Philips PM6665 Frequency Counter - Fire Hazard?

[cio74]

Hello,

I have bought this on Ebay "for parts or not working" due seller being unable to test. It was fine, just the C hole damaged. Cleaned it up, power it on, it was fine. I did open it and look inside and couldn't spot anything wrong.

After a few hours of running I put it on the shelf and it sat there until today. Build a VFA and wanted to check the frequency output.

All was fine, left it on for dinner and when returning there was a burnt smoke smell in the air. Rushed to check the soldering station, power supply - but these were off. The 2 PC's were running fine, so did the LCD's. I just couldn't spot it for minutes, everything was running, the frequency meter included. I then decided to unplug the Philips just to clean the desk space. I have no idea why I decided to smell it but that's when the smell hit me hard. There was some kind of slime on one finger, feels like oil.

I took a couple of pictures and the only thing that seems to be damaged is the power in socket which has a diagram where a couple of capacitors can be seen and which I believe relies the problem. It's easy to spot the slime leaking around the AC socket.

Question is, what could have caused this thing and if I was not to come in about 15 minutes, could have actually set on fire?

[Gyro]

Looks like the X capacitor inside the Schaffner IEC mains filter failing. Not uncommon - on HP gear too. Not a fire risk as such but messy and smelly. Unplug it and replace the filter and you should be fine.

[bktemp]

It is the infamous SCHAFFNER mains filter. There is a X2 capacitor inside that fails after some years, because its case cracks and moisture gets in. When you apply power it goes bang.

[cio74]

I remember last time a cap exploded, it's been quite nasty. It looks I've missed the show this time.

The part is obsolete, it is very likely that I won't be able to find one with the exact L and C values, looking to replace it with a newer part, I take pretty much any in line filtering will do as long as it fits?

[Gyro]

Yes, that will be fine. Your's is complicated a bit by the right angle wire entry but as long as you can find one that still allows safe insulation clearance from the transformer then go with it.

Worst case I guess you could probably get away with an ordinary IEC connector but some degree of filtering would be beneficial.


P.S. I doubt if you missed the bang this time, more like a 'Pfffut' and a jet of smoke. 

[cio74]

Cool, thanks for the tips

[jackenhack]

The PM6665 is a great little unit. I did a replacement card for the crystal oscillator, using an OCXO from eBay. After calibrating against my GPSDO, after it warms up it's still bang on now a year later. Great upgrade for $20.

http://www.jackenhack.com/philips-fluke-pm6665-pm6669-ocxo-pcb/

[james_s]

I've had the same problem with an old Apple II computer. X2 capacitor across the power input failed a few minutes after it was plugged in, the computer wasn't even on. Made lots of smoke and smelled terrible but these things are designed to fail gracefully and not catch fire.

[artag]

I had a PM6666 do exactly the same thing, and plenty of devices where the X capacitors aren't hidden in a tin have died too. It's just something that happens to 20+ year old equipment.

I can't remember where I got the replacement (wire ended, side exit) IEC filter from, but it took me a while (especially as I had another counter so wasn't in a hurry to pay full price).

[james_s]

I've always salvaged those line filters from various scrapped equipment. Back when CRT computer monitors were common and had little value I pulled filters from several of those I scrapped. I've also found them in various IT equipment I fished out of the e-waste bin at work. If you can't find one I can probably send you one that will work but shipping overseas may cost more than the part is worth.

[HighVoltage]

This is very typical for Philips counters PM66xx and when I still had them, I exchanged the SCHAFFNER power connector on all of them.

One exploded so badly, a lot of tar came out and placed itself on the PCB, that was very nasty to clean up.

[SingedFingers]

At least the X2 cap is in a nice box in those filters. The one that blew in my Philips scope made a right mess!

[rachdatu]

Hello

On the same subject, a few years later, with a Philip PM6666 Timer/Counter.
I was about to start playing with that device and its GPIB port. I have updated an old PC with an old GPIB ISA board, installed Linux antiX on a bootable USB key, GPIB drivers, etc. So far so good...

I switched on the device but then I decided it was time for a well deserved coffee, so went downstairs (3 floors) in the same house.
After a couple of minutes, I heard a "bang". At that time, I didn't know if that were the breakers or what.

I ran upstairs as quick as I could (very fast) and then I saw the magic smoke. It was surprisingly quiet. All 3 computers were off.
I thought, well, the breakers did their job :-)
It was stinking like crazy and smoke was still escaping from the device.

The obvious culprit is the input filter (Schaffner FN 326-1/07). I have found a replacement in my bin (IA5-H33).
I still need to put the device together, will let you know how it goes.
Some pictures below.

By the way, how do you clean that mess?
Thanks

Walter

[HighVoltage]

Welcome to the forum

Yours is not too messy, you got lucky.
In my case I cleaned it with some cleaning benzine and lots of cotton towels, it worked very well.

[rachdatu]

Ok, thanks

I used "white spirit" and the result is not that bad. But the smell is still there ...

The length of the filter is fine (not touching the transformer) and the device is working as before. So, success !

Walter