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QMX Capacitor Swap Gives Lower Power. #qmx

 

I just did the capacitor swap with C516 and C525 and they are installed as in the new build manual. Both 20M and 30M have lost power. 20M lost about 1/2 or a little less watt and 30M lost a full watt power using the Transmit test in the firmware 003. The other 3 bands are the same as they were before the work.

Both use LPF 2 so I suspect there is an issue with LPF2, but what? I just changed the capacitors and double verified they are in the correct locations, actually installed new ones, and rewound the L513 toroid that I removed to do the capacitor swap. All solder joints look good. Bad capacitor? Highly unlikely I would think.

Any and all ideas welcome.


73,
Cliff, AE5ZA
 

Cliff,
Check that the 'PIN' current in the settings is 30mA. My 20m setting was 5 and changing it to 30 upped the 20m power from 3.7 to 5.5 volts. (13 V input voltage)
--
73, Dan? NM3A
 

I think I broke all records putting my QMX on putty to change the 5 back to 30, but for my machine (#133) 20m stayed at 3.5 watts. All others are a steady 5 watts. Sandy KB3EOF
 

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Thanks for the reply Dan. I wish that was it, but it's already set to 30.

73,
Cliff, AE5ZA



On Jul 12, 2023, at 18:10, Daniel Walter via <nm3a@...> wrote:

Cliff,
Check that the 'PIN' current in the settings is 30mA. My 20m setting was 5 and changing it to 30 upped the 20m power from 3.7 to 5.5 volts. (13 V input voltage)
--
73, Dan? NM3A

 

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Hi Sandy,

I'm showing after the swap:

20M ? 30M ? 40M ? 60M ? 80M

2.7 ? 4.2 ? 3.8 ? 4.3 ? 4.7

It would be nice to have all the others at 5W, but not quite. I'd be happy with 4+ watts. 20 was 3 watts before the swap and 30 was 5 watts.

Raised the 12V in to 12.5 and they all went up a little, but that I would think would be normal.

73,
Cliff, AE5ZA



On Jul 12, 2023, at 18:48, Sandy <mac3iii@...> wrote:

I think I broke all records putting my QMX on putty to change the 5 back to 30, but for my machine (#133) 20m stayed at 3.5 watts. All others are a steady 5 watts. Sandy KB3EOF
 

Um....here's a bit about my results:

- BEFORE the swap 30M was putting out more than 1 watt higher power than 80M, 60M, and 40M ...? PLUS 20M was a 1/2 watt lower than 80M, 40M, and 60M. (And this with using the 5mA bias for 20M from a factory reset. The other bands were set to "30" for their "pin bias" btw.)

- AFTER the LPF cap swap 30M power was lowered and is at the same(-ish) power as the lower freq. bands BUT (alas) 20M went even lower than it had been and was now around? TWO full watts lower than the other bands !! ... So I upped the bias to "30" and got ONE of the TWO watts lost back.

End result, 30M is now at the same power level as 80M, 40M and 60M.... 20 is now even at a lower power level than before the swap. Nisht gut.

es vy 73 de "baab" w9ya

P.S...Software is now at XXX.003 and "factory resets" from BOTH the terminal and front panel.

P.P.S... NEW (and tested) caps were used for the "swap". C525 was mounted to the bottom of the board and is covered with blue tape to prevent shorts tot he case. I am assuming that this position is not the cause of the sad results outlined above.

P.P.P.S..... My next step will probably be to A) Verify power going into the LPF with an o-scope &/or B) verify the toroids and windings.


On Wed, Jul 12, 2023 at 04:48 PM, Sandy wrote:
I think I broke all records putting my QMX on putty to change the 5 back
to 30, but for my machine (#133) 20m stayed at 3.5 watts. All others are
a steady 5 watts. Sandy KB3EOF
 

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Bob,

Very similar to my experience. At present 30M is 1 watt lower than before and 20M about 1/2 watt lower. The only difference here is that both caps are installed in the normal manner on from the top of the board.

Please keep us up to date on how your testing goes. I'd love to improve things here or at least get back to where I was.

