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Re: RF power chain mods and improvements..
Mark McNabb
For sure,
SMD parts are not tolerant of PCB flexing.? Be sure when handling, mounting, placing in a vise, etc. that you you do not bow or twist the board in any way.? It should always be kept flat.? When in a vise, be especially careful of clamping hard end-to-end, as the board is being put under pressure to bow.? And when mounting in a box, make sure the case is flat and the stand-offs are all the same height.? Then be careful of plugging and unplugging connectors.? This is the one disadvantage of plastic housings -- some won't provide good support for the board. The advantage of SMD parts is compact size and short leads so there is little parasitic capacitance or inductance, but on the other hand one needs to be careful with the board.? It's vice-versa with leaded parts and boards! 73, Mark. |
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Re: RF power chain mods and improvements..
Those surface mount caps and resistors are easy to mechanically fracture.
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Flexing the board or excessive thermal gradients could do it. Pressing at it with meter probes can momentarily fix the fracture. Problems like this can often be found pushing at parts with a probe or maybe applying heat to specific parts, see if the problem comes and goes. I've had bypass 1206 caps short hard enough to burn a hole in the board at a nearby feedthrough.? No obvious damage looking at the cap under a microscope, but the manufacturer verified it was indeed an internal fracture.? Bleeding edge high capacity high voltage surface mount caps are especially delicate, maybe 47uF at 25v stuffed into a 1206. And their capacitance can be reduced to less than half the face value as the applied DC voltage rises from zero to the rated voltage. ?? ? Often, some rough rework with a soldering iron dislodges those metal caps on the ends from the stuff inside the ceramic, and the metal caps are hanging on by force of habit and a little bit of friction.?? This can also be very difficult to see by inspection. If I do rework and the surface mount parts looks the worse for wear, they get replaced. ? We've all dealt with cold solder joints. But with today's small parts and tight pin spacing, thin filaments of solder can also be an issue. They can be thinner than a human hair and maybe a millimeter long,? will give a dead short but are impossible to see without magnification. I've had this happen with good quality 63/47 tin/lead solder. None of this happens very often, in part because I am aware of the potential trouble and work to avoid it.? I find surface mount parts generally easier to work with than the through hole?equivalents. Assuming they are larger than 0402's, and pin pitch is better than 0.5mm. Jerry, KE7ER ? On Sun, Nov 25, 2018 at 10:47 AM, AndyH wrote:
Thanks for the confirmation, Allison. |
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Re: RF power chain mods and improvements..
Thanks for the confirmation, Allison.
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? ?When I removed (almost) all of the parts from the board for the pre-driver, I checked R961.? Since it measured the desired 2.2 ¦¸ I left it.? Everything else was replaced.? With the amp rebuilt, I had 13.5V in on that resistor and 10.2 on the other side.? I just swapped that 2.2 ¦¸ for a fresh resistor and the entire power chain is alive again.? I feel for the analog meter in the WM-2, but it was good to see it pegged again! ? I replaced every single part in the first three amps.???I wish I knew what happened.? I've never seen passives fail like that. ? ? Thanks for the hand-holding, ma'am.? Mission complete. ? ? Andy On Sun, Nov 25, 2018 at 11:26 AM, ajparent1/KB1GMX wrote:
AndyH, |
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Re: RF power chain mods and improvements..
AndyH,
Allison - is the 5V at the collectors reasonable?? If so, is it time to replace R92 and R95 with pots and adjust until it works? No.? NEarly all of the collectors from Q90 on are connected to the 12V bus (that is at 12V???) so unless the small value resistors re cooked that is just plain wrong.? Check R84 (10 ohms), R89 (2.2ohms), r961 (2.2 ohms). One end of each of those should 12v or higher and the other may be a few tenths less. Allison |
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Re: Help needed with KD8CEC memory manager
Woody
Rich,? FWIW - That is the error I received (using windows) after my Nano got fried.? Would connect, but data transfers failed.
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Good Luck! Woody ? KZ4AK On 11/24/2018 21:59, richard_a_morrisey via Groups.Io wrote:
Hello - I am also getting error receive length = 1/1027. I have tried almost every possible combination of firmware and MM. I was successful with 1.097beta over the summer, then tried the I2C meter. At one point I lost the ability to communicate via Memory Manager to EEPROM. I use linux ans I am able to upload .hex and use the IDE to read all EEPROM values. For Memory Manager I need to use wine. I've used it successfully in the past this way. I was able to calibrate and save settings etc. |
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Re: RF power chain mods and improvements..
These data are for the pre-driver.? 13.8V input.? Everything in the amp has been replaced except for R961, the 2R2 at the TX input.? When the amp was cleared to the bare board, R961 measured 2.2¦¸ so I left it.
I had zero bias until replacing C90, C91, and C92.? At that point, there was 2.5 mA at all four emitter resistors.? Then I replaced R90 and R93 (which are 100 ¦¸ but measured 94 ¦¸ actual when removed) with 100 ¦¸ 1% resistors - and bias dropped back to zero.? I replaced R90 and R93 and still no bias. There's no current at the 11¦¸ emitter resistors (R911, R96, R941, and R942).? There's 3 mA at R90 and R93.? There's 5V at the collectors of all four 2N2222As. Allison - is the 5V at the collectors reasonable?? If so, is it time to replace R92 and R95 with pots and adjust until it works? |
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Re: RF power chain mods and improvements..
