"PLL NOT LOCK PLEASE REBOOT"...  Davis Vantage Pro2 Weatherstation Repair - Page 1
Forum section: electronics / projects

author: hgg
author_rank: Frequent Contributor
timestamp: October 28, 2013, 08:53:09 am
content: Hello,I was wondering if someone can help me identify a problem I have with a wireless weather station boardthat stopped working. Its the Davis Vantage Pro2, a very nice wireless station with a lot of functionallity,until now...http://www.davisnet.com/weather/products/weather_product.asp?pnum=06162The PCB board is from the console that receives a data packet every 3 seconds from the wireless sensorstransmitter that is on the roof of the house. It stopped receiving data and gives the error message:PLL NOT LOCK PLEASE REBOOT.I have contacted Davis and they told me that :"There is a radio calibration process that occurs duringstartup. If the calibration process cannot complete itself it triggers the PLL error. Sometimes rebootingwill allow it to recalibrate properly and all is ok. Sometimes rebooting does not help and the console'sPCBA must be replaced. It appears we need to replace the board."Although they need to replace the board they will not do it because I live outside USA. They told me tocontact the local dealer in Greece, which I did and they could not help me as well even after contactingDavis themselves. That's what I call excellent customer support...Anyway, the wireless sensors transmitter works fine because I've tried another console and it works.The faulty console receives some data now and then. Maybe after two or three hours or so. So itworks intermittently so to say. I have included a hires photo of the board.Can you think what might be wrong with the board? Logic or passive component fault? I would saythat one of the CC1012 RF transceiver components might be faulty. Can you identify the blue chipon the bottom right corner of the board? What kind of chip is thatFinally can it be from a faulty crystal?So, where do we start the diagnosis of such an error?Any help is appreciated!Thanks.George.TOP of PCB Board:http://postimg.org/image/5wpng2qar/(click on the image again for a high resolution version.)Underside of PCB:http://postimg.org/image/onrkq8kv7/

author: hgg
author_rank: Frequent Contributor
timestamp: October 28, 2013, 11:13:00 am
content: Hi,Just installed the board back, powered it on and while it initially got some data packets, thenit stopped again. I probed the three crystals and while two of them oscillate according to theirspecifications the third crystal next to the transceiver chip does some strange things. It stopsand starts continuously. Generates a frequency for a while, then nothing and repeats itself.The other two look ok.The big one is 1.84Mhz next to the ATMEGA microcontroller and the smaller 32.768Khz next to it.1.84Mhz32.7KhzBelow is a video that shows the erratic behaviour of the Q-14.7-539 crystal and then it shows theother two as well.Is this normal for a crystal to behave like that? Doesn't it have a constant oscillation?

author: AndyC_772
author_rank: Super Contributor
timestamp: October 28, 2013, 11:52:48 am
content: Possibly not, when the extra capacitance of a scope probe is added to the oscillator circuit.

author: hgg
author_rank: Frequent Contributor
timestamp: October 28, 2013, 12:14:18 pm
content: Hi Andy,Did you reply to question "Is this normal for a crystal to behave like that?"or to the question "Doesn't it have a constant oscillation"I am probing ground and the pin of each crystal. The other two are perfectly stable.Do you think that the Q-14.7-539 crystal is the problem? The thing is I cannot findthat part number anywhere...Crystal

author: hgg
author_rank: Frequent Contributor
timestamp: October 28, 2013, 01:51:59 pm
content: There is definitely something going on with that crystal.I read in the datasheet of the CC1021 transceiver chip that through programmable configurationit has a crystal oscillator power up / power down capability. Does this mean that it can powerup or down the crystal itself or its internal frequency oscillation?The thing is that while all the other crystals have a 400-500mV, that one has zero Volts.CC1021 Datasheet:http://www.ti.com/lit/ds/swrs045c/swrs045c.pdf

author: AndyC_772
author_rank: Super Contributor
timestamp: October 28, 2013, 01:59:20 pm
content: I was replying to both questions - the answer is the same!The crystal is just one component of the complete oscillator circuit, and getting such circuits to oscillate at all can require some careful calculation, component choice and layout.Adding the extra capacitance of a scope probe to that system can easily destabilise it. It may stop oscillating, or shift slightly in frequency, or start and stop in an unpredictable way just like you've seen.That's not to say that the scope probe "is" the cause of the symptoms you're seeing, just that it could be. It could equally well be that the circuit is working exactly as intended, and that it gets powered on and off at various times by software, maybe as a power saving feature.

author: GK
author_rank: Super Contributor
timestamp: October 28, 2013, 02:38:30 pm
content: Crank the timebase sweep speed right down to the "roll" mode to see if there is a distinctive pattern to the on/off switching of the oscillation. If it's a faulty oscillator it will be unpredictable and random.

