Date
1 - 10 of 10
QCX + 40m First Power Up Help,https://elektrotanya.com/cgi-bin/download2.cgi?dk=lwxopbs126ekuzaf3b6nxwxmvbs1m5yj6tjil3s3s3jzrrfw&fid=343959&file=ameritron_als-500m.pdf Snap Crackle Pop, Newbie #solution #supply #building #display #dummy
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Stephen Sherer <ke4ljh@...>
Ok,
The replacement reverse polarity diode has been installed. I have lights! Bias voltages ic 5-10 all check ok. Alignment completed. It's now time for the 12v initial power output check. After reading what information is available in the manual, how to use the internal power meter is still greek to me. Would you explain how to use the internal power meter and where it is hooked up? I also have an auto ranging DVM. -- KE4LJH Steve, Florida |
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Stephen Sherer <ke4ljh@...>
Ok Shane,
All of the IC's 5-10 checked out ok. Pins 8 and 4 are in this case VCC and GND. At this point, waiting for parts to arrive next week. -- KE4LJH Steve, Florida |
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Colin Weaving
Good afternoon Stephen.
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To give myself the best chance of avoiding first time power up issue there are 2 considerations. First, the Power Supply should only have enough current capacity to run the equipment. Any more than that, particularly many times more is inviting serious destructive consequences. Second, the unit to be powered up should be checked to ensure that any power lines are not shorted or close to ground, which would draw excessive current. So before applying power, I would check the resistance from the +12V input to ground. Mine reads 70Kohm ( multimeter red lead to +12v and black lead to ground ). This will check the +12V line on the board. Then check IC 11 pin 3 ( 5V output ) to ground, thus ensuring 5V line OK. I am not sure of the resistance as mine is boxed up, but anything approaching 200 ohms would be a concern and probably a lot higher than that. Your suggestion of a Wallwart of suitable power is OK, but I would use a 9V battery. Monitor the voltage on start up and be aware of a dramatic drop. Stop ! Some drop is to be expected and perhaps more with a Wallwart which are likely to have rather ambitious claims! You now have a situation that should avoid catastrophic consequences when you apply power. By that I mean smoke, burnt etch, blown components etc Once passed this (Smoke) test a more permanent power supply should be used. A suitably rated Wallwart could be used, however the variable quality of these may mean too much RF hash for best operation. As an aside, a variable current limited power supply, addresses the problem. Historically they have only been available on top of the linepower supplies, let’s say expensive . My bench supply for general work is rated at 3 amps, much more than generally needed so I have built a current limiter that has various steps starting at 100mamps. I tend to current limit even when equipment is up and running. It is so easy to short out components and particularly pins on closely packed boards. However there is now a Chinese PS on eBay for about £20 say $25 which has variable current limiting. So , I have ordered one, with not high expectations, but it just might be very useful. 73 Colin On 25 Nov 2020, at 12:52, Shane Justice <justshane@...> wrote:
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Shane Justice <justshane@...>
Hi Stephen I am on travel at the moment, so I'll be brief. When I speak of the circuit when making voltage checks of "the component", in this specific instance I am referring to the power nd ground pins of the op amp ICs. If you do not see the pins called out on the schematic for power and ground, you can determine the power and ground pin by looking up the part number on Google - look for a data sheet in pdf and look for the pin assignment for VCC and ground. On most ICs this would be pins 8 and 4, respectively by convention, but some analog ICs can have different pins for power and ground, hence why I suggest you look up the part's data sheet to confirm. This is generally a good step to confirm these pins are not shorted to something other than power or ground, respectively, prior to first application of power, so you reduce the likelihood of having wire insulation melting, or parts or traces emitting smoke. These sorts of events are what preliminary resistance checks are supposed to avoid. It can get expensive replacing components otherwise. If you can afford a power supply that has current limiting, I highly encourage you to invest in one, especially if you plan to build more kits and/or experiment with creating your own electronic circuits. I use such a power supply. It is always good to make the first power up of a newly constructed circuit with the current limit set to a low current- in the case of the QCX+, about 200 milliamperes (mA), as that is roughly the expected idle current of the radio. Any current draw by the circuit that exceeds 200mA will cause the power supply to emit an alarm to inform you something is not right. If the current status below 200mA, then the power supply will continue to supply power at that level, making it safe to probe the circuit for voltages during checkout and or troubleshooting. I should be where I can more fully answer your questions this evening, so please let me know if you have additional questions. Hang in there-- circuit construction and checkout are skills that are developed over time. Be patient with yourself and your learning process. You are doing great and asking great questions. I am going to try to catch a few more winks now Best regards, Shane Thank you all for the comments. |
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Stephen Sherer <ke4ljh@...>
Thank you all for the comments.