73,
Cliff, AE5ZA



On Jul 14, 2023, at 09:02, Bob Finch <w9ya@...> wrote:

Um....here's a bit about my results:

- BEFORE the swap 30M was putting out more than 1 watt higher power than 80M, 60M, and 40M ...? PLUS 20M was a 1/2 watt lower than 80M, 40M, and 60M. (And this with using the 5mA bias for 20M from a factory reset. The other bands were set to "30" for their "pin bias" btw.)

- AFTER the LPF cap swap 30M power was lowered and is at the same(-ish) power as the lower freq. bands BUT (alas) 20M went even lower than it had been and was now around? TWO full watts lower than the other bands !! ... So I upped the bias to "30" and got ONE of the TWO watts lost back.

End result, 30M is now at the same power level as 80M, 40M and 60M.... 20 is now even at a lower power level than before the swap. Nisht gut.

es vy 73 de "baab" w9ya

P.S...Software is now at XXX.003 and "factory resets" from BOTH the terminal and front panel.

P.P.S... NEW (and tested) caps were used for the "swap". C525 was mounted to the bottom of the board and is covered with blue tape to prevent shorts tot he case. I am assuming that this position is not the cause of the sad results outlined above.

P.P.P.S..... My next step will probably be to A) Verify power going into the LPF with an o-scope &/or B) verify the toroids and windings.

On Wed, Jul 12, 2023 at 04:48 PM, Sandy wrote:
I think I broke all records putting my QMX on putty to change the 5 back
to 30, but for my machine (#133) 20m stayed at 3.5 watts. All others are
a steady 5 watts. Sandy KB3EOF
 

And I had the opposite experience. My power went up with swapping the caps. Not sure what's different.?
--
73, Dan? NM3A
 

I also have better power output on 20 with the cap swap. I think your problem lies with the PIN diode bias. The band configuration screen that Hans showed for mod #2, shows only 5mA PIN bias on 20. That is wrong, it should be 30mA like all the other bands.
Gary
W9TD
 

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That's my big question. Did I use faulty parts? I don't think so, but no way to test the caps.

73,
Cliff, AE5ZA



On Jul 14, 2023, at 12:47, Daniel Walter via <nm3a@...> wrote:

And I had the opposite experience. My power went up with swapping the caps. Not sure what's different.?<IMG_2522.jpeg>
--
73, Dan? NM3A

 

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I wish it was that easy. Mine is already set at 30.

73,
Cliff, AE5ZA



On Jul 14, 2023, at 13:34, Gary W9TD <w9td@...> wrote:

I also have better power output on 20 with the cap swap. I think your problem lies with the PIN diode bias. The band configuration screen that Hans showed for mod #2, shows only 5mA PIN bias on 20. That is wrong, it should be 30mA like all the other bands.
Gary
W9TD

 

If you are referring to me....bias is at 30.....
 

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Yes, I was referring to your suggestion to check the forward bias setting.

73,
Cliff, AE5ZA



On Jul 14, 2023, at 16:18, Bob Finch <w9ya@...> wrote:

If you are referring to me....bias is at 30.....

 

That wasn't me....that was Gary, W9TD


On Fri, Jul 14, 2023 at 02:21 PM, Cliff wrote:
Yes, I was referring to your suggestion to check the forward bias setting.

73,
Cliff, AE5ZA



On Jul 14, 2023, at 16:18, Bob Finch <w9ya@...> wrote:

If you are referring to me....bias is at 30.....
 

Not the problem as both Cliff and myself have the bias set at 30...


On Fri, Jul 14, 2023 at 11:34 AM, Gary W9TD wrote:
I also have better power output on 20 with the cap swap. I think your problem lies with the PIN diode bias. The band configuration screen that Hans showed for mod #2, shows only 5mA PIN bias on 20. That is wrong, it should be 30mA like all the other bands.
Gary
W9TD
 

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Ops, sorry Bob. I'm watching too many threads.?

73,
Cliff, AE5ZA



On Jul 14, 2023, at 17:22, Bob Finch <w9ya@...> wrote:

Not the problem as both Cliff and myself have the bias set at 30...

On Fri, Jul 14, 2023 at 11:34 AM, Gary W9TD wrote:
I also have better power output on 20 with the cap swap. I think your problem lies with the PIN diode bias. The band configuration screen that Hans showed for mod #2, shows only 5mA PIN bias on 20. That is wrong, it should be 30mA like all the other bands.
Gary
W9TD

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