author: Anks
author_rank: Frequent Contributor
timestamp: October 28, 2013, 02:46:05 pm
content: You could also take the crystal out and make a circuit to test it. Bit brute force but it will remove the variables.

author: hgg
author_rank: Frequent Contributor
timestamp: October 28, 2013, 03:27:48 pm
content: QuoteOk, I see. Not so easy then...GK, I've just measured it in 'roll' mode and here is what I get:Wave1Wave2Wave3The thickess of the signal is because of some 50hz noise. I don't know how to remove that...I get mostly the first waveform, but sometimes the third and once the second. It has a mind of itsown...Generally speaking is it a good practice to switch on and off the crystal?Pippy, it is logical to assume that the sensor transmitter does not transmit packets continuously in orderto save power, especially because it works from solar power charging a supercapacitor. So if it doesnot send packets continuously and the base crystal switches on every 2 seconds for example, it will bevery difficult to get synchronized. Isn't that logical to assume?Anks, I might do that as well but its an smd component and I am not very familiar with solderingand desoldering them... If I do, whats an easy way to test the crystal? Can you just supply itwith a low voltage/current source?

author: hgg
author_rank: Frequent Contributor
timestamp: October 28, 2013, 03:36:09 pm
content: Ok, I tapped lightly the console on the table and got the following afterwards. (not during)Wave4I tapped it again and I got a smaller signal...Whats going on here?...

author: Anks
author_rank: Frequent Contributor
timestamp: October 28, 2013, 03:45:18 pm
content: There are loads of oscillator circuits on the internet just do a quick Google you could even buffer the signal so you probe doesn't interact with the crystal. Most older SBC would have such circuit with a watchdog attached that you got get a idea from.

author: hgg
author_rank: Frequent Contributor
timestamp: October 28, 2013, 06:28:36 pm
content: Anks I might use the Pierce oscillator if I finally remove the crystal. Thank you.Does anybody know what kind of chip is the following?(its on the right bottom side of the board)greenshot downloadIt goes through the board and below is its underside:UndersideI am no expert... but to me it looks some kind of EEPROM. Its too far from the micro controllerthough. I don't know. Could it be some type of diagnostic chip since its located near a JTAGlike connector? (You can also upgrade the firmware in that console. Could it be that it isstored in that chip?)If the calibration that the Davis technician mentioned is some kind of algorithm and the data havebeen corrupted, it could be beyond repair and I am wasting my time.I am still trying to think if its a component fault or a digital logic error.Any ideas?

author: Anks
author_rank: Frequent Contributor
timestamp: October 28, 2013, 06:39:07 pm
content: I'm no expert but looks like one of those temp and humidity sensors but I could be wrong.

author: G7PSK
author_rank: Super Contributor
timestamp: October 28, 2013, 06:44:08 pm
content: There is what looks like a red dipped tantalum capacitor its always worth checking those.

author: Anks
author_rank: Frequent Contributor
timestamp: October 28, 2013, 06:51:43 pm
content: On second look I'm willing to bet that some sort of UV detector.

author: SeanB
author_rank: Super Contributor
timestamp: October 28, 2013, 07:14:05 pm
content: Red dipped unit is a NTC thermistor. The ceramic board is a light sensor, probably used to measure daylight level and or cloud cover.

author: electronupdate
author_rank: Regular Contributor
timestamp: October 28, 2013, 07:59:48 pm
content: Since the FW is reporting a PLL lock error that would appear to be the logical starting point.The wireless communication's IC is from TI (CC1021). It states that the PLL lock status may be found at pin 9.As noted the wireless comm's is probably not active all the time to save power so you will need two channels on the scope.. one monitoring an enable , the other the status of the lock.Presuming that the lock signal does not occur, or is intermittent, it will be likely that the circuits associated with cc1021 should be looked at. As the #1 failure in most electronics is mechanical it would be good to scope the input antenna portion to make sure that's in good shape and then work inwards

