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I think TLC272 should also do the job, except perhaps for the final headphone stage. It's a similarly specced part, and is available in DIP.
Regarding the supply voltage, look at the lowermost right corner. There you see (ok, it's an educated guess) all of opamps being supplied straight from 12V rail. Common sense tells that too, since the common mode voltage used in the circuit is 5V. Karlis |
You are correct: the TS922 is now only available in SMD packages. You
would either have to find some NOS DIPs or use an SOIC to DIP adapter. The other alternative is to find another suitable part. So far as I can tell, the QCX schematic doesn't show what the power supply voltage supplied to those ICs is, so I can't tell whether they are attached to the nominally 12V input or to the 5V regulated output. If it's the latter (which is suggested by the bias circuit seen on IC9) you could use a lower voltage op amp such as the TLV2462, which is the op amp that Adafruit sells to replace the TS922. It's a 2.7-6V op amp that otherwise has similar specifications and the same pinout. IC10 (the output amplifier) appears to be biased to run from the 12V rail so it definitely should NOT be replaced by a lower voltage part. On Sun, Sep 2, 2018 at 5:33 PM, John VA7JBE via Groups.Io <va7jbe@...> wrote: There's some great advice in this thread and replacing IC6-9 sounds like a |
Re: My first time QCX build - fail.
I've made progress but it still isn't working right. I rewired T1 and reinstalled it. That fixed the loud tone but I caused more problems. I lifted a trace off the board from pin 4 of T1. It appears to me to go to the source of Q5 so I hooked it directly to it. It now seems to work but I can't hear anything but noise and clicking when on an antenna. Also, now when I key the transmitter I can barely hear it in another receiver where before it was a strong signal. I'm close to giving up. I no longer have test equipment except a DMM.
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There's some great advice in this thread and replacing IC6-9 sounds like a worthwhile mod, but I'm having a bit of trouble sourcing the TS922 in a DIP8 package.? They seem to have been discontinued in favor of SMD packaging.? Does anyone know of a source for these or a substitute that's still in production? John VA7JBE |
Karl Schwab
Great job on this video again Juddie with that CW switch plunger.? I did the same with mine, but I made my own plunger mod similar to yours.? I am interested now, in your "tilt up" stand that I can see in your video shots.? Can you describe how you did that?? Thanking you in advance and 73, de Karl, KO8S
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??? I do not know if it helps, but I have encountered all sorts of resets ,frequency shift?and blocking LCD?with VFO signal generator transformed into TX WSPR in 28 and 14 Mhz. Now I'm feeding the three BS170 with two LM7805 in parallel and the rest with a single LM7805. I chose?two LM7805 with the same voltage (4.98V) at 0.5A for parallel mounting without equalizing resistors. The secret I think is in the multilayer 0,47microfarad capacitors connected briefly between the input and the?GND at each LM as recommended by the manufacturers. The LM7805 is better than any other 7805. Everything goes right now for days ?with these? three?LM sources powered by an?single ?ordinary SMPS?9V / 1.5A? wall type.?? Obviously there are also 2 pieces short-mounted of 1000micro / 10V for each LM and a heater . Best wishes! ?Daniel , 73? YO8SAK |
Re: QCX tuning
Hi Alan,
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Academic?? ALL failures are an opportunity to learn and make a product more robust. I am surprised no one has talked about bringing up the power in steps? Measuring things as we go up to full power. From where I look, this would give up real data to look at in the event of failure. Lots of fun :). John Concord, NH On Sun, 2 Sep 2018, Alan de G1FXB via Groups.Io wrote:
Hi Glenn, |
Re: QCX tuning
¿ªÔÆÌåÓýHi Glenn,I'm in defence of all Hans views as well.? /g/QRPLabs/message/26421 (I keep pointing out his statement that he has never experienced a failure of any prototypes and beyond to production testing. Last was my Post /g/QRPLabs/message/26498) What I'm trying to understand is the conditions that lead upto what appears to be a one or two a week report of PA failure, Is it always user abuse, and / or is there any easy solutions ?. My posts:- /g/QRPLabs/message/26420 ?/g/QRPLabs/message/25533 /g/QRPLabs/message/25822 Putting it into perspective the QCX has celebrated it's first birthday Best case, its perhaps 52 out of 5500 units built, equates to just over 1% failure(?) of the most heavily stressed and abused components of any transmitter. (it's probably fair to assume that failure is likely to be under rather than over reported, many would just replace the components rather than post a question about it here?) It's academic, we will move on and soon have a new unit to talk about.? :-) Alan On 02/09/2018 16:44, Glen Leinweber
wrote:
In defense of Hans, |
Re: My first time QCX build - fail.
Ted - I had a similar experience.? Be sure you are using a stereo plug in the key jack.? The QCX requires one.? If you put in a mono plug it just keys the transmitter, and the tone you hear may be the side tone.?
