V3 and LIN_REG_EN can be ignored (unconnected).

4. 100 uF capacitors (instead of 470 uF ones used in original boards) seem 
to be sufficient. Maybe even smaller ones would be OK.

When it comes to the power switch removal:

1. V_IN can be hooked directly to +12V (but you lose reverse polarity 
protection this way).

2. PWR_HOLD signal can be ignored.

3. PWR_ON signal can be ignored, but the original SMPS board has a 100k 
pullup (to V_IN) on this line. Make sure your board contains this pullup 
as well (although I used a much lower value, 4k7). If you keep this line 
floating, then the (very sensitive) gate of Q202 will get triggered by 
literally anything.

4. QMX will power on automatically. When you want to turn it off by long 
pressing the knob, it will show "Shutdown!" and hang. At this stage, the 
MCU releases PWR_HOLD line, but without the power switch this does 
nothing. Only power cycle seems to be able to recover from this state 
(understandable).

5. CPU seems to save current state (mode, frequency) to EEPROM only upon 
shutdown, so if you just remove the power without shutting QMX down with 
the knob press, current state won't be retained. This can be a problem or 
an advantage.

Hope it helps.

Re: Computer not connecting to newly built QDX

#136694

Here is my USB cable continuity tester:

--

That is the printer cable I am using for the QDX, IC-7300 and the QCU Clock.

All four LED's are lit so power and data functional.

73
Karl
KI4ZUQ

Re: Computer not connecting to newly built QDX

#136693

In addition to what Lasse says, it may be necessary to "show hidden devices" in order to see the entry that is blocking you.

?

73, Mike KK7ER

?

Did that. Got this: "Unknown USB Device(Device Descriptor Request Failed)"

Got this about 8 times with all the attempts.

?

--

73
Karl
KI4ZUQ

Re: QMX and QDX - Not enough 5V PTT oomph

#136692

Thank you Stan?

Great suggestion!??

GREG

Show quoted text

On Tue, Jan 7, 2025 at 7:17 PM, Stan Dye via groups.io
<standye@...> wrote:

Greg, a better solution would be to add a FET switch to turn on your relay - the gate of a FET is what the output of QMX was designed for, not to directly drive a relay.

A simple FET switch and a 470nF capacitor across the relay terminals, with a 9V transistor battery (or 5V arduino power source) would work well to switch your relay.

Stan KC7XE

?

?

Re: The USB connection is not working.

#136691

An update, as always I think the problem is the simplest one, I have type-c to type-c cables, I couldn't get any response from any type-c port of the computer I was using, then I tried the type-a ports on my motherboard using a type-c to type-a converter, I could only get response from the usb2.0 usb port, it shows the device for 2-3 seconds, but then it keeps beeping as "unknown device", the solution is to buy a relatively older type-c to type-a cable and try the usb2.0 ports again, if not, try again on an older generation computer, try and try and try... I guess that's the fun of it :)

?

I'll write again with the latest situation, 73.

?

TA2KTK - Tayfun

Re: nothing happening

#136690

thanks Nick,

yes i have instakked ?the aux2 jumper.

measured also against the antenna plug earth withbthe same results.

but looking at the values do you think the 3.3v is ok?

?

hanz

Re: nothing happening

#136689

thanks Greg,

it is a difficult one.

yes i soldered the forced bootliader mode link.

hanz

Re: Soldering Station Recommendations

#136688

开云体育

I went this way and never have looked back: