Electronics > Repair
Fluke PM6666 counter freezing after 3 seconds from turning on.
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pizzigri:
I have traced the I2C bus in the PM6666 and 69.
The whole device is based on this bus, it connects all subassemblies - display, oscillator, to BU105 connector that is used for both IEC (GPIB) bus and optional internal battery and it also goes to the undocumented connector on the rear. In the PM6666, the I2C bus also goes to the input amplifier, to the three PC8574 ICs (I2C bus expanders) connected to a PM7528 Dual DAC, all missing in the simpler, one input amp of the PM6669.

The I2C bus goes to both the CPU and custom IC, and I cannot understand why plugging the IEC - GPIB board freezes the machine. If the Custom IC was bad, or there was something wrong with the I2C bus, I would see malfunctions, and I dont. I can leave it on all day and it will work flawlessly.

So I looked at which other lines are connected to the IEC bus, and found that there is a "option" line that gets connected, going to pin 12 of the CPU, which is an external interrupt (labelled INT/TO), vs. the "ident" used by the prescaler and oscillator (these lines tell the CPU if a MTCXO is installed so that a single button press calibration is available, and if the prescaler installed; I did in fact install the prescaler and it works without a hitch.
But even if the option line int causes a crash, why does it happen three second after I turn on the machine? I would imagine it would be immediate.
An idea could be that there is some corruption in the programming of the CPU (stored in the internal 6K), but I would not know how either to test this or correct it.
I have an hobbyist oscilloscope (SDS1202x-e) and good multimeter, but that's all I have... is there something I can try to troubleshoot this thing?

coromonadalix:
Nice detective work

Could it crash when enumerating the i2c peripherals ?

A data sniffer like bus pirate or salae logic probe / clones on Ebay  ??
Ordinaryman1971:
Far fetched idea but... maybe your firmware is somehow corrupted. Let me see if I can burn the copy of of my counter.
Could you see the version you're running?

I know it's silly for me to ask... but did you inspect everything for possible shorts... the seller stated that the meter is working fine.. so, lets assume that he did in fact turn it on and it was working, then... something happen in transit.

What is the frequency of the prescaller you've had installed... can it go more than 1.1 GHz, that's what I have in mine. Actually I've tested mine some time ago and it goes all the way to 1.6GHz.... and I have standard time base btw..
pizzigri:
No, I don’t think there’s any way to see the fw rev, however the board is rev 12, and the counter is branded Fluke.... built possibly in 1998 or 99 one of the last manufactured. The prescaler is the “B” version, it goes to 1.3ghz.
I took the whole thing apart, as I wanted to add lcd illumination - the screen is horribly hard to read, just like my old PM2534 - and I could not find any shorts, actually the counter seems brand new, clean and tidy.
The PM6669 I got as a great deal on ebay was used and abused, scratched, splashed, dirty as hell.... but works perfectly. Frustrating
FransW:
In the men time I received this manual:
Timer/Counter PM 6665 and PM 6666, Service manual, 9499-465-01311, 90-10 Second edition, 132 pages.

It will take me quite some time to generate a complete pdf version. The manual contains fold-out A3 size diagrams in color.

To contribute something I refer to the attachment with an introduction to something called "Extended Test Program" which I gathered as important.

Attachment 1: Extended Test Program
Attachment 2: historic overview GPIB parts lists

Frans
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