Greetings,

We have some custom equipment running on 208 VAC 60 Hz in the USA. ?We originally used Schaffner line filters with rated voltage and current specifications allowing for acceptable safety margins.

Several of these input filters exhibited catastrophic failures.

Upon close examination we found that the “plastic” insulator on one of the filter output terminals appeared to suffer thermal damage (more or less melted) allowing one of the line terminals to move through the melting material and make contact with the grounded metal housing. ?Thus the “big bang”.

I too recommend replacing the filter with a different unit because it does protect the scope from inbound transient noise.

Regards,

Ken

On 2Feb, 2020, at 3:35 PM, Paul Bicknell <paul@...> wrote:

Hi Andre

?

Most of us have had this experience ?and as we use 240 volts in the?UK?we see it quite often?

?

My best advise is to replace it with a good quality one from a reputable supplier such as digekey ??but not amazon?

The worst you could do is wire it out as the filter also stops noise coming into the equipment?

Paul?

---

From:?[email protected]?[mailto:[email protected]]?On Behalf Of?Andrelhermanus@...
Sent:?02 February 2020 21:21
To:?[email protected]
Subject:?[HP-Agilent-Keysight-equipment] Schaffner Filtered Power Entry Module (HP54504A 400MHz scope)

?

Hi
I have the HP54504A 400MHz oscilloscope whose filtered line input module suffered catastrophic breakdown (a cloud of smoke with brown goo emanating from the on/off switch) I wonder if one can use other versions of these online filters or must it be the exact one viz. FN393-2,5-05-12? Any idea what would happen if I bypassed this filter temporarily.?

Thanking you
AndreH?

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I've owned and maintained many printers over the years, and found that it's a crap-shoot finding detailed info about the innards. There's some stuff out there on various makes and models, sometimes found in discussion groups, or from people that sell the inks and toners and such. After enough experience and disappointment with HP, Epson, Canon, et al, I long ago decided that Brother brand printers were the best for low cost, long term reliable running, and maintenance. They have been my favorites for at least a decade, and the only brand I would buy.?

About a year or so ago, my old HL-4040CN color laser crapped out, with some error code indicating the problem. It turned out that I had a pdf of the entire factory/shop service manual (several hundred pages) for it, that I had stumbled upon years earlier, while looking for something else. I dug up the manual, and determined that the laser scan motor had seized up. The manual has all the info needed to diagnose and take everything apart and replace modules, but I went a step beyond - I took the motor apart, cleaned it out, re-lubed the bearing, and it was back in business. I think normally, the entire optical scan unit (probably more expensive than a whole new printer) would have to be replaced.

More recently, it crapped out again, this time due to failures in the belt unit and other disposables. I can't really complain about this, since these consumable parts had never been replaced, and had run way past their normal life expectancy. At this point in the life of a printer, you have to weigh the cost of the replacement items versus getting a whole new printer. I decided to retire the 4040 and junked it out, even though it probably could have gone for a few more years. In its place, I have parked a HL-3040CN of similar vintage, that I've kept in reserve. When this one craps out, I'll get a brand new Brother whatever color laser. I don't know if I'll find a manual too - I guess I'll see when I get there.

Anyway, luck with keeping printers going and finding info is very variable, but since they have become such commodity items, it's not a big deal to attempt simple repairs even without much info to go on. There's not that much to lose if you make it worse. Sometimes even banging on stuff - like the the old TVs from way back - can make a difference.

Ed

So far - no hint of a glow, even in complete darkness. There's no beam finder control; there are position trimpots on the front which didn't bring anything into view. Verified (with power off) filament continuity (temporarily disconnect filament lines from HV board to CRT). No sign of residual light during power down. Also, sometimes when I turn on old-style oscilloscopes I hear a "crackling" sort of sound (as the HV comes up); no sign of this here. Status LEDs are lit except for the LED reflecting the 158V output of the display section power regulator - the test point where that LED is located is showing ~168V (supposed to be 158V.)