Capacitor Discharge Leads – for Microwave use

[Hollytree_Technical]

Hi all

Just wondering where it is possible to get capacitor discharge leads that are suitable for microwave use. Failing that I have actually got a couple of suitable probes that I could use to build my own but not sure what would be a suitable resistance to use (What resistance are the bought ones?).

I would also like to lay my hands on a neon test block for putting into the microwave.

If anyone could help with either of those queries it would be much appreciated.

Jem

[admin]

Re: Capacitor Discharge Leads – for Microwave use

long nose pliers’..lol Or a wet finger

[BobHope]

Re: Capacitor Discharge Leads – for Microwave use

For the high voltage capacitor in a microwave oven, use a 100 K ohm 25 W or larger resistor with a clip lead to the metal chassis. The reason to use a large (high wattage) resistor is again not so much power dissipation as voltage hold off. You don’t want the HV zapping across the terminals of the resistor.and encase the resiator in heat shrink sleaving. Clip the ground wire to an unpainted spot on the chassis. Use the discharge probe on each side of the capacitor in turn for a second or two, Since the time constant RC is about .1 second, this should drain the charge quickly and safely

Bob.

[jimca007]

Re: Capacitor Discharge Leads – for Microwave use

yep better with a discharge resistor we always zapped them with insulated long nose pliers until I was told on a course this can and does damage the cap, not always but has the potential to. Also the chance of the plier insulation gettin torn in your tool box and you not noticing leaving you with a conductive surface to grip… funny how many things have changed safety wise over the last 20 years… mains neon testers, rolls of black tape…..

[eastlmark]

Re: Capacitor Discharge Leads – for Microwave use

In 30 years of servicing microwaves I have never used either of the requested items. Unless you are dealing with commercial stuff (in which case ignore me), all domestic microwaves caps have discharge resistors built in for the last 20 years or so, so a quick screwdriver across the terminals will prove it is discharged without any damage (if the resisitor is faulty then the cap has had it anyway so there is nothing to loose). as for the neon tester…nothing but a gimick to impress the customer with.

[microgerry]

Re: Capacitor Discharge Leads – for Microwave use

Have you tried Magsells on the Isle Of Wight? Thay may have both

[jimca007]

Re: Capacitor Discharge Leads – for Microwave use

Taken from IEE safety guidlines:
Reasons to use a resistor and not a screwdriver to discharge capacitors:

It will not destroy screwdrivers and capacitor terminals.
It will not damage the capacitor (due to the current pulse).The pulse generated will almost certainly cause some break down of the dielectric and could cause capacitor failure.
It will reduce your customers stress level in not having to hear those scary snaps and crackles.

[Martin]

Re: Capacitor Discharge Leads – for Microwave use

BobHope wrote:Use the discharge probe on each side of the capacitor in turn for a second or two, Since the time constant RC is about .1 second, this should drain the charge quickly and safely

[admin]

Re: Capacitor Discharge Leads – for Microwave use

I still say a wet finger is the best way..

Checks that it’s holding power also. :rolls:

Saves going for a 10 mile run as it’ll increase your heart rate without having to get changed… :clown:

Bryan

[Allsorts]

Re: Capacitor Discharge Leads – for Microwave use

Martin wrote:

BobHope wrote:
Use the discharge probe on each side of the capacitor in turn for a second or two, Since the time constant RC is about .1 second, this should drain the charge quickly and safely

I thought that clip was to be put on the chassis of the microwave… the same way we used to discharge the tube of a CRT TV. Good job I don’t meddle with microwaves isn’t it.

George

[Author]

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