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TDS684C won't boot up - front panel lights stay on


Ryan Scott
 

Hi All:
I've acquired a Tek TDS 684C and it won't boot properly.  I'd like to fix it, but there is limited information available, and only to the module.  I followed the troubleshooting procedure from a 684a manual downloaded from Kurts w140 site.  Following the troubleshooting procedure, to the front panel/processor I have the clock signal and all the voltages are present at J2.  It states to replace the front panel module.  I pulled the module and could not find anything amiss.  I cleaned the menu buttons as they appeared dirty.  (thinking a leaky switch could hang the uP when it boots) When I powered it back up, it had more signs of life, but now it halts with a clock showing 9pm in the upper left hand side of the display.  
The display on the A11 board has the bottom horizontal segment lit.  - No other signs of life.
I cycled the power again (front panel) and it actually booted up.  
A quick power cycle (front panel) and it hung.  I don't think it's the front panel, when it booted the scope functioned as it should.  But now it's hung again.
Pulled the AC plug and cycled power again.  Boots.  Power on self test passed, signals displayed.  
It has the surface mount electrolytics on the front panel, but no leakage.  It also has the Dallas SRAM chips with the battery on chip.  

Power supply problem causing the uncertain boot?
Any other advice or ideas from the group?  
Thanks,Ryan ScottN7QJ


 

Try setting switch #3 on the processor to the off position. Also, if you can retrieve the error logs via GPIB it would help.

Jay


baltimora86
 

I would start by going over the power supply for obvious problems. Even though the SMD caps aren't leaking, it wouldn't hurt to check them for ESR if you can. The caps could have dried out if it was used or stored in a hot location.


Ryan Scott
 

An update.  I pulled the front panel assembly and took a look and like I said earlier, nothing seemed out of place.  I did notice some crud around the scale encoders.  Perhaps someone used some contact cleaner on it?  Cleaned it with IPA and after 2 power cycles, it's booted just fine off and on for the last week.  Not really sure what to make of this.  It was 'scrapped' at my work from a remote design center as 'unrepairable'.  The back cover (collar) was missing so it's obvious someone was into it.  From the limited troubleshooting guide I found, everything pointed to the front panel.  The clock signal and all PS voltages were present.  The only thing I can think of is whatever someone may have used to clean the control or whatever crud I found was leaky and causing the boot sequence to hang?  
So far I've ran it through various exercises and it's all good. It's a great scope.  So I guess I'm going to run with it.  
Question:  It takes about 30 sec to boot up.  Front panel lights, then screen flashes, then a 'clock' then clicking followed by the starting screen saying it's passed the power on self test.  
Is this a normal boot time?  (I'll verify it on a 784 at work tomorrow)
Thanks for the time guys.

On Friday, February 13, 2015 8:42 AM, "acuffe@gmail.com [TekScopes]" <TekScopes@yahoogroups.com> wrote:


  I would start by going over the power supply for obvious problems. Even though the SMD caps aren't leaking, it wouldn't hurt to check them for ESR if you can. The caps could have dried out if it was used or stored in a hot location.

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