This sounds like a reasonable (and effective) installation method.

So I thought. Lot of good it seems to have done for accuracy!

Earlier I see the XBees have 10ED firmware version. The latest on the Digi site seems to be 1xEC. Is that the firmware they came with?

Cool, so the two talk back and forth ok, so the XBees are fine. Now I'd put the chip back in, remove the shields, and see if the Arduinos will talk back and forth with the TX and RX lines cross-coupled.

Did they solder the crystal's body to the board?

The datasheets for the crystals I bought said specifically *not* to do that.  The heat of soldering can crack the crystal.

As I recall, the boards I used kapton tape to hold the crystal closer to the board perform slightly better.

I use a small drop of gel-type super glue to hold the crystal to the board. Then I solder one lead at a time, with a micro alligator clip on the crystal lead as a heat sink, and taking care not to heat it longer than necessary.

I recently did some accuracy testing on a half-dozen DS1307 breakout boards. After letting them run nearly 10e6 seconds, the errors were -44, -30, -28, -20, -7, and 14 ppm. Five of the six had parts I bought from various sources, and while the crystals were not all identical, all had ±20 ppm specs, and I believe all were 12.5pF. The sixth was a kit I purchased, so I'm not sure about that one (the kit had the -30 ppm error).

So pretty disappointing. I'm a fan of the DS3231 too. Simultaneous with the above tests, I checked a Chronodot that had run nearly 1.5e6 seconds, and it was 1 ppm off. Thank you, macegr!

Not a scientific test, small sample size, etc. etc., but I still found it interesting.

Ok, I got it off any specific operations you think I should perform?

Good deal. You have a terminal program? CoolTerm or TeraTerm or whatever? Start two copies. Put one XBee on the Explorer, the other on the Arduino without the MCU. Connect one of the terminals to each. See if both will respond to commands OK. When they're not in command mode, whatever goes in one should come out the other.

Is there any way to pull out the microcontroller with lowest riskof breaking it :o just tried pulling it a little, it's really in there...

They can be tough to get started. I use a very small flat-blade screwdriver, work from one end then the other, little by little. I think there's really little chance of breaking it.

The other thing to try is to take the shields off, wire the TX from one Arduino to RX on the other and vice versa, see if the little test sketch works that way. Just trying to eliminate some variables. But if that works OK, then I'd still want to test the XBees standalone.

Yep just found that, thanks. You could use the explorer for one XBee and do this for the other:

With the jumpers in the USB position (i.e. on the two pins nearest the edge of the board), the DOUT pin the Xbee module is connected to the RX pin of the FTDI chip, and DIN on the Xbee module is connected to the TX pin of the FTDI chip. This means that the Xbee module can communicate directly with the computer - however, this only works if the microcontroller has been removed from the Arduino board. If the microcontroller is left in the Arduino board, it will be able to talk to the computer normally via USB, but neither the computer nor the microcontroller will be able to talk to the Xbee module.

Thanks, the pic helps! Where do the shields come from?

Well? I still don't have an inkling as to how to fix this problem... This is pretty serious too, wait 'till you guys see this gem...

I am really surprised to see that nobody else has had this problem, at least I haven't been able to find a thread similar to this for the past couple of days...

That is a gem all right. Darn things behave pretty well for me. Any chance of trying the XBee-to-XBee thing without the Arduinos? I'm not entirely clear yet, these are Series 1 Pro models? (A link or exact model number would be great) What are you using for adapters and how are they powered?

Of course the answer is "It Depends".

When choosing between name-brand manufacturers like On Semi, Microchip, TI, etc., price wins if everything else meets specs. OTOH, I've had good luck with the "Various" company as well, especially for the items that are more commodities like voltage regulators, diodes, etc. The more specialized components will tend to be sourced by fewer manufacturers so that naturally limits choices. Sometimes physical size wins with things like capacitors. If you're just a hobbyist like I am, then surplus parts can be a good value, but if/when the supply dries up, then physical size or specs can change which might be an issue if you're doing higher volumes. If all else is equal including price, I will favor a known brand name over a no-name (multicomp, various, etc.) part.

Can't say that I've had any quality issues with anything I've bought recently, whether brand names from Mouser or Digi-Key, surplus from various suppliers, or parts from sources in China or Thailand.

... the rate that the first XBee talks to the other XBee, the rate that the second XBee talks to the other XBee ...

I'm not aware that these are observable parameters, let alone configurable. My understanding is that how the XBees communicate to each other is a constant, and is independent of the settings for their local serial port, even to the extent of AT vs. API mode.

What might not be so obvious is that the 6 rates all need to be the same, so that the Arduino and XBee can communicate, since you are using the same port to talk to the PC and the XBee.

I'd be very surprised if I could not configure two XBees for different baud rates and still have them communicate perfectly. In fact, I'm pretty sure I've done this with the S2 modules. falven is using S1? Is there something about the S1 modules that is different from the S2 in this regard?

If it were me, at this point, I'd get the Arduinos out of the loop, and just try to make the XBees talk between each other, either with two terminal programs running on one PC, or one terminal program running on each of two PCs.

Mr. CrossRoads,
Please ... Jack is fine!

Yes, they do, I'm attaching it and the CAM file since they're doing the blackout thing. I'm pretty sure they're original...

But really. With tube rectifiers, they run hot, waste power and fail more often then any other type of tubes. I usually just build a diode replacement  when I encounter tube rectifiers.

True that. Are there any special considerations when substituting solid-state rectifiers for a vacuum tube? I mean other than the obvious voltage and current specs. Was going to try it years ago on a ancient surface grinder that had some pretty scary tubes providing DC to the magnetic chuck, but never quite got around to it.

Solid state rectifiers are the only REAL rectifiers.

???  I can probably lay my hands on a 5Y3 here without a huge amount of trouble