author: hgg
author_rank: Frequent Contributor
timestamp: October 28, 2013, 08:32:03 pm
content: Indeed, I forgot that the console also measures inside temperature and humidity...SeanB the board is from the console that displays all the weather data and is inside thehouse, so the little blue chip doesn't look like to be a light/cloud sensor but even if it is ahumidity sensor why does it need to have 12 soldered pins!?!The little red part could be the temperature sensor.I applied some heat with a hair dryer... and its resistance went down from 10Kohm to 4Kohmand it was raising again as the unit cooled down. When the temperature reached again theinitial value, its resistance was exactly 10Kohms again.electronupdateI agree. The problem should be somewhere near the CC1021 chip.The problem is that when you power up the console the error message is the first think you find.Then you go into a menu that lets you choose which transmitting station to use and severalother parameters and when you go out of this mode, then you get the on/off signal from thecrystal. It also displays the letter R which in the manual it is stated that console waits tore-establish a connection.The Davis technician said that "there is a radio calibration process that occurs duringstartup. If the calibration process cannot complete itself it triggers the PLL error",so the error happens before any RF synchronization attempt is made!I've probed pin 9 on the chip and it has a2.99voltage. What does this mean?Locked or Unlocked? The chip works with 3V. Does this mean that the pin is high,and therefore actually PLL Locked?There is another small detail.. in the datasheet of CC1021."There is a finite possibility that the PLL self calibration will fail. The calibration routine in thesource code should include a loop so that the PLL is recalibrated until PLL lock is achieved ifthe PLL does not lock the first time. Refer to CC1021 Errata Note 002."Below is the Errata Note they are talking about: (Note 002)http://www.ti.com/lit/er/swrz007/swrz007.pdfMaybe someone can interpret the above information and suggest a testing method.It looks like that Davis did not do their homework, because more people are having the sameproblem.I still don't know where this "source code" mentioned above, is stored and how you can access it.

author: Alana
author_rank: Frequent Contributor
timestamp: October 28, 2013, 10:29:30 pm
content: Have you tried to visually check for bad solder joints and re-heat some that look suspicious?

author: hgg
author_rank: Frequent Contributor
timestamp: October 29, 2013, 05:30:51 am
content: Yes, that's the first thing I did. I looked at all the joints with a loupe and although theydon't have a lot of solder they look ok. I will check again just to be sure.From the datasheet:"An external clock signal or the internal crystal oscillator can be used as main frequency reference.An external clock signal should be connected be connected to XOSC_Q1 while XOSC_Q2 should beleft open....Using the internal crystal oscillator, the crystal must be connected between the XOSC_Q1 and XOSC_Q2pins. The oscillator is designed for parallel mode of operation of the crystal....The crystal oscillator is amplitude modulated. This means that a high current is required to initiatethe oscillations. When the amplitude builds up, the current is reduced to what is necessary to maintainapproximately 600 mVpp amplitude."Crystal Oscillator Circuit.XTALXOSC_Q2 ____.____|[]|____.____XOSC_Q1| |= C1 C2 =| |GND GNDThere is continuity between pin 1 of the crystal and XOSC_Q1 and between pin 2 and XOSC_Q1,so they have used the external crystal with the internal chip oscillator. In that way they canturn it on and off I think. They also mention that in order to initialize the oscillation high currentis required.Could it be that some part of the power supply rail has failed and cannot start the oscillation ofthe crystal connected to the CC1021 chip?

author: gman4925
author_rank: Regular Contributor
timestamp: October 29, 2013, 05:51:53 am
content: Quote from: hgg on October 28, 2013, 06:28:36 pmThat is the Barometric Pressure Sensor.Search Google for HP03S and you'll see similar ones.

author: hgg
author_rank: Frequent Contributor
timestamp: October 29, 2013, 06:11:59 am
content: You are right indeed! Its the barometric pressure sensor. Nice.I bet that it is the humidity sensor as well.

author: kayvee
author_rank: Regular Contributor
timestamp: October 29, 2013, 07:00:06 am
content: It's probably one of these from HOPERF.http://www.hoperf.com/sensor/barometer_16/

author: dr_p
author_rank: Frequent Contributor
timestamp: October 29, 2013, 08:08:19 am
content: Is the power rail OK? stable, no noise, etc.? Check at the bottom of the PCB, U11 looks like a linear regulator. Also, you might want to probe the big via between the DAVIS logo and 14.7 crystal. Shorted tantalum capacitors maybe?Any device added recently that might interfere with the radio communication? Have you tried using the indoor station closer to the outdoor one? Check the antenna for defects?

author: hgg
author_rank: Frequent Contributor
timestamp: October 29, 2013, 09:05:20 am
content: dr-p hello,QuoteNot sure about that. When I probe the circuit I always get a lot of 50hz noise. You can see thaton the oscilloscope signals I've posted. Only once or twice I had clean signals with no 50hz noise.Indeed U11 was the thing I checked first and it has 4.9V at the middle pin and 3.0V at the right one.The circuit draws around 5mA and 140mA with the backlight on. The voltage on C11 is stable when Iswitch on the backlight. Just a few uA drop.QuoteI don't understand. How do I do that?QuoteThere is no problem with RF interference. I've checked with a different console and it works ok.

