Electronics > Repair
Fluke PM6666 counter freezing after 3 seconds from turning on.
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FransW:
I know and I am willing to do so.
The only thing is, I have to scan it.
And that will take quite some time or I have to rely
on a scanning service.
pizzigri:
Wow, that is absolutely great!
Thank you FransW

As for what information is most important now, well, I imagine the part where the bus logic is explained, so I can try to understand where the whole process hitches and freezes the counter... I cannot believe the I2C logic is flawed, as the whole counter uses this bus and if a GPIB I/F is not connected to the counter mainboard, the thing works flawlessly. There must be something happening in the first 3 secs that hangs the machine. If I could pinpoint an IC, hopefully NOT the custom OQ0501 I, maybe I can replace it, or otherwise test it.
Of course I would be interested in the whole manual, once it is available!


all my best,

Franco
pizzigri:
BTW, since the PM6666 is totally disassembled, I imagined I could take a few pics of the only option that I could not for the life of me find images on the web - the PM 9607 - 00 10Mhz high stability time base option, in other words, the MTCXO card. I took the copper shielding off to show the components on the board. It uses a Philips crystal that is actually encased in glass, I haven't seen many of these enclosures.
The values are stored in the 85c82 eprom; there'a also a hex ubuffered inverter MC74HCU04N and a LP2951 voltage regulator, plus an IC I cannot ID. The Fluke literature says that ..."The unique MTCXO principle gives a residual temperature stability of 2 x 10-7 over the temperature range"... and that it equals the stability of an oven XO, of which I have some doubts.
However here's the images.
coromonadalix:
niiice a transparent crystal,   i dont catch why there is an eprom   85c82   IC403 if im not mistaken     what is the part number of ic402 ??
pizzigri:
The EPROM stores the drift values recorded at the factory for this single crystal at a range of temperatures. As the sensor measures the temperature, these values are used to correct drift, hence “mathematically controlled, temperature controlled XO”...
I can’t read the markings on IC 402, and there is no schematics or pcb detail in the “old” manual for the MTCXO, only the standard oscillator. I suppose it’s a microcontroller. Maybe in FransW new manual there’s a schematic for it!

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