DSO6014A PLL Unlocked error. Help needed.

[simonov]

Hello,
My deal on DSO5014 didn't go well and I purchased this used DSO6014A. The seller parted with it for just $280. The scope needed a lot of cleaning inside so it was disassembled and I gave it a bit of a TLC.

The scope does power up and boot. The boot sequence on the front panel seems OK. The scope then shows the following: " The oscilloscope setup defaulted because a software fault occurred. Please report the following diagnostic information: PLL Unlocked"

The front panel controls do not respond. The scope doesn't do anything else. The Auto trigger blinks (on the screen). From time to time (if I hold start button while powering up) the scope boots into battery power mode (although it has no battery).

I've tried providing the scope with external 10MHz reference from my rubidium standard but the result was still the same. The main power board works fine and gives +15V which should be fine.

Any thoughts on this would be welcomed.

[Bud]

Identify the clock generator on the board and look around it, maybe you knocked off a capacitor or inductor while cleaning the board. You can post a good res photo of the board here so people can help you find the PLL chip (if there is hardware one).

[simonov]

Hi Bud,
thanks for the reply.
Just to clarify - the scope was in this condition when I purchased it. I knew about this error beforehand and It was present before I opened the scope. I will upload more photos soon.

[simonov]

I've taken some photos. The PLL is located below the ADC's. It is the LMX2306:
https://www.farnell.com/datasheets/4907.pdf

The main oscillator is V515ME01-LF
http://en.planetec.com/product/datasheet/V515ME01-LF.pdf

The digital logic around those is supplied by the local regulator U1912 which gives 3.3V. The supply voltage is OK. When powered off the DC resistance around the capacitors in this rail is suspiciously low - around 40 Ohm. The regulator is very hot. The capacitor around U1905 is not looking good. It has some yellow goo around it. It looks bad.



It is possible that some bad caps are causing the problems.

[Bud]

OK so now you  have something to work with. Per the datasheet, pin 14 may be configured to output lock detect signal, check what you have on pin 14 as per section 1.3.2 in the Datasheet.

[simonov]

There is nothing on pin 14. The supply pins have RC filters R=17Ohm, C=100n. I measured the voltage drop across the resistors and there is nothing. I expect around 20-30mV Vdrop. I can only assume the PLL chip is not working.

The 10MHz reference is present on pin 8. The oscillator is HG-2012JA and gives.

https://datasheetspdf.com/pdf-file/514200/ETC/HG-1012JA/1

[Bud]

Maybe it is in power down state. What do you have on pin 10?

[simonov]

Hi,
pin 10 is hard wired to +5V.

[qzqmom]

hello any progress？i bought two dso3062 one ofthem has the same symptom ，seller said this fault because of longterm idle ，i wanna have a tray ，may be bad Crystal oscillator ？this part truely has a high fault rate

[simonov]

Hi,
I'm waiting for some spare PLL IC's to arrive. I will also swap the capacitors around this area on the 3.3V rail.

[qzqmom]

recorrect the type is Dso 6032 . ship to me tody，Alredy fixed one of channel problem. they are so dirty😅， now i will work on pll unlocked error . i plan compare two osc round circuit and try to find some abnormal.
​interesting when i test the vco rfout，after a power circle the fine oscillospe also report PLL unlocked error. that scared me😥 then i try to short memory battery and restart . finally it recovery maybe this error can storage in rtc memory once occurd system will halt until a factory service.
short memory for the error one is useless. so there still some wrong on the pll clock circuit

[qzqmom]

rf out frequency between two oscilloscope healthy one power on is 490mhz raise to 500mhz then locked another power on also490MHz but amoment jump to 550mhz .seem that pll lose control and add frequency to the max may be feedback singal have problem

[simonov]

Hi,
perhaps try and measure if the PLL chip is working the same way as I did?

[qzqmom]

i think pll chip is working cause the frequency of vco have a junp . I also try to remove the 10mhz reference osc but get the same result .maybe problem exists Interior of the chip .I alredy bought ICs for the replacement. they will arrive in a week.

[qzqmom]

Good news！After repalced the lmx2306 it still say PLL unlock but after a power cycle it did work ！must be the problem of lmx2306 thisicis so chip may be have a high fault rate。I bougt five only cost $1

[simonov]

Hello,
that's really uplifting. I'm still waiting my parts from China.

[simonov]

Hello,
I'm happy to report that my scope is working now. The PLL chip must be problematic in these units. After replacement the scope went to self reboot and the next time it came up working.