author: alexig
author_rank: Contributor
timestamp: October 29, 2013, 09:43:47 am
content: Quote from: hgg on October 28, 2013, 08:32:03 pmThe datasheet says:9 LOCK Digital output PLL Lock indicator, active low. Output is asserted (low) when PLL is in lock. The pin can also be used as a general digital output, or as receive data output in synchronous NRZ/Manchester modeSo if it's high 3V then PLL is not locked which is what you are seeing. But check with a scope as it could change very quickly.With your scope, see if you can turn on low frequency reject in the trigger menu and see how you go with the 50Hz.When the power is off, check the tantalum caps with your multimeter by switching to ohms (make sure they are discharged already before doing so).

author: hgg
author_rank: Frequent Contributor
timestamp: October 29, 2013, 12:17:57 pm
content: Helloalexig,QuoteI missed that. So, PLL is not locked indeed.I probed pin 9 with the scope and it confirms the DMM measument.Pin 9 with DC coupling:Pin 9 DCPin 9 with AC coupling:Pin 9 ACHere a small 976mVpp oscillation is showing which looks similar with the signal of the crystal.By the way the LF Reject helped a lot here!Now for the capacitors.I've measured all the tantalum capacitors with the DMM in Ohms range and all of them wereshowing very high resistance in the MOhms range. So no capacitor is completely dead.When I measured them with the ESR meter though, I got the following results:C85 = 0.036RC76 = 0.036RC14 = 0.032RC21 = 0.029R andC11 = 0.124R... This is the one sitting next to U11 (voltage regulator?).All the capacitors apart C85 have a capacitance of 10uF. C11 has 4 times greater ESRthan the rest of them! Can this be an indication of a faulty cap? Maybe if not enoughcurrent can pass to the C1021 circuit it might not be able to start the crystal oscillationas stated in the datasheet.What do you think?

author: dr_p
author_rank: Frequent Contributor
timestamp: October 29, 2013, 02:30:27 pm
content: I dont't think it's a problem, but to be sure you can add a good 10uF on top of it.

author: hgg
author_rank: Frequent Contributor
timestamp: October 29, 2013, 06:27:02 pm
content: I've just tried a new 10uF on top of C11, but nothing happened.Same PLL error...There is a tiny tiny capacitor though labeled C28, that has a9 Ohms ESR!It measures exactly 3nF. Its right next to the crystal on the left side in the photo.Isn't that too high? Could it be that the 9 Ohms is a false reading?I have contacted Davis support with all the details and they've just replied to me saying that they do notrepair the faulty consoles. They just replace the boards. (I hate that habbit of the 21st century... )He also said that "sometimes it is the crystal Y51 (14.7) but it could be the radio chip or the CPU"Now, it does not seem likely to me that it is either the CPU or the radio chip. The weatherstation after the PLL error, works as usual and responds to every command and function.The PPL error is reported correctly as well. Its not a false positive.I have also asked him if they have taken into account Note 002 of the CC1021 Errata andprogrammed the firmware correctly in order to avoid PLL lock errors that are inherent tothe CC1021 chip! If he replies that they have, then the only thing that remains is to removethe crystal and test it.Don't you agree?

author: hgg
author_rank: Frequent Contributor
timestamp: October 29, 2013, 07:07:28 pm
content: Pippy,That is what I will do. Maybe its just the crystal after all.(Do you mean the tantalum ones or the tiny with the 9 Ohms ESR as well?)Thank you guys. You have been very helpful indeed!

author: SeanB
author_rank: Super Contributor
timestamp: October 29, 2013, 07:31:48 pm
content: If you do remove the crystal try resoldering it back the other way round. this may help, it does work in some cases with sluggish crystals.

author: hgg
author_rank: Frequent Contributor
timestamp: October 29, 2013, 07:45:43 pm
content: QuoteOk, I see. Thanks again!QuoteI will try that as well. If nothing happens I will test it on a Pierce oscillator circuit.

author: tsmith35
author_rank: Frequent Contributor
timestamp: October 30, 2013, 02:23:52 am
content: I opened up my Davis VP2 wireless remote transmitter and found a similar crystal in there. Peeled back the conformal coating to reveal:TXC G ("G" is very small)14.7 Ur03 (or UrOC)Might have a look athttp://www.txccrystal.com/crystal.htmlor call them for details. Here'sthe overview.Also, I read about another person who had the same problem. They removed the batteries and left the unit sitting for a long while, and the unit came back up fine when power was reapplied.