After my build I heard a tone, so I took my time to carefully do the alignment steps.? That ruined my finals because they were on transmit for so long,? To make sure, when you're doing alignment just unplug the key from the jack and use the little onboard key. I had to replace several transistors. That may not be your problem, but it is one to avoid. 72 and good luck Gary W0ITT ? |
Re: QCX tuning
In defense of Hans,
I don't recall seeing a brag about QCX able to handle infinite-SWR conditions. (ie: antenna short or open-circuit). ?I can see a dangerous scenario.... if you're using an open-circuit type outdoor antenna - one that measures open-circuit resistance between driven element and ground. An extreme example might be a kite-elevated long wire. This type of antenna can attain a considerable charge, and rise to very large DC voltage levels. Then you attach this antenna to your radio. Could even be an un-powered radio.... Ka-blooy! The QCX has an output filter that nearly floats as far as DC is concerned. It has a path through R43, a 120k resistor to one of the four 74ACT00 logic gates - most likely in a logic "high" state. If you measure the DC voltage at the antenna connection terminals with a high-Z DC voltmeter, you'll measure close to +5V. I would ensure that any antenna has a DC path to ground, either through a RF choke, or a resistor, to bleed off any static charge. The QCX's 120k resistor path is too feeble to serve as a reliable discharge. A charged antenna can blow the finals nearly instantly when connected. There is no over-voltage antenna protection in the QCX. A loop-type antenna is safer from this scenario, but I'd still include a discharge path from the loop to earth. |
Re: QSX radio feature requests
Hello Allison and Hans
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Many thanks for the detailed reply, I will take on board both yours and Hans' advice, much appreciated! Friday, August 24, 2018 On Fri, Aug 24, 2018 at 02:54 AM, Chris Wilson wrote: Think of this way would you intentionally put a choke in series with the three legs? I've used those driver ICs to 13.56mhz. More of same for wide traces and ground planes. Or from a different view point Hans did it right and it works to VHF. Allison _._,_._,_ -- 2E0ILY Best regards, Chris mailto:chris@... --
Best regards, Chris Wilson (2E0ILY) |
Re: #QCX 4174 Ready for practice test
#qcx
The practice test was negative. My mistake: My tuner tunes to antenna voltage, no control of adaptation to the PA. This caused the PA to overload, causing the MPS2907 to burn. Repair ok. Change tuner is in progress.
I use follow regulator https://www.ebay.de/itm/Mini-DC-DC-4V-12-24V-To-5V-3A-Adjustable-Step-Down-Power-Module-Buck-Converter/272694825804 In my overvoltage-protection the 0,47? - C is reduced to 10nF There is a unknown problem on my QCX: Full QSK works fine, Semi QSK not - no intermission between the characters (version 1.00e) 73 DL8LRZ |
Re: QCX tuning
It would be good to get to the bottom ofAlan, I don't know how Hans had no trouble although it could be that most QCX do survive abuse. Maybe only a few actually have problems? The design here was mentioned by someone, it shows how to protect 3 little BS170s from some class E hazards. Difficult to spot the actual PA components! 73 Alan G4ZFQ |
Re: QCX tuning
The LDG Z-100Plus requires only 0.1 watt to tune according to LDG and is rated for 125 watts which leads me to think that it has lower losses than some of the "QRP" tuners with much lower ratings.? Dunno for sure about that.? It uses latching relays so power consumption is almost zero once tuned.?
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No relation to the company...just a satisfied user.
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73,
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-Lee-??? WA3FIY
? ------ Original Message ------
From: "Richard Harris via Groups.Io" <g3otk@...>
Sent: 9/1/2018 2:07:18 PM
Subject: Re: [QRPLabs] QCX tuning
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Re: QCX tuning
Never a truer word said in jest,
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transistors being the fastest fuses on three legs..... Q1-3 & Q6 blown while protected by a F1A fuse, It does put things in perspective what a task it appears to be? It would be good to get to the bottom of what brings on the perfect storm while Hans testing didn't highlight anything. Alan On 01/09/2018 19:54, Alan G4ZFQ wrote:
It was a 1A fuse fast type. Supply voltage was at 15V via stepup converter fed from a 12V Pb akku.That might confirm the saying that semiconductors blow fast in order to protect fuses from blowing... |
Re: QCX tuning
>>>So, in the midst of this discussion, if my finals blow is there a ¡°drop in¡± replacement with similar characteristics but that will withstand considerably more abuse?<<<
No, a more robust device will reequire a stronger driver device and likely a? revised DC feed.? ?The class E has fairly narrow bounds before it gets to a bad state.?? To protect it use a switchable attenuator before the tuner 3 or 6DB is not all that much but?easily leaves enough power for a T1 to auto tune. The T1 tunes well even at 1W.? Or use a manual tuner?with a resistive bridge SWR detector (tayloe).?? Better suggestion, tune the antenna to not need the tuner.? IF a tuner is needed you not going from total mis-match to 1:1 All tuners will go through a state of high SWR to the radio, its unavoidable. Try it by hand and see. . Allison |
Re: QCX tuning
So, in the midst of this discussion, if my finals blow is there a ¡°drop in¡± replacement with similar characteristics but that will withstand considerably more abuse?
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72, Charles - NK8O On Sep 1, 2018, at 2:56 PM, Matthias Zwoch <zwoch@...> wrote: |
Re: QCX tuning
Matthias Zwoch
Am 01.09.2018 um 20:07 schrieb Richard Harris via Groups.Io:
Hi Matthias,Hi Richard, Thats a good idea. T1 should do it too with 3dB att - 2,5W. Using a 6db attenuator may cause the problem, that the tuner stops at a level what later is not good for the finals. I have a homemade Z-Match which does the same in the tune mode. But dont like the fiddling with the Z-Match. At my 40m QRP trx (Mrs. Mosquita) I had blown a driver transistor years ago also using the autotuner. The autotuner brought the driver stage to oscillate, the output got at abt 30W for a sceond (made for 5w) and the fuse was blown out. However the RD16HHF1 survived and only one transistor had to be changed. Made a modification in the driver stage and now I can tune Mrs. Mosquita even with a long tuning sequence with the T1. 73 Matthias, DD7NT |