error fpga fan speed

The engineers at FlexRadio read the community, but we're busy and don't read all the posts.  Tim does read most everything here and if he feels like we need to weigh in on a topic, he shoots us an email and asks us to do so.  Such is the case with this thread.

First, I suspect that denying that we're the kind of company that would do something to increase service revenue probably wouldn't dissuade those that think this is the case.  It is, of course, not the case.  We are all "craftsman" that design radios and any failure reflects on our design and disappoints us.  We want the customer to get any problems fixed quickly and inexpensively.  This is true of most engineers regardless of any management directives to the contrary (which also don't exist at FlexRadio).  There are numerous cases that can be found that demonstrate this (including the recent high profile diesel emissions problems).  Engineers are generally more likely to be incompetent or accidentally make a bad choice than they are to actively "cheat" a customer in my experience.  FlexRadio's management team is also honorable and would not ask customers to pay for a problem just to charge a customer.  We have a demonstrated history of fixing problems that most would consider to be our responsibility at our own expense (FLEX-3000 preamp, FLEX-6700 performance enhancement [PEN], etc).

We discussed the fan failures that have occurred and our preference, generally, would be to give a customer a part number and suggest they fix the problem if it is easy.  Internally, we have been fixing the issue by replacing the integrated fan and heat sink assembly.  Removing the heat sink from either the CPU or the FPGA is not a job for the faint of heart.  The adhesive is strong and is designed to firmly hold the heat sink to the chip.  Each of the chips are connected to the PCB by either 464 or 1031 solder balls, depending on the part.  If you were to break any one of these loose, you could have a failure or intermittent radio.  Sometimes customers that cause issues like this do not feel obligated to tell a company what caused the problem (I'm not accusing anyone in particular -- just saying I've seen it happen as a radio repair tech).  This results in hours of bench time trying to find the problem and then customers sometimes suggest that we should pay for the time it took to find and repair the problem.

I'm sure it seems odd, but it never occurred to me (or anyone else at FlexRadio that I know of) to remove the fan from one heatsink/fan assembly and **** it into the already attached heatsink.  We buy them as an integrated unit.  But, having seen this here, this is a simple enough fix that I think most of our customers could do this.  Opening the cage, who's sole purpose is to prevent radiated emissions from the processors, memory and power supplies from reaching the radio, is not too hard -- but putting it back together correctly is much more difficult.  If the cage isn't closed properly, RF from the cage will end up in the receiver.  Many of the developers at our office run the radios with the cage open because we need to take measurements, etc. and we see first hand the effects of this and you do not want to run your radio without the cage.  *I* do not close the cage myself, but instead have the service team do it and I'm very comfortable doing SMD rework, etc.

So the official FlexRadio position will remain that we consider opening the cage to be a "non-customer serviceable item" because of the difficulty opening/closing the cage.  If you open the cage, it will void the warranty.  If you are out of warranty and want to replace the fan and you feel comfortable spending the time learning how to close the cage effectively, I think it is something that many people could do -- but it's not terribly easy.  If you get stuck and call service, I would expect our service team to charge you to teach you how to get the cage closed or deal with any issues you have.  I don't feel that this is in any way unreasonable.  It's really no different than fixing your car: if you buy a Chilton manual and it looks like you can accomplish the repair yourself, great.  You buy the tools and the parts and perform the repair.  If you get into trouble, you have to get your car to the dealer or local repair shop and pay him to help you get out of trouble.

Please note that the fan must have a tachometer.  The fan we use is also available without a tachometer and if you purchase the incorrect one, it will install fine, but the radio will not enable the power to the chips because the fan is apparently not spinning.

Not to frighten you, but I have a funny story along these lines.  The first vehicle I bought myself was a Honda XL-350R motorcycle in 1986.  I wanted to perform all the repair and maintenance work myself.  The first thing I did on my new bike was to change the oil.  I bought a service manual that said I really needed a torque wrench to properly tighten the bolts on the bike.  I went to Sears and bought a torque wrench, an expense I didn't want.  I changed the filter and went to tighten the three bolts that attached the oil filter cover to the block of the engine.  I looked up the torque which was expressed in Nm.  I tightened the first bolt and couldn't get it to the required torque so I continued to twist the wrench.  Of course, it has a long handle and a lot of mechanical advantage.  Suddenly, it got easier and before I knew it I was holding the bolt head in my hand and the shaft was sheared off inside the engine.  You can imagine how I felt.  I called the Honda dealer who was puzzled.  He asked what value I was torquing to.  I replied with the value and he said "Where did you get that?"  I said "Right from the service manual on page <whatever>.  It says torque 8mm bolts to 18Nm." (values are no longer accurate as my memory has faded).  He said "it's a 4mm bolt tough."  I said "No, the socket says 8mm."  He laughed and said that the bolt size is the size of the shaft -- not the head.  You can see how I made the mistake and you can also see how it's a **** newbie mistake.  The dealer offered to fix it for me by drilling out the bolt, but said "I can't guarantee that it will not destroy the bike -- the engine is magnesium and if it catches on fire while I'm drilling it will just burn to the ground."  It all ended well and the drilling was successful with even more money out of my pocket. 

My point in telling this story is that the service department at Honda could not have predicted the **** mistake I would make.  And I did not expect them to pay for my **** mistake when I made it.  My advice to those that want to make this repair themselves is just like it would be for someone repairing a car, etc: feel free to do it if you feel qualified.  If you mess it up, it could be expensive to get out of trouble.  I know this sounds a little like I'm trying to scare you off of doing the repair yourself which is not the case.  I just want you to understand that you're dealing with an area of the radio that could be expensive to repair if you make a serious mistake.