author: hgg
author_rank: Frequent Contributor
timestamp: October 30, 2013, 04:38:30 am
content: tsmith35 Hi,Thank you for the link.I think I have found the exact crystal on RS Electronics.http://uk.rs-online.com/web/p/crystal-units/6719264/?searchTerm=CAA-14.7456-18-3050-X&relevancy-data=636F3D3226696E3D4931384E4B6E6F776E41734D504E266C753D656E266D6D3D6D61746368616C6C7061727469616C26706D3D5E5B5C772D5C2E2F252C5D2B2426706F3D313326736E3D592673743D4D414E5F504152545F4E554D424552267573743D4341412D31342E373435362D31382D333035302D582677633D424F544826I am having the problem in the console, not the transmitter. The transmitter works fine.If I leave it for a long time with no batteries or power, then when it starts again it will receive somedata packets but then, it will display again the PLL NOT LOCK ERROR...So the faulty component whichever it is, has not died yet completely.I am waiting for a response from Davis just in case they have addressed the issue describedin the CC1021 errata, in a recent firmware. If they have, then I will remove the crystal to test it.My SMD skills are not the best, so I will wait...

author: tsmith35
author_rank: Frequent Contributor
timestamp: October 30, 2013, 06:14:12 am
content: Quote from: hgg on October 30, 2013, 04:38:30 amYeah, I know the issue you're having is in the console, but I figured Davis would use the same frequency for locking both...FWIW, any difference running on batteries vs wall wart?For that matter, are you running the latest (v3.12) version of the console firmware?

author: hgg
author_rank: Frequent Contributor
timestamp: October 30, 2013, 06:29:34 am
content: QuoteNo difference whatsoever.I am not running the latest firmware, that is why I've asked Davis is they have addresseda similar problem in their firmware updates. I am waiting for an answer.I cannot update the firmware now and check for myself, because I don't have the USB adapterwith me at the moment....

author: hgg
author_rank: Frequent Contributor
timestamp: October 30, 2013, 08:06:54 am
content: From what I see, to check if a crystal is working is not so straight forward.I will use the following Pierce oscillator (maybe the inverter oscillator is more simple) whichoutputs the main frequency of the crystal.Pierce OscillatorIt uses an N-Channel JFET but I don't have any and they are no so easy to find as well.My question is, can I use a MOSFET instead of the JFET? They both have a high input impedanceand the MOSFET even higher. But with higher input impedance you get a lower gain.Do you think that this substitution will work?I have some FQP30N06 lying around...

author: hgg
author_rank: Frequent Contributor
timestamp: November 02, 2013, 04:43:13 pm
content: Hi,I have just replaced the crystal and it does exactly the same thing!I have run out of ideas...Any suggestions? (apart throwing it in the trash...)

author: TrickyNekro
author_rank: Frequent Contributor
timestamp: November 04, 2013, 02:22:05 pm
content: The temperature and the humidity is measured by a small part at the left side of the microcontroller. I am not exactly sure about the code, the part is from Sensirior,probably a SHT11 or something similar. The "blue" chips seems to be an atmospheric pressure sensor. I´ve seen something like this from a Chinese company, can´tremember more though.The PLL not locking is probably happening because you have more jitter than allowable in your osc circuit. First thing I would check would be the power rails.Check all the possible power rails please, with your oscilloscope. Get the oscilloscope in AC mode and measure the maximum ripple. That would be a good start.Forgive me if something like that was said before, I´ve read most of the posts but I might have missed something.If you insist on throwing it away, I can accept the grand as well :-PBest Regards, LefterisGreece

author: tsmith35
author_rank: Frequent Contributor
timestamp: November 04, 2013, 05:46:36 pm
content: hgg, when did you buy the unit, and from what company/location? Perhaps I can pester Davis a bit...

author: hgg
author_rank: Frequent Contributor
timestamp: November 04, 2013, 06:22:33 pm
content: I was wondering what the little SHT chip was. Its on a tiny board place on the main board.I don't have any schematic diagrams, so I checked the ripple on all of the pins of the smd transistors/voltage regulators.The middle pin of the three of U11 : (178mVpp...) Supply voltage is 5V and the multimeterreads 4.3V now.U11Below the 3rd (right) pin of U11 : (Multimeter shows 2.999V steady. That goes to the CC1021)U11 3rd pinBoth the above were measured with AC coupling.I also get a very strange signal on the base pin of Q11. This time DC coupling was used.Q11 BaseDo you think there is a problem with the 5V rail? Can I check anything else?tsmith35very kind of you! I have it many years now, I cannot remember how many.It should be from 1996 because that is the date of the first weather data I can find in the PC.I remember that I bought it from the provantage.com company. I can search for the receipt.I might have it. What can you do though? They don't seem very cooperative...

