Brian, Littlefuse has a whole line of varistors. Go to www.mouser.com, and enter the following part numbers:
v130LA10a v130LA20a v250LA20a The 10, or 20 in the p/n specifies the diameter in mm for the part. The 130 or 250 is for the rated RMS voltage the varistor is designed to protect. The larger diameter has higher Joule capability. Look at the data sheets relating clamping voltage versus current through the device. These items offer some protection for your equipment, BUT these are only one component towards protecting your equipment from power line transients. They are intended to suppress the once in a while transient, and are not intended to be working repetively since they will warm up, and eventually be another toasted charcoal brick. Other things to consider are ferrite beads, common mode transformers, feed through capacitors, bypass capacitors, etc. Most if not all of these items are used on computer power supplies where the input 120 vac is converted to DC. Sometimes you can "saws-all" the filter off a computer power supply, and use that for protecting ham gear of similar power ratings (< 250 watts). Jim --- [EMAIL PROTECTED] wrote: > Noit sure Don - a fellow ham traded these to me. > They are black disks and look pretty much like a > large > ceramic capacitor, if you can imagine... > > They are marked: > STM and CL-30 > > I think the resistance at rest is about 3 to 5 ohms. > > On 30 Oct 2005 at 9:24, Rev. Don Sanders wrote: > > > OK Bry, You got my interest. What is the part > number and are they from > > Mouser? I know I need several for my boatanchors > and my 2 Astrons(20 and 35 > > amp). > > > > Healthfully yours, > > DON W4BWS > > ----- Original Message ----- > > From: <[EMAIL PROTECTED]> > > To: "Discussion of AM Radio" > <amradio@mailman.qth.net> > > Sent: Sunday, October 30, 2005 7:27 AM > > Subject: Re: [AMRadio] High Voltage Power Supplies > > > > > > > On 30 Oct 2005 at 9:08, Ed Swynar wrote: > > > > > > > Is this the reult of transients / voltage > spikes somehow "overwhelming" > > > > the diodes...? > > > > > > Probably - why not try one of those transient > suppressors (varistor I > > think) > > > on the primary side of your power tranny? > > > I just put one in my Astron 35M and it > eliminated the "THUNK!" > > > at power-on. > > > > > > A number of guys have put them into Johnson > xmtrs with similar > > improvement. > > > Maybe it could save your diode strings. > > > > > > Do you have a capacitor-input filter on the > p.s.u.? > > > Choke input filters tend to be a bit kinder to > the rectifiers. > > > > > > 73 de AF4K, Bry > > > > > > > ______________________________________________________________ > > > AMRadio mailing list > > > Home: > http://mailman.qth.net/mailman/listinfo/amradio > > > Help: http://mailman.qth.net/mmfaq.html > > > Post: mailto:AMRadio@mailman.qth.net > > > AMfone Website: http://www.amfone.net > > > AM List Admin: Brian Sherrod/w5ami > > > > > > > > > > ______________________________________________________________ > > AMRadio mailing list > > Home: > http://mailman.qth.net/mailman/listinfo/amradio > > Help: http://mailman.qth.net/mmfaq.html > > Post: mailto:AMRadio@mailman.qth.net > > AMfone Website: http://www.amfone.net > > AM List Admin: Brian Sherrod/w5ami > > > ______________________________________________________________ > AMRadio mailing list > Home: > http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami >
