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Clock-Signal Repair Pictures ISR4300, ASA, ISR4400

Bernhard Roth


We have many devices affected by the clock-signal issues.

Cisco does replace the units with repaired/fixed ones.

I have received some ISR4321 routers with the fix applied (pictures attached).

The Cisco provided fix is of - well - mediocre quality (loose solder joints etc..) but works.

I am an EE engineer and am able to fix other routers of my customers as well (attached a picture of one of my fixes).

Spot the difference :)

Is there anyone which has received fixed ASA5506, ASA5508 and ISR4331 routers?

Please post pictures of your fix (hi-res if possible)

I ask because I would like to fix them as well (some of my customers) and avoid configuration, license etc. migration.

I am aware that I might void Ciscos warranty by this act of evil :)

Best regards,


84 Replies 84

Bernhard Roth

Nobody with a repaired ISR4331?

Bernhard Roth

@cisco QA


Please check your repair process!


Yesterday I received a repaired RMA unit and guess what:

Loose wire (cold solder joint) on your fix which makes it - yes - inactive.

Router will breakdown within month/weeks due to clock-signal-issue.


Is tihs what you want to do?

Is this Cisco quality?


Guess not...




Hi Benhardt, nice hi-res pics ;-)


Thanks for the info, since I plan to purchase one a day off eBay (not for production purposes, of course, but for lab and training - I have to train myself on IOS XR).


BTW, very bad soldering on Cisco's fix, but I think that repair center are more targeted on production volume than in quality - I had a long ago an Asus mobo repaired by one of their centers, it was easy to find that they replaced an SOT23 transistor ... :-/


So, you added a 110R resistor as per EIA-96 marking on 0603 (?) case. Quick question though: on Cisco's fix, they removed R4 (named R4_CLK, 2R2) but you let it in place on you fix. Did you forget to remove it, or is it normal?


Thanks for your answer!


Have a nice day.

R4_CLK is still present on both models.

It's just the bit blurry picture which makes it hard to identify the component.


Thanks for the info. I would have bet to see a via under R4 (upper side of the picture) and rosin (resin) on the opposite side.


Have a nice day.

Just my two cents ...


I've purchased on eBay for my personal use a dead ISR4321 (clock issue), and I followed your procedure. I put a 5% 0805 150R resistor, soldered vertically on SOT23-5 device, and soldered a wire from the top of that new resistor to the resistor close to CPU.


No glue, no flimsy or loose resistor, device works flawlessly (I choosed the smallest 150R resistor I had in my SMD box, no matter tolerance).


I noticed that thermal pad was completely dry - did not help to have a 'cold' CPU. Replaced by Arctic Silver, and voila, done (be careful if you use that one, since it is conductive).

Hi all,

I recovered a 4321, and i found it is completely dead.  Just a short flash of one of the led's when switching on.  Fan does not start also, it moves a little bit.  


Is this what can be expected from the clock issue?  According to the serial number check, it is affected.


Especially the fan not starting makes me wonder if there is another issue with this router.


Anyway, i only have normal 150 ohm resistors in my shack.  Will buy some smd tomorrow.




Has anyone received a repaired 5506 yet?

Would also be very interested how cisco fixes it.

Here is what all of you have been waiting for:


Pictures of repaired ASA5506


Resistor is 150 Ohms, 0604 or 0402 SMD case.


Attached you can find an overview (spot the fix) and two microscopic (43x magnification) pictures, one of them at an angle to better see the solder joints.


That fix looks reasonable, much flux residue on the bottom but quite well done.

I will resolder them anyways and put eventually some liquid soldermask to protect the fix.


Feedback welcome :)



That fix is one of the easiest but you need some magnification to do it well.
On a scale from 1 (hard) to 10 (easy), ASA5506 repair scores a personal 7.

ISR4321: 6
ISR4331: 5 (many screws, big board)
ASA5508 & AA5506 (actually the same board): 3 small and fragile pads

As always practice good ESD protection, care and apply thermal paste when putting all together.



Is the middle resistor actually pulled? I can't tell from the photos you posted.




Hello Paul,


to which pictures are you referring to?




According to my findings, no components need to be "pulled" or removed.

All devices have only a resistor added (different values depending on model).

Thank you very much! Have a bricked (flashing amber) 5506 going to use for my lab. Do you think it was a 100 ohm 402 or 602 they used?


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