author: TrickyNekro
author_rank: Frequent Contributor
timestamp: November 04, 2013, 06:39:02 pm
content: If I am correct U11 is the voltage regulator, or at least it looks like this, which also seems to be lineal since I can´t spot any inductors around(plus only 3 pins means no feedback pin so yeah).Replace every tantalum capacitor you see. If you can´t find tantalum caps around, use electrolytic caps but at least 10 times bigger in value.I see that most of the tantalums are 10uF, replace them with either the same, and if not possible in the immediate future use 100uF electrolytic.In parallel to the electrolytic caps use some 100nF ceramic also, that´s gonna help by a bit.But I think my friend that your problem is with the voltage rails. Replace the caps test the device and if it´s not ok then also replace the regulator.That´s all for the moment, I wait for your reply!!!Best Regards, LefterisGreece

author: hgg
author_rank: Frequent Contributor
timestamp: November 04, 2013, 07:08:55 pm
content: A lot of work!U11 is almost certainly the voltage regulator. It the only component that outputs 3V & 5Vat the same time.A small detail. When you switch on the unit it goes into a data entry mode first in order to inputsome info about your coordinates, units and from which transmitter it will receive its weatherdata. If you measure the 5V & 3V rails during that time, they are perfectly stable with 24mVripple max on the 5V supply rail. Crystals Y21 & Y22 are working normally and crystal Y51 is off.After that when you press ok it goes into its RF data acquisition mode and crystal Y51 starts andstops every two seconds approximately. That's when the 5V power rail has the large ripple andpulsing.5V are going into D12. (A large barrel diode) Then 4.3V are coming out of D12 and go into theC11 capacitor. All the other power rail points have either 3V or 4.3V after that.

author: TrickyNekro
author_rank: Frequent Contributor
timestamp: November 04, 2013, 07:17:22 pm
content: Can you power it from something like 7+ V let´s say? Please try that and report back, though I don´t feel like that´s the problem, still please do it,maybe it´s a part of it though.But yeah what you describe above is failed caps. The caps are bad so they can not handle the RF burst that is emitted?I have the feeling by now that the communication between the devices is bidirectional.If yes, then it´s really bad caps... Try to find low ESR caps for the replacements, that´s important ;-)Best Regards, LefterisGreece

author: hgg
author_rank: Frequent Contributor
timestamp: November 04, 2013, 07:35:28 pm
content: Lefteri if you help me fix it, the frapedes are on me!I just tried the 7V test and it looks like that the regulator might be sick...The 3V output went from 2.999V to 3V but the 5V output (middle pin) and base went to 7V !Do you think that this is the problemIf its the caps here as well, then its the most common problem in electronic repairs.Can't they just make a capacitor that works!?

author: AndyC_772
author_rank: Super Contributor
timestamp: November 04, 2013, 07:40:08 pm
content: Depends who you mean by "they". If you mean any of the reputable manufacturers, then they already do make reliable caps. If you mean the manufacturers that make cheap crap, then they don't. It's all down to your definition of "they".

author: hgg
author_rank: Frequent Contributor
timestamp: November 04, 2013, 07:47:02 pm
content: Andy if you have followed the repair of my SONY FH-909 stereo, it was a faulty relay but three of itscapacitors were bulging and they were Nichicons...

author: hgg
author_rank: Frequent Contributor
timestamp: November 04, 2013, 08:12:50 pm
content: I have also checked all the tantalum capacitors with the new DE REE DE-5000 LCR and they all have anESR of 0.14 @ 100Khz and a Tan D of 0.11 @ 120Hz except C11 next to the voltage regulator that has anESR of 0.30 @ 100Khz and a Tan D of 0.066 @ 120Hz. (although Tan D looks way better for some reason)Looks like that there is a problem with the regulator and its capacitor.Lefteri what do you think?(Ok, Update. U11 is definitely a voltage regulator with an output of 3V. Since the power supply is 5Vit cannot have a 5V rail as well. It only has a 3V rail. The only other place I can measure 4.9V is thelittle Q23 transistor below the buzzer's electrolytic capacitor. When I lower the supply voltage below3V a low battery error is displayed on the screen. I will replace all the tantalum capacitors and see whathappens.)

author: TrickyNekro
author_rank: Frequent Contributor
timestamp: November 05, 2013, 01:26:01 pm
content: What I see in your power rails seems to be something like an RF burst.An RF burst takes a lot of power, in a very short time. My best guess is this, I really don´t know mate.You are using the unit more than 10 years, or at least it is that old. Your power rails have that noise,which indicates that something is drawing a lot of power in short pulses and the pulses seems likedata. RF burst consume a lot of power, 0.5A, 1A depends on your output power really.Everything points to the caps, but you can never be 100% sure. Change them and let us know :-)Best Regards, LefterisGreece

author: hgg
author_rank: Frequent Contributor
timestamp: November 05, 2013, 05:46:33 pm
content: Hello Lefteri,I have ordered today new tantalum capacitors.The unit can be powered from mains and batteries as well. My main power supply has very littlenoise. When I power it up from the battery terminals, the ripple is much less but the problemremains the same. The battery power comes to the board from the big central ribbon connection.I will replace the caps and see what happens.Thanks!

