EMI Filtering

Low tech: Use a burn barrel. ;-)

Get a 1:1 isolation xformer for the shredder.. It's most likely the universal motor being used and the brushes arch in those.

Arch? You're as stupid as dimbulb. Maybe even a notch lower.

An EMI filter pulled from a junk PC power supply and installed at the motor would do more good, since the RFI is radiated by the wiring inside the shreader

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Long ago, I had a computer that would drive my X10 lighting system nuts. I had to add a line filter (some Ls and Cs, I assume) on the power plug. So, this was a conducted emissions problem.

I suppose your shredder may be drawing so much current that the voltage to the modem is going too low. If this is the case, you gotta either get the shredder plugged in closer (resistance wise) to the power company or get a more tolerant supply for the modem.

Bob

Hi Bob,

The voltage isn't dropping... otherwise the modem would reboot... it just loses its mind :-)

Unplugging and re-plugging its wall-wart fixes it.

It's also close to a wall panel where a bunch of CAT-5 is routed :-( I'm all hard-wired here using a LinkSys Barricade Router to other rooms in the house.

I'll try a filter... then maybe re-think my furniture arrangement :-) ...Jim Thompson

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=A0 =A0 ...Jim Thompson

=A0 =A0| =A0 =A0mens =A0 =A0 |

=A0 | =A0 =A0 et =A0 =A0 =A0|

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When in doubt, filter the lowest power device, noting that the load is really the R in a LRC circuit. Lower current, higher R. Thus I would filter the source to the modem, preferably after the wall wart.

I've found some of these switcher wall warts work about as well as the home brew 555 based converters you see on board too cheap to buy good controller chips. Often replacing the wall wart solves interference/ regulation problems.

I came across the proton spr-218l-05 in a local surplus shop and found it to be a really decent switcher. I went back and wiped out the stock, which wasn't a big deal at $5 each. ;-) Anyway, you might try using some other regulated wall warts you have handy, preferably from Japan or Taiwan.

in

moving the shredder to another room ?:-)

check to see if the problem occurs when the shredder __runs__

or when it switches on and off.... maybe you need a snubber across the switch..

Mark

The cable-TV coaxial cable shield is typically grounded at several places.

If the cable modem is connected to the mains using a 3 wire cable, the cable modem signal ground may be connected to the mains Ground/Earth wire and finally to the house grounding electrode at the service entry.

On the cable modem, check if there is a DC (or LF) conductivity between the mains Earth/Ground terminal and coaxial cable socket shield.

In such cases, a small part of the shredder high frequency noise current may flow through the cable modem PCB into the cable operator remote ground (due to common impedances in TN-C-S electric distribution systems) causing havoc on the PCB. Breaking this DC and low frequency conductivity path between the cable modem and the actual coaxial cable (e.g. using RF isolation transformer 75:75 ohms) will cut the DC and LF current through the cable modem.

I've never seen a cable modem with a three wire cord in the US. All either used a wallwart or a two wire cord.

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Try a ISOBAR, with filtering.

We filtered out some hash for a timeclock at the last place I worked.

Cheers

WallWart here. ...Jim Thompson

In UK, we have plug-in adaptors and multi-ways that will suppress RFI.

In fact, they're often 'good' enough to kill thru-the-mains networking...

Uh, can you try clipping on a ferrite block, or Ham's trick of wrapping power lead through a ferrite ring ?? Latter may need replacing moulded-on plug...

FWIW, my original computer, an Apple ][+, was often zapped when our central heating cycled. I added a hifi-grade line suppressor to the Apple's wall-plug. Its hefty toroidal choke did the trick...

Of course, my plastic-cased Apple radiated *all over* the district. Local CB users learned to avoid our street. Then a neighbour rang me to mention the persistent bug he'd seen in my 3D Astronomy program. Seems my TV modulator leaked, too...

Thirty years on, the local aether is again polluted: Running a sweep with Spouse's lap-top's sniffer shows four regular WiFi routers. Happens they're all encrypted...

--------------------------------------- Posted through

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

I'd bet that it's conducted EMI. In such cases I've specified a Triplite Isobar premium power strip. Extensive EMI isolation and filtering between adjacent outlets.

If you feel that it's a radiated problem. just try to route the cable more than a couple of feet away from the shredder's power cord. Sometimes you get lucky with a clip-on ferrite. Oppie

Like my Scientific Atlanta, and the Tosiba I used to have. The RCA's are all oddball two wire AC cords.

I'd suggest building yourself a filter-box. Use one of the nice metal-case CLC common-and-differential-mode powerline filter modules... I usually think of Corcom when I think of these, but they're made by quite a few companies.

Build it into a large outlet box, along with a fuse (or breaker) and a line cord. Plug the filter-box into the power strip and plug the shredder into the filter.

Alternatively, build one right into the shredder - mount it inside the chassis right where the power cord enters the cabinet, and wire it into the circuit at this point.

These things can be quite good at snubbing out conducted interference from noisy motors, etc.

Yep. Some devices utilize bypass caps mounted directly on the motor terminals to ground.

Its possible that Jim's shredder might have had caps at one time, but some event lead to them losing their magic smoke.

Or vibrated enough to fall off the pc board from either cracked solder joints or metal fatigue.

He could have a motor that's about to fail, as well. I've scrapped some shreaders and the motors were barely up to the job. The cutters were still razor sharp, but the cheap gears were broken and the motors needed new brushes.

That's possible. Bad brushes arc and create more noise.