This is still kicking my butt.? I have been completely rebuilding the stages from scratch.? All parts removed, traces checked, then all parts replaced with new.? Q90, the pre-driver, and the final stages are working.? The pre-driver Q911/Q912 are still running away as they rapidly heat.? They start at 20 mA of bias and the voltage increases across the 11 ¦¸ emitter resistors at a rate of about 1-2 mV per second.? I've removed, checked, and replaced all of the transformers multiple times.? 2N2222As replaced multiple times.? I've built multiple kits with SMD parts - flux, 60/40 solder, and 600¡ãF on the WES51 iron haven't let me down yet.? The pre-driver had zero bias after replacing everything except R90 and R93, and the three caps.? After replacing the three .01uF caps, I got 2 mA of bias.? After replacing R90 and R93, there's no change.? Signal is getting through the chain and relays - I can trace the signal through the stages to the antenna - it's just that the pre-driver's cutting the signal roughly in half.? This doesn't make any sense.
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Does any of this sound even remotely familiar??? On Mon, Nov 19, 2018 at 03:58 PM, ajparent1/KB1GMX wrote: On Sun, Nov 18, 2018 at 10:32 PM, AndyH wrote: |
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Re: Raduino help?
I found that C50, C51 in the AF preamp and C63 of the mic output were causing my issue with microphonics. I replaced those three with 1uf electrolytics. Never use ceramic coupling in audio.? On Sat, Nov 24, 2018, 6:33 PM <jk.futter@... wrote: There are quite a few microphonic components on the PCB |
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Re: To shield or not to shield, that is the question.
You can get copper EMI tape on ebay for much less than the cost of the spray. When you overlap the edges it is conductive from one piece to the next. Same stuff used in tv sets and monitors to provide shielding over some flat cables.
Harvey, WA2AAE |
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Re: Raduino help?
There are quite a few microphonic components on the PCB
in order of importance MLC chip capacitors with DC bias applied ie coupling "c"s All crystals whether used as frequeny souces (oscillators) or filtering Air wound coils Coils with cores where the coil is not fixed to the core material de ZL2XRF |
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Re: Help needed with KD8CEC memory manager
Mike Short
I have had the same error. ? Mike On Sat, Nov 24, 2018 at 3:59 PM richard_a_morrisey via Groups.Io <richard_a_morrisey=[email protected]> wrote: Hello - I am also getting error receive length = 1/1027. I have tried almost every possible combination of firmware and MM. I was successful with 1.097beta over the summer, then tried the I2C meter. At one point I lost the ability to communicate via Memory Manager to EEPROM. I use linux ans I am able to upload .hex and use the IDE to read all EEPROM values. For Memory Manager I need to use wine. I've used it successfully in the past this way. I was able to calibrate and save settings etc. |
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Re: To shield or not to shield, that is the question.
It must be metal. A basic of building good radio equipment. It keeps unwanted RF out and in.? Shielding is also a basic. Take a look inside any commercial transceiver and you will see it. Lay out is important too, keep inputs away from outputs. I have built uBitx into the case of an old Kenwwod TS120S and and it has worked out quite well. Roger ZL2RX |
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Re: CW operation uBitX
#ubitxcw
I just added another connector with the two resistors so I wouldn't have to adapt the cable of my paddle. Guess somehow it should be 'doable' to automate the detection key or paddle as the measured values on the pin are different. But with the latest GUI interface of Nextion and CEC firmware is pretty simple and quick to change the key/paddle. ? What I am hearing is the same tone as the CW tone but much fainter but I have my GP-5/SSB maybe 4 ft away from my uBitX. It is like some background noise when the key is not pressed and it seems to increase slightly in frequency before the uBitX returns to RX. My uBitX has been performing pretty well on FT8 so am not too worried about it. My setup was with an efhw antenna in the attic and reached about 6400 miles on 10m back in March with a measured output of about 2.6 Watts maximum.? Guess it was a typo about the AGC, I have the kit from Kees based on the ND6T design, also have the click-fix kit. 73s de John, K5GT ? |
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Re: Help needed with KD8CEC memory manager
Hello - I am also getting error receive length = 1/1027. I have tried almost every possible combination of firmware and MM. I was successful with 1.097beta over the summer, then tried the I2C meter. At one point I lost the ability to communicate via Memory Manager to EEPROM. I use linux ans I am able to upload .hex and use the IDE to read all EEPROM values. For Memory Manager I need to use wine. I've used it successfully in the past this way. I was able to calibrate and save settings etc.
Can someone please help guide me to the best solution. Thanks, Rich |
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Re: To shield or not to shield, that is the question.
Jack Purdum
Keep us informed! Jack, W8TEE
On Saturday, November 24, 2018, 2:08:31 PM EST, Gwen Patton <ardrhi@...> wrote:
I put a plastic case on my uBitX...but I sprayed the interior surfaces with several coats of a nickel-based RFI insulating spray. It's highly conductive, and I made sure to bond all the surfaces to one another. I do suggest that a thin clear coat be put over it, as the spray can leave some loose particles. Just put painters' tape over the surfaces that need to be exposed conductor for bonding purposes, and clear-coat just enough to keep particles from shaking loose onto the board. This is the spray I used:? I plan to do some playing with this stuff to see if one can spray an effective antenna conductor onto some sort of substrate. I'm going to try making a small transmitting loop using this stuff and a cardboard TV moving box. The box is in two parts that slide one inside the other, and am going to try using overlapping sprayed conductor surfaces to create a capacitor to tune the big loop, and put another small box with its own loop of conductor (maybe adhesive copper foil) to couple the rig to the loop. Since you can spray as wide a strip of this stuff as you want, it may be possible to get good efficiency and a wide bandwidth with it. We'll see. It's been my experience that the spray does work to help keep RFI at bay. Gwen NG3P |
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Re: To shield or not to shield, that is the question.
Mike Short
That¡¯s what foil is for On Sat, Nov 24, 2018 at 1:42 PM Joe Puma <kd2nfc@...> wrote:
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_Dave_ AD0B
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