Hamitup not working

[wec...@gmail.com]

This is a 2nd post, so please disregard if duplicate.

Gentlemen,

I have a brand new upconverter that is not working.

The oscillator produces no output when properly inserted.  After troubleshooting against the schematic, I see that pin 1 of X1 is directly tied to ground (according to my DVOM) but actually should be connected to IC8 pin 1 (OSC ENABLE)  

If I lift the leg 1 of the oscillator, I then can see 125MHz at leg #5

BUT, I do not see any 125MHz at either IC8 pin 4 or R2 (start of OSC attenuator)

Also, IC5 is VERY HOT to the touch.  Not sure if this is normal ops.

Please advise as this is a brand new unit.

Greg Weremey - Electronic Service Pros.

http://www.esprepair.com

[Opendous]

>Also, IC5 is VERY HOT to the touch.  Not sure if this is normal ops.

Yes, that is clearly wrong.  IC5 buffers the path selection signal from the toggle switch at very low current levels so if it is hot it is broken.  There must be a short somewhere around it.

[Opendous]

Here is a repost of the Upconverter page comments related to this issue:

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Comment by Greg, Jul 10 (5 days ago)

There is a design flaw in the 125MHz version...

I recently purchased a new upconverter and found that not only did it not work (no oscillator output), IC5 got very HOT. I decided to tackle the project myself.

After troubleshooting against the schematic, I see that pin 1 of X1 is directly tied to ground but actually should be connected to IC8 pin 1 (OSC ENABLE)

If I lift the leg 1 of the oscillator, I then can see 125MHz at leg #5 of the oscillator BUT, I do not see any 125MHz at either IC8 pin 4 or R2 (start of OSC attenuator)

Also, IC5 is VERY HOT to the touch.

I remove the Oscillator DIP socket and find no solder jumps or shorts.

I then focus on IC5. I find that both outputs (pin 4,6 of IC5) are always LOW no matter which position S1 is in. After tracing the board, I remove JP3 (a 0ohm resistor above IC6 (RF IN SW). This disconnects IC8 and removes the short...IC5 now is cold and it's respective pins (4,6) now flip HIGH (3.3v) depending on position of S1

So the problem is somewhere between JP3 and IC8.

The SMA jack for the RF INPUT is the culprit! Upon assembly, there is ZERO CLEARANCE between the ground pins of P1 (SMA jack) and the two traces underneath those pins. The legs of the SMA jack scrape the coating off the PCB and SHORT OUT those traces. Once the SMA jack is removed and the board carefully inspected, normal operation resumes. The problem is ONLY with the INPUT jack.

This is an easy repair. Once can simply use a short pigtail of coax here. In future models, I hope the design team moves those two traces so that they do not lie underneath the back of P1.

The upconverter works VERY WELL. Congrats to the team for producing a fine product.

73, Greg Weremey N1JFE - Electronic Service Pros. http://www.esprepair.com

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Comment by NooElec, Jul 11 (3 days ago)

Hi! I am an employee of NooElec, the company who manufactures this upconverter design in conjunction with Opendous.

The problem you describe is quite intriguing, as we have produced thousands of these units and have not yet encountered this particular problem in production. The fact that it somehow also made it past our QA team is further cause for concern.

We will be happy to have your board replaced for you (fully at our expense, of course). It may prove beneficial to also get that board back to our lab to try and ascertain the exact reason for the failure. It is likely you are correct, and an out-of-tolerance SMA connector scratched and shorted the PCB, but such boards should certainly not end up in the hands of our customers.

You can reach our support team at support AT nooelec DOT com, or through the contact tools on our website. Thank you for your in-depth analysis and kind words!

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Comment by project member opendous, Today (moments ago)

>The SMA jack for the RF INPUT is the culprit! >Upon assembly, there is ZERO CLEARANCE between >the ground pins of P1 (SMA jack) and the two traces >underneath those pins

Thank you for the in-depth analysis. Routing under the SMA connector was a compromise to maintain a solid return path for the RF signals. On the vast majority of boards the solder mask is enough to protect the control signals from shorting.

>moves those two traces so that they do not lie underneath the back of P1

That is going to be very difficult. Since the board is 2-layer, there is no easy option to route a control signal without breaking up the return paths for the RF signals. I considered using large (1210) resistors as jumpers but cost constraints reared their head.