author: TrickyNekro
author_rank: Frequent Contributor
timestamp: November 05, 2013, 10:56:42 pm
content: For testing you can also use electrolytic caps, just use at least 10x bigger values.When you can do it, it will be nice, in order to see the results.Best Regards, LefterisGreece

author: hgg
author_rank: Frequent Contributor
timestamp: November 06, 2013, 08:33:47 pm
content: I will update when I receive the tantalums.(I don't want to desolder and resolder the caps twice on the small smd contacts)Thanks!

author: hgg
author_rank: Frequent Contributor
timestamp: June 10, 2015, 05:53:53 pm
content: Hi,This is an old thread about the Vantage Pro2 wireless weather console, but I wanted to give ita second try. I was getting an error of "PLL not lock", and the console could not receive any datafrom the transmitter. The sensors transmitter works fine because I have another console.I've replaced some capacitors and the crystal but the problem remained. I did not get the error so often,but again no data. I measured the 5V & 3V voltage rails and they are spot on and without any ripple.The console uses the CC1021 single chip RF transceiver.http://www.ti.com/lit/ds/swrs045d/swrs045d.pdfIn the datasheet (page 12) it is mentioned than the typical value of the external clock is 300mVpp.The thing is that I measure 132mVpp.Do you think that this might be the actual problem?Thank you.George.

author: codeboy2k
author_rank: Super Contributor
timestamp: June 10, 2015, 08:33:46 pm
content: Quote from: hgg on June 10, 2015, 05:53:53 pmPage 12 mentions that the external clock should be 300mV , but they are not using an external clock, they are using an external crystal and internal oscillator.If you probe the pins with your oscilloscope probe you can load it down and make it either not oscillate, oscillate intermittently or oscillate at a lower amplitude than it would without the probe. The point is, you cannot easily probe a crystal and believe what you see.Do you have a function generator? If you think there is a problem with the internal oscillator then you can try to test it with an external oscillator from your function generator. First, de-solder the crystal and 2 caps. Then using a DMM set on continuity check, find out which pad of the crystal is connected to pin 10 of the IC. Set the function generator at sine out, 14.7456 Mhz , 300 mV peak to peak. Connect the function generator signal to that pad through a 10 nf cap as stated on pg 12 of the datasheet. Now you have an external oscillator at 300 mV p-pIf it locks better with the external oscillator, than you know there is a problem with the internal oscillator.So, if the internal oscillator is the problem, then the easy solution might be to make an external crystal oscillator on a piece of copper clad board to stuff into the device's case. NOTE: you cannot use a full voltage digital pierce oscillator here, i.e. the common 4049 or 74HC04 hex inverter oscillator that you can find all over the net. Using that will require re-programming a register internal to the device, and you don't have access to the software to do that. So you will need to keep the external oscillator within the limits that the software has programmed the radio, and that will be a sine wave oscillator between 300-600 mV, according to the datasheet. The software will not be programming the device to expect a digital square wave at full Vdd voltage.Google around for an oscillator circuit that is a 2 transistor crystal oscillator that can work up to 20 Mhz. That will get you a sine wave with buffering and enough voltage drive at the output. A single transistor oscillator will not have enough drive, and will be loaded down by the IC. You need a second transistor to provide buffering and voltage gain. You will just need to trim the output to about 300 mV p-p.You can also search for and use an opamp crystal oscillator circuit if you want to go that route, but you will still need to trim the output voltage to 300-600mV p-p.Here's a 3 transistor oscillator:http://www.seekic.com/circuit_diagram/Signal_Processing/Oscillator_Circuit/1O_2O_MHz_CRYSTAL.htmlSee also figure 1e and figure 4b in Linear Technologies AN12 -Circuit Techniques for Clock Sources.

author: hgg
author_rank: Frequent Contributor
timestamp: June 11, 2015, 05:57:31 am
content: codeboy2kthank you very much for your detailed instructions and explanation !!I will first try with the signal generator and see what happens.Thanks!(by the way when I probe the 1.8Mhz crystal of the ATMEGA128 I get 324mVpp)

author: hgg
author_rank: Frequent Contributor
timestamp: June 11, 2015, 07:17:11 am
content: ATMEGA128 crystal @ 1.84Mhz has an amplitude of332mVppTransceiver crystal @ 14.74Mhz has an amplitude of132mVpp.But when I probe them again with the oscilloscope & probeset to x10I getATMEGA128 @580mVppandTransceiver @600mVppSo the oscilloscope probes at x1 were loading the crystals but when set to x10the oscillators look okWhat do you think? Are the oscillators working according to the datasheet?or shall I give the console to my girlfriend?

author: codeboy2k
author_rank: Super Contributor
timestamp: June 11, 2015, 07:15:22 pm
content: You should always use x10 on your scope probe. I don't even use x1 anymore.Again, it's hard to trust when probing a crystal directly, but it seems like there is enough voltage drive there that it's probably ok in this case, as you seem to be getting reasonable values at 500mV - 600mVHowever, if you do have a function generator, I would still try it out. Your error is a PLL lock issue and that is definitely clock related, so it's still a possibility that the internal crystal oscillator on the radio IC is having stability issues. This might go away if you test it with an external clock source and then you'll know for sure. So if you have the equipment available, I'd still test that out.

author: hgg
author_rank: Frequent Contributor
timestamp: June 11, 2015, 07:41:53 pm
content: x10 made a difference indeed.Although the signal looks better, I am still not sure why the transceiver cannot lock the frequency.If you have a look at the attached picture, the transceiver sends on pin 10 a series of short andthen a series of long pulses. Immediately after that, it looks like that the oscillation begins.You can see that on the right top line. Sometimes the oscillation lasts for quite long and sometimes it stops immediately after the pulses. I removed the crystal and the loading capacitorsjust to see what happens and pin 10 showed exactly the same except the right thick line whichis the actual oscillation.The problem is that my function generator cannot generate 14Mhz... and I will try to make onefrom scratch. I have some of these 14.74Mhz crystals. I've tried connecting to pin 10 the outputof a crude crystal tester circuit I had with an output of 800mVpp and although PLL did not lock,it did not stopped trying even after an hour. Normally after 10 minutes if it cannot lock it willdisplay the error "PPL NOT LOCK" and will halt. I need to test it again with an accurate frequencyand 300mVpp amplitude. How accurate does the frequency needs to be?

author: PA0PBZ
author_rank: Super Contributor
timestamp: June 11, 2015, 07:47:31 pm
content: To me it looks like the radio chip is started, the CPU waits for the PLL lock and then when it does not see it in time it resets the radio chip and it starts again. Since you already replaced the crystal the problem is most likely in the radio chip. What are the chances you can get one and successful replace it?

author: hgg
author_rank: Frequent Contributor
timestamp: June 11, 2015, 08:01:43 pm
content: It looks like that its programmable. from the microcontroller(?)QuoteNot easy to find it but even if I do, soldering it successfully is another story...If it turns out that the problem is in the transceiver chip, then bye bye console.How often these kind of chips fail though?

author: PA0PBZ
author_rank: Super Contributor
timestamp: June 11, 2015, 08:17:00 pm
content: you don't have to configure the chip, the data is already in the Atmel controller.Quote from: hgg on June 11, 2015, 08:01:43 pmOnce too many I'd say

author: Deathwish
author_rank: Unknown
timestamp: June 11, 2015, 08:17:11 pm
content: Quote from: codeboy2k on June 10, 2015, 08:33:46 pm:schematic in first few minutes. I used it the other day and it runs with over a 20Mhz crystal

author: hgg
author_rank: Frequent Contributor
timestamp: June 11, 2015, 08:25:19 pm
content: QuoteBad news...I will build the oscillator tomorrow. Thanks for the video link. I will try the w2aew one which isbuffered and uses only two transistors. The amplitude though has to be 300mVpp. Can thiscircuit fine tune the frequency?How critical if the frequency accuracy. In the crystal tester circuit I have, the 14.745Mhz crystaloscillated at 14.742Mhz...

author: danfo098
author_rank: Contributor
timestamp: June 12, 2015, 07:17:28 am
content: Have you tried to do anything with the PLL loop filter (C55, C67, C57, R53 and R54)? According to the datasheet they use loop filter number 2. Check out page 48 in the datasheet for different loop filters with different bandwidths and corresponding lock times.Just probing the filter somewhere will change it for better or worse. Lowering the bandwidth should produce less jitter which is good but it will also increase the time to lock.

author: hgg
author_rank: Frequent Contributor
timestamp: June 12, 2015, 08:22:32 am
content: QuoteI've read that part but I haven't done anything with that part of the circuit.I've managed to build the 14.745Mhz oscillator (at 14.742Mhz..) with a nice sinewave, connected it topin 10 using a capacitor, but nothing. It still does not want to lock. Maybe the transceiver chip has failedafter all. Who knows.I might give it a last try with a proper signal generator.