To answer a few questions. Yes, I have a DVM Dan, Visual inspection for whiskers and other shorts has been done many times. Each time I start a new session I begin with yet another visual inspection before anything else. To include, Looking for solder bridges or component leads that are too long, bent, and touching. And yes, I seem to find a new piece of tiny waste solder each time. But I think I have all that taken care of. Shane, "Prior to applying any more power to the radio, checking each integrated circuit for proper connection to power pins and ground pins." Could you clarify in more detail here what you mean? I don't think you are saying to check each individual component. I interpret this to mean a group of components making up a circuit? Could you clarify specific points, A to B so to speak, that I should check for continuity for these circuits before power is applied that would make sense from a learned troubleshooting perspective? This way I learn to identify specific circuits as mentioned, and how to check them for continuity to GND and positive voltage. I have looked several times at the troubleshooting video. However, these system checks in the video all seem to be AFTER power is applied. I actually planned to go through all the troubleshooting steps after startup as a matter of course, just to go through the process. Mike, Your comments about the power supply with limiting amperage visited me. When I applied power, the wires to the power supply "melted" just like a fuse! So yes, there was a little too much amperage involved.... Thanks for mentioning the 9v battery and a dummy load. I made up a dummy load from a 51 ohm, by the DVM, 5-watt resistor soldered inside the barrel of a PL259 then adapted the PL259 to the BNC connector. This particular PL259 came with a red dust cap on the barrel of the connector, so the dust cap goes back on to cover the barrel and keep debris out. This way I have a small portable field dummy load that stays with the transceiver marked with a red dust cap. Looks good too. Colin, Thanks for clearing up the power requirements, 120 milliamps or so on receive and about 500 milliamps on transmit. While I am waiting for the parts to arrive, If you could provide a little more detail on what points to check for continuity in the circuits before more power is applied. With this in mind, Is there a reason a one amp or less WALL-WART, at first 9v and later 12v should not be used for power? I have saved many of these over the years. I have a drawer full of them. I did save them for something? I think... I am learning a great deal already.... As Hans mentioned, it is a great learning process. Ordering: new Diodes for protection circuit today. Correct 2.1mm power plug. 9v battery for powering up at low voltage with current limit. Thanks for this one! Four Stereo plugs. A few 140-43 toroids: first, for a 1:1 choke and then a 49:1 transformer for a half-wave wire antenna for when there is room. I'll also be building a quarter-wave verticle wire with a telescoping fiberglass pole. I chose the 140 size toroid because I also purchased the 50w amp kit and will be installing this inside the enclosure. Hans mentioned I would be able to turn the amplifier on and off through the menu system for QRP or QRO along with a 20v regulator for the amplifier so the amplifier only receives 20v for the full 50w output. How, is yet to be determined. The tranciever itself will run on 12v. Should a single 140-43 size toroid be sufficient for 100 Watts or should I double up on the toroids to handle the power without saturation of the toroids when the SWR is less than optimal? I mention this as I plan to build a separate trans match, possibly a Z-Match for field use in the future. I mention my plans for the amp and antennas so that each of you may see the road ahead of where I am taking this project in the event you might have more comments to make as I progress through the build. Maybe this project will help me pass the EXTRA exam. That's right, after 26 years still just a general. Thanks to all of you. -- KE4LJH Steve, Florida |
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Colin Weaving
As already suggested, it sounds as you have a short that needs to be resolved before applying power again.
You describe using a 30A power supply. This has the likelihood of doing an awful lot of damage if there are any constructional errors . It would be OK once the rig is up and running, but still severely overkill for what is required. The QCX only needs 120 mamps or so on receive and about 500 mamps on transmit. My initial start up would be with a 9V battery . The receive ( and the Tx ) will work perfectly well with specified voltage levels reduces appropriately. Once past the smoke test and hopefully assurance that the receiver is working, then increase power input to 12V, but from an appropriate rated power supply. I use a 3A supply but not critical. Before applying power attach a dummy load or solder 50 ohm ( 47ohm ok ) from antenna output to ground. Just in case. Colin M3WCK |
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mike.carden
Unless the 20A power supply is one with a variable current limit that you can set to something like 500mA, it's a very bad idea to connect it directly to your QCX+ because any small mistake in kit construction will cause instant destruction of components. Initial power-on should be either with a current limited power supply at around 500mA or if that's not available, perhaps a 9V battery, and in all cases, with a 50ohm dummy load connected to the RF output. -- MC VK1MC |
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Shane Justice <justshane@...>
Stephen, Do you have an ohm meter /DVM? If not, that should be your first piece of test equipment. With a DVM you can check for continuity, shorts to ground, power, adjacent connections, etc. It's important to check each integrated circuit for proper connection to power pins and ground pins, prior to applying any more power to the radio. The suggestions to visually inspect the traces on the bottom of the board are a good rule of thumb, as well. A fat solder blob, or a thin whisker can short a pin or lead to an adjacent trace or connection and prevent proper operation. Take your time and do not rush the inspection process. Let us know how your inspection goes. Regards, Shane QCX+ first power up |
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I'd say yes, you have to replace that diode. However, you definitely have a short somewhere, and it may not just be in the power input line. Look for solder bridges or component leads that are too long, bent and touching before you do anything else.
-- 73, Dan - W2DLC |
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Stephen Sherer <ke4ljh@...>
QCX+ first power up
Long story short: Diode 1N5818. Revers polarity Diode check, forward voltage 0.156v. Spec sheet indicates forward voltage should be 0.556v or so. First Power -Up: Arc at + pad JP27, No Blue screen on LED module. No power up with what I thought was the correct power plug. Fat plug with a large hole in the center. What happend: did not have correct power plug to connect 12v.dc. used jumper wires from 20 amp power Supply. + lead to +12v pad next to power connecter and label JP27. Negative lead to - GND pad at same location. Result: a 12v arc, when positive lead touched the + pad at JP2 No smoke. Diode D3, revers polarity protection now reads 0.156v forward drop. Visual inspection: no burned R, or C components. All components look ok. Do I understand correctly, D3 needs to be replaced? What else should be checked before next power-up. What meaningful checks can be done without power? Continuity checks performed: From +12v pad at JP27 To: R48 on front pcb, +12v pad at DVM/PWR just forward of R18, all good. Is the voltage regulator L7805 now suspect? Can it be checked without removing from pcb? Gentlemen, I would be very greatful for any thaughts, thinking and ideas you may have on how I should proceed. At this point I know so little I don't want to cause more damage which is what will happen without your help. -- KE4LJH Steve, Florida |
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