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  #1  
Old 09-17-2017, 09:08 AM
tc1961 tc1961 is offline
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Question about discharging things before working on TV

Can someone please provide a source of info or an answer to making sure components are safely discharged before your hands go into a TV chassis?

Would it be something like:

With the TV unplugged,

Using a well insulated screwdriver and a grounding clip on the shaft, grounded to the chassis, slide the screwdriver under the HV connection on the tube until you get a spark.

Short the terminals of all can style electrolytic capacitors.

Anything else?
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Old 09-17-2017, 09:40 AM
walterbeers walterbeers is offline
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Sounds correct to me. Take a clip lead and clip one end of the wire to a thin screwdriver and the other end to the chassis ground and slide it under the suction cup, HV wire that connects to the side or top of the CRT. Might do it several times as CRTs have a tendency to rebuild some residual charge. Never had a problem with electrolytic caps as the change on them usually drains off by itself, but it sure doesn't hurt to ground the terminals on them as well just in case. Don't worry, it won't kill you, but it can give you a nasty jolt. Most of the time you get zapped and you jerk your hand and arm out of the set skinning your hand or arms.
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Old 09-17-2017, 10:34 AM
madlabs madlabs is offline
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If you want to be real careful, put a 1 Mohm resistor in series to ground. Prevents big sparks/currents and is easier on caps when discharging them.
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Old 09-17-2017, 11:33 AM
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Findm-Keepm Findm-Keepm is offline
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Quote:
Originally Posted by madlabs View Post
If you want to be real careful, put a 1 Mohm resistor in series to ground. Prevents big sparks/currents and is easier on caps when discharging them.
With some large (100uF) capacitors, the R-C discharge time with a 1 Megohm resistor could be over a minute.

Pomona Electronics made a 40KV discharge set (lucite handle, cooper bronze shank with swappable probe, hook, and balled ends) for the Navy - they used a 5K series resistor. That kept the RC time for discharge under 6 seconds for just about everything. Not sure of the composition/wattage of the resistor, but we had to megger it as a daily test. Me, I'd use a 2 Watt Carbon Comp in series, say 5100 or 5600 ohms, standard values.

450V discharging through a 5K resistor to ground keeps it under 100mA at all times on the discharge curve - no sparky-sparky at all.

Or, if you want to visually see the discharge effects, build one of these:

http://jestineyong.com/build-your-ow...scharge-probe/

Has LEDs that indicate if there is still voltage present.
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Last edited by Findm-Keepm; 09-17-2017 at 11:39 AM. Reason: Added link/info
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Old 09-17-2017, 06:03 PM
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Ed in Tx Ed in Tx is offline
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I keep a 150 Ohm 2W resistor with a lead and clip on one end for this purpose. Low enough Ohms to discharge quickly but little or no sparking. 2W because it's big enough to handle and the leads are heavy duty. Not discharging CRTs though. Mainly switching power supplies, making sure the primary side isn't charged up before I start testing capacitors with my ESR meter.

Last edited by Ed in Tx; 09-17-2017 at 06:10 PM.
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  #6  
Old 12-07-2017, 03:11 PM
user181 user181 is offline
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For a modern CRT set with a plastic case, where would you connect the ground lead to discharge the CRT?
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Old 12-07-2017, 03:13 PM
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N2IXK N2IXK is offline
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Quote:
Originally Posted by user181 View Post
For a modern CRT set with a plastic case, where would you connect the ground lead to discharge the CRT?
Connect to the grounding strap/braid that is in contact with the CRT dag coating.
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Old 12-08-2017, 08:15 AM
kf4rca kf4rca is offline
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I just use 2 screwdrivers. Put one on the aquadag and the other on the HV button, then bring the two screwdrivers together till they touch.
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