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Hi Charles

It is usual situation when you have LPF winding not "configured". I have to play with squeezing or spreading toroids winding in LPF.

Moreover, it would be great if you attach LPF sweeps from terminal.

br, Yury

I changed the LPF settings and got improvement on 17 m ( now 4.0 w ) and small improvement on 17m.??

I will again try to do some tightening of turns on the toroid windings but component interference limits winding movement.

Any advice on that problem will be appreciated.

Charles
K5KXJ

Charles, is your power supply current limited? Is there a large voltage drop when you press T, maybe only for a moment? This could result in a software crash.

For low output problem please show LPF sweeps.

73 Ludwig

On Sat, Jun 1, 2024 at 03:57 PM, @Ludwig_DH8WN wrote:

For low output problem please show LPF sweeps.

Sorry, now I found the sweeps

Hi Charles,

sorry for the delayed answer. I was looking several times here for a post from you but found only now your PM. For a fast reaction it would be the best to send your posts here via groups.io.

When I'm right, two things are questionable:

1) Low output on one band. The most reason maybe the LPF. But a second maybe a decreased supply voltage. If the current will be higher and the power supply is current limited the voltage may drop a bit. This will result in a lower output. The reason maybe also a not good cable or plug. Because this I asked for your power supply.

2) You observed

An added observation: more than a very short press of T in terminal Diagnostics mode made it necessary to reset the radioby turning off/on the 12 v power supply.

This could be a result from a (partly) software crash. And this could result from a very short voltage drop, triggered by the raising current when sending (pressing T). (If the display backlight is on after the "crash" only the connection to the terminal emulation is broken but the controller is running. You currently used the diagnostics screen and because of this the controls are disabled. So you couldn't start the normal shut down).

So you should test the relevance of your power supply for 1) and / or 2).

I have an MFJ power supply that I can setto 12 vdc, but the current scale is not precise enough to indicate milliamps.

You should try this if the max current is more than around 1.5 A. In some special situation my QMX needs a bit more than 1 A. And if my power supply is limited to 1 A in this moments I went in a similar situation.

73, Ludwig

Ludwig,

Thank you for those insights into the workings of QMX and also the terminal app.
No problem on the "delayed answer" and thank you for the advice on responding
to "Group" rather than "Sender".? Your help is very valuable to my learning.

I will run the Diagnostics T press with the MFJ power supply, record power by band
and post results.

Charles
K5KXJ

Charles, it would be fine reporting also the current. Don't worry If not high accuracy. If available put a DMM (max current 2 A or higher) in the + line.

73 Ludwig

Ludwig,

I have done power supply testing you suggested.

Using my 30 amp MFJ p/s for 12 vdc to QMX I get the following:
1.? In Diagnostics terminal mode T press causes a roughly indicated 2.5 amp ( on
? ? ?the p/s's 0-32 amp scale ).? The p/s meter shows a steady 12 vdc ( 0-16 v scale )
2.? Without a terminal session running pressing the key causes the same indicated?
? ? current and voltage as in number 1.
3.? In both 1 & 2 the supply voltage on the QMX LCD drops from 12 to 11 v.

I am now trying to workout how I can use my DMM for a better measure of p/s
current draw on key down.

Thanks for your help with this.

Charles
K5KXJ

On Mon, Jun 3, 2024 at 08:42 PM, C R Murrell wrote:

a roughly indicated 2.5 amp

Charles, only 2 amp would be a lot more than normal (around 1 amp or less). Please take care when testing. Could you lower the voltage to 8 or 7 V? This would be not so dangerous for the QMX.

Please first check resistance from one drain of the PA transistors to GND (for DC all the four drains in parallel.) It should be some kiloohm or more. Only a few ohm means broken BS170.

If it's ok, I would remove the display from the mainboard (no enclosure) and test via the terminal. What is the current in RX mode?
Press T only for a few seconds and check temperature of the PA transistors. Take care when using your fingertip. It could be hot. If the transistors are really hot one or more could be broken. If not hot, repeat "T" for a few seconds two or three times more. If not hot after this, we have to search for an other reason for high current.

Do you have an oscilloscope? Don't worry if not, no problem.

73, Ludwig

HI Ludwig,

-Will lower supply voltage to 8 v for further testing.

- I previously measured 9.8 k ohms across BS170 drain to source.? Will recheck that measurement.

- Will do the temperature test as you describe and report.? The MFJ p/s reads about zero indicated
? but the scale is 0-32 amp.? Have not worked out an arrangement yet to use DMM for more precise measurement.
- i have an oscilloscope.

73, Charles

On Tue, Jun 4, 2024 at 05:34 AM, C R Murrell wrote:

- i have an oscilloscope.

Hi Charles,

use your oscilloscope, the probe set to 10:1 and good compensated, to check the signal at both connections T501 to BS170 and at one gate of BS170 at each group of BS170. Take care not to connect different solder points with your probe, danger for the QMX.
I hope bandwidth of the osci is much higher than the QMX frequency.
I checked my HB QMX with 8 V supply at 10 m. Here are the results to compare. If you use 20 m it should be similar.
1) Gate of BS170, same for each group


2) drain of BS170 - T501, same for each group


3) T501 secondary


73, Ludwig

On Wed, Jun 5, 2024 at 03:15 PM, C R Murrell wrote:

DMM mistakenly set to dc voltage not dc current.

Charles,
mistakenly setting DMM to voltage shouldn't burn a cable. Please check some documents (the internet) how to connect a DMM to measure current.

Don't know your DMM but using a DMM similar to you connect the "10 A" terminal to the positive from power supply and the "COM" terminal to the positive to the QMX. With the DMM switch set to "10 A" you should see the right values.

And take care. Commonly between the "10 A" terminal and the "COM" terminal you have a low resistance all the time, independent from the setting of the DMM switch. Some DMM are fuse protected. If you drove mistakenly to high current a fuse inside the DMM maybe blown.

73, Ludwig

Charles, the RX current is fine. The TX current is to high but not this much like assumed the last time.

Could you show please photos from your T501, one from each side with the holes?

I'm curious about the results from the oscilloscope.

73, Ludwig

Ludwig,

Please find photos below.? I included the underside of the board to show
solder joints.?

The T501 build on this project seemed to be easier than the RWTST I did
for my low band QMX Rev1 12 volt.

I will try to do oscope checks and report tomorrow.? Busy day today.

TNX and 73,
Charles

On Thu, Jun 6, 2024 at 03:41 PM, C R Murrell wrote:

The T501 build on this project seemed to be easier than the RWTST I did
for my low band QMX Rev1 12

Charles, I'm a bit confused. Do you made not a RWTST? But the QMX is for 12 V.

73 Ludwig